CSC suppress immune response against brain tumor

Cancer stem cells suppress immune response against brain tumor, News Release, The University of Texas M. D. Anderson Cancer Center, January 15, 2010.

About two publications, one in Clin Cancer Res 2010(Jan 15);16(2):461-73 and the other in Mol Cancer Ther 2010(Jan);9(1):67-78.

See also: Cancer stem cells suppress immune response against brain tumor, Science Blog, January 15, 2010, and, Mechanism that helps brain cancer evade immune system attack discovered, Science News, January 16, 2010.

CD133 and poorer prognosis in locally advanced colon cancer

Higher percentage of CD133+ cells is associated with poor prognosis in colon carcinoma patients with stage IIIB by Chun-Yan Li and 11 co-authors, including Xiao-Shi Zhang, J Transl Med 2009(Jul 7); 7: 56. [Full text via Libre OA][PMC version of the full text][PubMed Abstract] Final paragraph of the Abstract:

CONCLUSION: The fact that a higher percentage CD133+ cells were strongly associated with a poorer prognosis in patients with locally advanced colon cancer implicated that CD133+ cancer cells contribute to the tumor progression, and the overpopulation hypothesis of cancer stem cell seems reasonable.

CD133 expression has high prognostic impact for colon cancer

The cancer stem cell marker CD133 has high prognostic impact but unknown functional relevance for the metastasis of human colon cancer by David Horst and 6 co-authors, including Thomas Kirchner and Andreas Jung, J Pathol 2009(Jun 25) [Epub ahead of print] PubMed Abstract:

In colon cancer, CD133 has recently been used to enrich for a subset of tumour cells with tumour-initiating capabilities and was therefore suggested to mark colon cancer stem cells. However, this molecule has surprisingly been shown to lack functional importance for tumour initiation itself. Herein, we investigated whether CD133 may be relevant for colon cancer metastasis in patients, and as metastasis requires several additional biological characteristics besides tumour initiation, we examined the effects of knocking down CD133 expression in colon cancer cell lines on proliferation, migration, invasion, and colony formation. We demonstrate that high CD133 expression correlates strongly with synchronous liver metastasis in a matched case-control collection, while siRNA-mediated knock down of this factor has no significant effect on the mentioned biological characteristics. Thus, we conclude that CD133 expression is a marker with high prognostic impact for colon cancer, while it seems to have no obvious functional role as a driving force of this malignancy.

More on immune based therapies for the treatment of cancers

ImmunoCellular Therapeutics Retains Services of Torrey Pines Institute for Molecular Studies and Renowned Immunologist to Evaluate Lead Product Candidate, Business Wire, July 14, 2009. Excerpts:

ImmunoCellular Therapeutics, Ltd. (OTCBB: IMUC), a clinical-stage biotechnology company that is developing immune based therapies for the treatment of brain and other cancers, announced today that it has retained the services of the Torrey Pines Institute for Molecular Studies in San Diego, CA, to evaluate the immunogenicity of peptides to target cancer stem cells (CSC’s) relating to the Company’s lead product candidate ICT-121. The evaluation will be conducted by Dr. Clemencia Pinilla, a specialist in immune response mechanisms and their role in the prevention and cause of human disease with over 100 publications and multiple patents to her credit.

.....

ICT-121 is IMUC’s cancer stem cell (CSC) vaccine product candidate that consists of a peptide to stimulate a cytotoxic T-lymphocyte (CTL) response to CD133, which is generally overexpressed on the CSCs.

Relevant links: Profile of Clemencia Pinilla, of the Torrey Pines Institute for Molecular Studies in San Diego, California; and, Opinion: A Stem of Hope for Cancer Treatments by Manish Singh (President and CEO of IMUC), Genetic Engineering & Biotechnology News, June 12, 2009. [Previous blog post: Bright future for CSC therapies?, June 14, 2009].

Note that it is important that CSC-targeted vaccination "should not lead to immune reaction to normal cells that may express common antigens". For a recent publication from which this quotation is taken, see: Antigen-Specific T Cell Response from Dendritic Cell Vaccination Using Cancer Stem-like Cell-Associated Antigens by Qijin Xu and 8 co-authors, including John S Yu, Stem Cells 2009(Apr 23) [Epub ahead of print][PubMed Citation]. (John S Yu is Chief Scientific Officer and Chairman of the Board of IMUC, see: Our Team - IMUC).

For some background about immune based therapies for the treatment of cancer, see: Cancer Vaccines by Preeti Gokal Kochar, ProQuest Discovery Guide, January 2006.

See also: Connotea bookmarks matching tag CD133.

About CD133 as a marker for CSC

CD133 as a marker for cancer stem cells: progresses and concerns by Yaojiong Wu, Philip Yuguang Wu, Stem Cells Dev 2009(May 2) [Epub ahead of print][ResearchGATE entry][FriendFeed entry] PubMed Abstract:

Increasing evidence supports the cancer stem cell hypothesis, which postulates that cancer stem cells are responsible for tumor initiation, metastasis and resistance to treatments. Therefore, they are the cells to target to cure a cancer. To study the behavior of cancer stem cells, markers for prospective isolation of cancer stem cells are crucial. Recently, CD133 has been used extensively as a marker for the identification of stem cells from normal and cancerous tissues. Several more recent studies, however, indicate that CD133 are expressed in differentiated epithelial cells in various organs, and CD133-negative cancer cells can also initiate tumors. The findings suggest that CD133 is not restricted to somatic stem cells and cancer stem cells. However, in many cases CD133 may be used in combination with other markers or methods to acquire stem cells. In this review, we summarize findings in CD133 expression in various tissues and critically discuss its applications in stem cell isolation.

Neoplastic transformation of intestinal SC

Cancer stem cells: Can mutated stem cells produce tumours? by Nicola McCarthy, Nat Rev Cancer 2009(Feb); 9(2): 74 [full text accessible after free registration]. Last sentence:

Both papers indicate that a single mutation in normal intestinal stem cells can give rise to tumours, as has been suggested. It is interesting that, although LGR5 and PROM1 seem to mark similar stem cells in the small intestine, PROM1 does not mark colonic stem cells, whereas LGR5 does. This illustrates the need to clearly define markers and their limitations if we are to begin to understand the contribution of normal tissue stem cells and cancer stem cells to tumorigenesis.

The two papers referred to are these [neither are publicly accessible]:

1) Crypt stem cells as the cells-of-origin of intestinal cancer by Nick Barker and 9 co-authors, including Hans Clevers, Nature 2008(Dec 17) [Epub ahead of print][PubMed Citation].

2) Prominin 1 marks intestinal stem cells that are susceptible to neoplastic transformation by Liqin Zhu and 9 co-authors, including Richard Gilbertson, Nature 2008(Dec 17) [Epub ahead of print][PubMed Citation].

See also this blog post: Two articles linking normal intestinal SC to CSC, December 18, 2008.

Prognostic potential of CSC analysis in glioblastoma

Cancer stem cell analysis and clinical outcome in patients with glioblastoma multiforme by Roberto Pallini and 10 co-authors, including Ruggero De Maria, Clin Cancer Res 2008(Dec 15); 14(24): 8205-12. PubMed Abstract:

PURPOSE: Cancer stem cells (CSC) are thought to represent the population of tumorigenic cells responsible for tumor development. The stem cell antigen CD133 identifies such a tumorigenic population in a subset of glioblastoma patients. We conducted a prospective study to explore the prognostic potential of CSC analysis in glioblastoma patients. EXPERIMENTAL DESIGN: We investigated the relationship between the in vitro growth potential of glioblastoma CSCs and patient death or disease progression in tumors of 44 consecutive glioblastoma patients treated with complete or partial tumorectomy followed by radiotherapy combined with temozolomide treatment. Moreover, we evaluated by immunohistochemistry and immunofluorescence the prognostic value of the relative presence of CD133(+) and CD133(+)/Ki67(+) cells in patient tumors. RESULTS: In vitro CSC generation and the presence of >/=2% CD133(+) cells in tumor lesions negatively correlated with overall (P = 0.0001 and 0.02, respectively) and progression-free (P = 0.0002 and 0.01, respectively) survival of patients. A very poor overall (P = 0.007) and progression-free (P = 0.001) survival was observed among patients whose tumors contained CD133(+) cells expressing Ki67. Taking into account symptom duration, surgery type, age, O(6)-methylguanine-DNA methyltransferase promoter methylation, and p53 status, generation of CSCs and CD133/Ki67 coexpression emerged as highly significant independent prognostic factors, with an adjusted hazard ratio of 2.92 (95% confidence interval, 1.37-6.2; P = 0.005) and 4.48 (95% confidence interval, 1.68-11.9; P = 0.003), respectively. CONCLUSIONS: The analysis of CSCs may predict the survival of glioblastoma patients. In vitro CSC generation and presence of CD133(+)/Ki67(+) cells are two considerable prognostic factors of disease progression and poor clinical outcome.

See also: Prognostic relevance of SOCS3 hypermethylation in patients with glioblastoma multiforme by Maurizio Martini and 5 co-authors, including Luigi Maria Larocca, Int J Cancer 2008(Dec 15); 123(12): 2955-60 [Epub 2008(Sep 3)][PubMed Citation].

[The full text of these articles isn't publicly accessible].

Two articles linking normal intestinal SC to CSC

1) Crypt stem cells as the cells-of-origin of intestinal cancer by Nick Barker and 9 co-authors, including Owen J Sansom and Hans Clevers, Nature 2008(Dec17) [Epub ahead of print]. Abstract:

Intestinal cancer is initiated by Wnt-pathway-activating mutations in genes such as adenomatous polyposis coli (APC). As in most cancers, the cell of origin has remained elusive. In a previously established Lgr5 (leucine-rich-repeat containing G-protein-coupled receptor 5) knockin mouse model, a tamoxifen-inducible Cre recombinase is expressed in long-lived intestinal stem cells[reference 1]. Here we show that deletion of Apc in these stem cells leads to their transformation within days. Transformed stem cells remain located at crypt bottoms, while fuelling a growing microadenoma. These microadenomas show unimpeded growth and develop into macroscopic adenomas within 3-5weeks. The distribution of Lgr5+ cells within stem-cell-derived adenomas indicates that a stem cell/progenitor cell hierarchy is maintained in early neoplastic lesions. When Apc is deleted in short-lived transit-amplifying cells using a different cre mouse, the growth of the induced microadenomas rapidly stalls. Even after 30weeks, large adenomas are very rare in these mice. We conclude that stem-cell-specific loss of Apc results in progressively growing neoplasia.

See also: Tracking down bowel cancer stem cells by Kat Arney, Science Update Blog, Cancer Research UK, December 17, 2008. Excerpt:

More experiments need to be done before we know for sure whether stem cells play a vital role in human bowel cancer. For now, these results are a promising step in the right direction – and a confirmation that the stem cell theory may well hold true for at least one type of cancer.

If we can understand more about the molecular pathways that control cancer, we can start to design new, more effective ways to prevent and treat the disease.

2) Prominin 1 marks intestinal stem cells that are susceptible to neoplastic transformation by Liqin Zhu and 9 co-authors, including Richard J Gilbertson, Nature 2008(Dec17) [Epub ahead of print]. Abstract:

Cancer stem cells are remarkably similar to normal stem cells: both self-renew, are multipotent and express common surface markers, for example, prominin 1 (PROM1, also called CD133)[reference 1]. What remains unclear is whether cancer stem cells are the direct progeny of mutated stem cells or more mature cells that reacquire stem cell properties during tumour formation. Answering this question will require knowledge of whether normal stem cells are susceptible to cancer-causing mutations; however, this has proved difficult to test because the identity of most adult tissue stem cells is not known. Here, using an inducible Cre, nuclear LacZ reporter allele knocked into the Prom1 locus (Prom1^C-L), we show that Prom1 is expressed in a variety of developing and adult tissues. Lineage-tracing studies of adult Prom1^+/C-L mice containing the Rosa26-YFP reporter allele showed that Prom1⁺ cells are located at the base of crypts in the small intestine, co-express Lgr5 [reference 2], generate the entire intestinal epithelium, and are therefore the small intestinal stem cell. Prom1 was reported recently to mark cancer stem cells of human intestinal tumours that arise frequently as a consequence of aberrant wingless (Wnt) signalling[references 3, 4, 5]. Activation of endogenous Wnt signalling in Prom1^+/C-L mice containing a Cre-dependent mutant allele of beta-catenin (Ctnnb1^lox(ex3)) resulted in a gross disruption of crypt architecture and a disproportionate expansion of Prom1 cells at the crypt base. Lineage tracing demonstrated that the progeny of these cells replaced the mucosa of the entire small intestine with neoplastic tissue that was characterized by focal high-grade intraepithelial neoplasia and crypt adenoma formation. Although all neoplastic cells arose from Prom1⁺ cells in these mice, only 7% of tumour cells retained Prom1 expression. Our data indicate that Prom1 marks stem cells in the adult small intestine that are susceptible to transformation into tumours retaining a fraction of mutant Prom1⁺ tumour cells.

See also: Molecular marker identifies normal stem cells as intestinal tumor source, News Release, St. Jude Children's Research Hospital, December 17, 2008. Excerpt:

Scientists at St. Jude Children’s Research Hospital have answered a central question in cancer biology: whether normal stem cells can give rise to tumors. Stem cells are immature cells that can renew themselves and give rise to mature differentiated cells that compose the range of body tissues. In recent years, researchers have developed evidence that cancers may arise from mutant forms of stem cells.

c-Myc required for maintenance of glioma CSC

c-Myc is required for maintenance of glioma cancer stem cells by Jialiang Wang and 7 co-authors, including Jeremy N Rich, PLoS ONE 2008(Nov 20); 3(11): e3769. [PMCID: PMC2582454]. Abstract:

Background

Malignant gliomas rank among the most lethal cancers. Gliomas display a striking cellular heterogeneity with a hierarchy of differentiation states. Recent studies support the existence of cancer stem cells in gliomas that are functionally defined by their capacity for extensive self-renewal and formation of secondary tumors that phenocopy the original tumors. As the c-Myc oncoprotein has recognized roles in normal stem cell biology, we hypothesized that c-Myc may contribute to cancer stem cell biology as these cells share characteristics with normal stem cells.

Methodology/Principal Findings

Based on previous methods that we and others have employed, tumor cell populations were enriched or depleted for cancer stem cells using the stem cell marker CD133 (Prominin-1). We characterized c-Myc expression in matched tumor cell populations using real time PCR, immunoblotting, immunofluorescence and flow cytometry. Here we report that c-Myc is highly expressed in glioma cancer stem cells relative to non-stem glioma cells. To interrogate the significance of c-Myc expression in glioma cancer stem cells, we targeted its expression using lentivirally transduced short hairpin RNA (shRNA). Knockdown of c-Myc in glioma cancer stem cells reduced proliferation with concomitant cell cycle arrest in the G0/G1 phase and increased apoptosis. Non-stem glioma cells displayed limited dependence on c-Myc expression for survival and proliferation. Further, glioma cancer stem cells with decreased c-Myc levels failed to form neurospheres in vitro or tumors when xenotransplanted into the brains of immunocompromised mice.

Conclusions/Significance

These findings support a central role of c-Myc in regulating proliferation and survival of glioma cancer stem cells. Targeting core stem cell pathways may offer improved therapeutic approaches for advanced cancers.

The full text is openly accessible.

Liver progenitor cell population with CSC phenotype

Expansion of CD133 expressing liver cancer stem cells in liver specific PTEN deleted mice by C Bart Rountree, Wei Ding, Lina He, Bangyan Stiles, Stem Cells 2008(Nov 13). [Epub ahead of print]. PubMed Abstract:

Background: PTEN (phosphatase and tensin homologue deleted on chromosome 10) is a lipid phosphatase that regulates mitogenic signaling pathways, and deficiency of PTEN results in cell proliferation, survival, and malignancy. Murine liver specific Pten deletion models develop liver malignancy by twelve months of age. Using this model, we describe a population of CD133+ liver cancer stem cells isolated during the chronic injury phase of disease progression and before primary carcinoma formation. Methods: We performed immunohistochemistry and flow cytometry isolation using livers from 3 and 6-monthold Pten(loxp/loxp); Alb-Cre+ mice (Mutants) and controls. CD133+CD45- non-parenchymal (NP) cells were analyzed for gene expression profile and protein levels. Single CD133+CD45- oval cells were isolated for clonal expansion and tumor analysis. Cultured and freshly isolated liver CD133+CD45- and CD133-CD45- NP cells were injected into immune-deficient and immune-competent mice. Results: In Mutant mice, the NP fraction increases in CD133+CD45- cells in 3 and 6-month Pten deleted animals compared to controls. Clone lines expanded from single CD133+CD45- cells demonstrated consistent liver progenitor cell phenotype, with bi-lineage gene expression of hepatocyte and cholangiocyte markers. CD133+ cells from expanded clone lines formed robust tumors in immune-deficient and immune-competent mice. Furthermore, freshly isolated CD133+CD45- NP liver cells from six month-old Mutants formed tumors invivo, and CD133-CD45- NP cells did not. Consistent with a cancer stem cell phenotype, CD133+ cells demonstrate resistance to chemotherapy agents compared to CD133- cells. Conclusions: CD133+CD45- non-parenchymal cells from chronic injury Pten(loxp/loxp); Alb-Cre+ mice represent a bi-potent liver progenitor cell population with cancer stem cell phenotype.

The full text of this article is openly accessible [PDF].

CD133 is a marker of bioenergetic stress in human glioma

CD133 is a marker of bioenergetic stress in human glioma by Corinne E Griguer and 6 co-authors, including G Yancey Gillespie, PLoS ONE 2008; 3(11): e3655. Epub 2008 Nov 5. PubMed Abstract:

Mitochondria dysfunction and hypoxic microenvironment are hallmarks of cancer cell biology. Recently, many studies have focused on isolation of brain cancer stem cells using CD133 expression. In this study, we investigated whether CD133 expression is regulated by bioenergetic stresses affecting mitochondrial functions in human glioma cells. First, we determined that hypoxia induced a reversible up-regulation of CD133 expression. Second, mitochondrial dysfunction through pharmacological inhibition of the Electron Transport Chain (ETC) produced an up-regulation of CD133 expression that was inversely correlated with changes in mitochondrial membrane potential. Third, generation of stable glioma cells depleted of mitochondrial DNA showed significant and stable increases in CD133 expression. These glioma cells, termed rho(0) or rho(0), are characterized by an exaggerated, uncoupled glycolytic phenotype and by constitutive and stable up-regulation of CD133 through many cell passages. Moreover, these rho(0) cells display the ability to form "tumor spheroids" in serumless medium and are positive for CD133 and the neural progenitor cell marker, nestin. Under differentiating conditions, rho(0) cells expressed multi-lineage properties. Reversibility of CD133 expression was demonstrated by transfering parental mitochondria to rho(0) cells resulting in stable trans-mitochondrial "cybrid" clones. This study provides a novel mechanistic insight about the regulation of CD133 by environmental conditions (hypoxia) and mitochondrial dysfunction (genetic and chemical). Considering these new findings, the concept that CD133 is a marker of brain tumor stem cells may need to be revised.

Excerpts from the Discussion section of the full text (openly accessible):

Figure 7. Tumor progression model

Last paragraph:

We described here that hypoxia and modification of the bioenergetic status of glioma cells govern the regulation of CD133 at post-transcriptional level. Data presented here strongly indicated that changes in the cellular environment that results in alteration of mitochondrial function are responsible for the enhanced up-regulation of CD133 antigen in glioma cells, suggesting that CD133 expression in human glioma cells is not obligatory relative to the stem cell phenotype but rather, reveals the occurrence of a stress response.

Two publications on colorectal cancer stem cells

1) Colon cancer stem cells: implications for prevention and therapy by Emina H Huang and Max S Wicha, Trends Mol Med 2008(Nov); 14(11): 503-9. Epub 2008 Oct 17. Pubmed Abstract:

The recent identification of colon cancer tumor-initiating cells adds further support to the cancer stem cell hypothesis. Ongoing basic and translational research efforts are aimed at gaining an increased understanding of the biology of these cells, as well as methods of targeting them. In addition, the relationship between colon carcinogenesis and inflammatory conditions, such as longstanding colitis and inherited syndromes, might be linked to the effect of the processes on stem cells in the colon. This review summarizes current literature on colon cancer stem cells and proposes strategies aimed at targeting these cells for colon cancer prevention and therapy.

From the "Summary" section of the full text (not publicly accessible):

The identification of colon cancer tumor-initiating cells provides further support for the cancer stem cell hypothesis. Future therapy will be directed not only at these rare cells themselves but also at the microenvironment that regulates stem cell behavior. Furthermore, because cancers might originate from disregulation of normal stem cell homeostasis, strategies for cancer prevention might also target this cell population.

2) CD44 is of functional importance for colorectal cancer stem cells by Lei Du and 10 co-authors, including Quan Chen, Clin Cancer Res 2008(Nov 1); 14(21), 6751-60. Abstract:

Purpose: Both CD44 and CD133 were reported as putative markers for isolating colorectal cancer stem cells (CSC). It remains to be resolved if both of these markers are of functional importance for colorectal CSC.

Experimental Design: The expression of CD44 and CD133 in normal colonic tissues and primary colorectal cancer was assessed by immunohistochemistry in a series of 60 patients on tissue microarray sections. Both in vitro clonogenic and in vivo tumorigenic assay were applied to measure CSC activities from the cells isolated from patients. Lentiviral RNA interference was used to stably knock down CD44 or CD133 in colorectal cancer cells from patients.

Results: We found that CD44+ cells displayed clustered growth and they did not colocalize with CD133+ cells within colorectal cancer. As few as 100 CD44+ cells from a patients' tumor initiated a xenograft tumor in vivo. A single CD44+ cell from a tumor could form a sphere in vitro which has characteristic stem cell properties and was able to generate a xenograft tumor resembling the properties of the primary tumor. Knockdown of CD44, but not CD133, strongly prevented clonal formation and inhibited tumorigenicity in xenograft model.

Conclusions: These results indicate that CD44 is a robust marker and is of functional importance for colorectal CSC for cancer initiation.

From the "Translational Relevance" section of the full text (not publicly accessible):

Cancer stem cells (CSC) represent an exciting avenue for cancer study and novel target for drug discovery. In this study, we showed that CD44 was a robust colorectal CSC marker and it is of functional importance for colorectal CSCs using clinic samples and xenograft models. The expression of CD44 and CD133 was assessed in primary tumors and matched normal tissues of patients with colorectal cancer (CRC) by using immunohistochemistry and flow cytometric analysis. We found that CD133 and CD44 did not appear on the same region of tumor tissue and it is infrequent to detect that both markers coexisted in the same cell. Knockdown of CD44 expression by RNA interference or inhibition of its function by specific antibodies could significantly inhibit tumor initiation and development in nude mice. These results indicate that CD44 and its related signaling pathway could be a critical diagnostic and therapeutic target for CRC.

Distinct populations of tumor-initiating cells

Distinct populations of tumor-initiating cells derived from a tumor generated by rat mammary cancer stem cells by Ileana Zucchi and 13 co-authors, including Benjamin G Neel and Renato Dulbecco, Proc Natl Acad Sci USA 2008(Nov 4); 105(44): 16940–45, published ahead of print October 28, 2008. This is an Open Access Article [PDF]. PubMed Abstract:

Tumors derived from rat LA7 cancer stem cells (CSCs) contain a hierarchy of cells with different capacities to generate self-renewing spheres and tubules serially ex vivo and to evoke tumors in vivo. We isolated two morphologically distinct cell types with distinct tumorigenic potential from LA7-evoked tumors: cells with polygonal morphology that are characterized by expression of p21/(WAF1) and p63 and display hallmarks of CSCs and elongated epithelial cells, which generate tumors with far less heterogeneity than LA7 CSCs. Serial transplantation of elongated epithelial cells results in progressive loss of tumorigenic potential; tumor heterogeneity; CD44, E-cadherin, and epithelial cytokeratin expression and increased alpha-smooth muscle actin I and vimentin expression. In contrast, serial transplantation of LA7 CSCs can be performed indefinitely and results in tumors that maintain their heterogeneity, consistent with self-renewal and multilineage differentiation potential. Collectively, our data show that polygonal cells are CSCs, whereas epithelial elongated cells are lineage-committed progenitors with tumorigenic potential, and suggest that tumor progenitors, although lacking indefinite self-renewal potential, nevertheless may make a substantial contribution to tumor development. Because LA7 cells can switch between conditions that favor maintenance of pure CSCs vs. differentiation into other tumor cell types, this cell system provides the opportunity to study factors that influence CSC self-renewal and differentiation. One factor, p63, was identified as a key gene regulating the transition between CSCs and early progenitor cells.

CD133+ cells within osteosarcoma cell lines

Detection and characterization of CD133+ cancer stem cells in human solid tumours by Virginia Tirino and 8 co-authors, including Gianpaolo Papaccio, PLoS ONE 2008(Oct 21); 3(10): e3469. PubMed Abstract:

BACKGROUND: Osteosarcoma is the most common primary tumour of bone. Solid tumours are made of heterogeneous cell populations, which display different goals and roles in tumour economy. A rather small cell subset can hold or acquire stem potentials, gaining aggressiveness and increasing expectancy of recurrence. The CD133 antigen is a pentaspan membrane glycoprotein, which has been proposed as a cancer stem cell marker, since it has been previously demonstrated to be capable of identifying a cancer initiating subpopulation in brain, colon, melanoma and other solid tumours. Therefore, our aim was to observe the possible presence of cells expressing the CD133 antigen within solid tumour cell lines of osteosarcoma and, then, understand their biological characteristics and performances. METHODOLOGY AND PRINCIPAL FINDINGS: In this study, using SAOS2, MG63 and U2OS, three human sarcoma cell lines isolated from young Caucasian subjects, we were able to identify and characterize, among them, CD133+ cells showing the following features: high proliferation rate, cell cycle detection in a G2\M phase, positivity for Ki-67, and expression of ABCG2 transporters. In addition, at the FACS, we were able to observe the CD133+ cell fraction showing side population profile and forming sphere-clusters in serum-free medium with a high clonogenic efficiency. CONCLUSIONS: Taken together, our findings lead to the thought that we can assume that we have identified, for the first time, CD133+ cells within osteosarcoma cell lines, showing many features of cancer stem cells. This can be of rather interest in order to design new therapies against the bone cancer.

The full text of this article is openly accessible.

Nestin expression in osteosarcomas

Nestin expression in osteosarcomas and derivation of nestin/CD133 positive osteosarcoma cell lines by Renata Veselska, Marketa Hermanova, Tomas Loja, Petr Chlapek, Iva Zambo, Karel Vesely, Karel Zitterbart and Jaroslav Sterba, BMC Cancer 2008(Oct 16); 8(1): 300. PubMed Abstract:

BACKGROUND: Nestin was originally identified as a class VI intermediate filament protein that is expressed in stem cells and progenitor cells in the mammalian CNS during development. This protein is replaced in the adult organism by other intermediate filament proteins; however, nestin may be re-expressed under certain pathological conditions such as ischemia, inflammation, brain injury, and neoplastic transformation. Nestin has been detected in many kinds of tumors, especially in tumors derived from the CNS. Co-expression of nestin and the CD133 surface molecule is considered to be a marker for cancer stem cells in neurogenic tumors. Our work was aimed at a detailed study of nestin expression in osteosarcomas and osteosarcoma-derived cell lines. METHODS: Using immunodetection methods, we examined nestin in tumor tissue samples from 18 patients with osteosarcomas. We also successfully established permanent cell lines from the tumor tissue of 4 patients and immunodetection of nestin and CD133 was performed on these cell lines. RESULTS: Nestin-positive tumor cells were immunohistochemically detected in all of the examined osteosarcomas, but the proportion of these cells that were positively stained as well as the intensity of staining varied. Nestin-positive cells were rarely observed in 2 tumor samples, and the remaining 16 tumor samples showed various nestin expression patterns ranging from very sporadic occurrence to an overwhelming proportion of cells with strong positive staining. Three of the established osteosarcoma cell lines were demonstrated to be nestin-positive, and only one cell line showed no expression of nestin; this finding corresponds with the rare occurrence of nestin-positive cells in the respective tumor sample. Moreover, three of these osteosarcoma cell lines were undoubtedly proven to be Nes+/CD133+. CONCLUSIONS: Our results represent the first evidence of nestin expression in osteosarcomas and suggest the possible occurrence of cells with a stem-like phenotype in these tumors.

The full text is openly accessible.

Found via Nestin expression in osteosarcomas and derivation of nestin/CD133 positive osteosarcoma cell lines, 7thSpace Interactive, October 16, 2008.

CD133 Expression

There's a commentary, "Capturing cancer stem cells", in Nature Medicine 2008(Aug); 14(8): 814.

It's about reactions to a freely-accessible article entitled: "CD133 expression is not restricted to stem cells, and both CD133+ and CD133- metastatic colon cancer cells initiate tumors", by Sergey V Shmelkov and 19 co-authors, in J Clin Invest. 2008(Jun); 118(6): 2111-20. The final sentence of the abstract of this article:

Collectively, our data suggest that CD133 expression is not restricted to intestinal stem or cancer-initiating cells, and during the metastatic transition, CD133⁺ tumor cells might give rise to the more aggressive CD133^– subset, which is also capable of tumor initiation in NOD/SCID mice.

The commentary in Nature Medicine isn't freely accessible, and has no abstract. It consists mainly of answers to the question: "What do the findings mean for the quest to find and target cancer stem cells?". Answers are provided by Zena Werb, Jeremy Rich and Jeffrey Rosen. Excerpts:

For understanding tumorigenesis and creating therapies, a spectrum of markers may be the answer. [Zena Werb]

No single marker is likely to be absolutely informative, but CD133 has proven repeatedly useful in brain tumor stem cell studies for many research groups. [Jeremy Rich]

[T]he findings do not invalidate previous stem cell work using CD133 antibodies, which recognize a specific epitope that may not be conserved between mice and people. [Jeffrey Rosen]

Other comments about the article by Shmelkov and co-authors, or about the commentary in Nature Medicine, would be welcomed.