Conditioned medium induces generation of side population cells

Pluripotency-associated genes in human nasopharyngeal carcinoma CNE-2 cells are reactivated by a unique epigenetic sub-microenvironment by Jun-Xia Cao and 8 co-authors, including Quentin Liu, BMC Cancer 2010(Feb 25); 10: 68 [PubMed citation][Full text via PMC][Full text from journal (via Libre OA)]. Conclusion section of the Abstract:

To our knowledge, this is the first study to demonstrate that non-SP single-clone cells can be induced to generate a SP phenotype when they are cultured with conditioned medium of macrophage-like cells, which is associated with the reactivation of pluripotency-associated genes.

Differences that separate normal vs cancer SC molecular circuitry

Pluripotent Transcription Factors Possess Distinct Roles in Normal versus Transformed Human Stem Cells by Junfeng Ji, Tamra E Werbowetski-Ogilvie, Bonan Zhong, Seok-Ho Hong and Mickie Bhatia, PLoS ONE 2009(Nov 30); 4(11): e8065 [FriendFeed entry][Full text is publicly accessible (via Libre OA)]. PubMed Abstract:

BACKGROUND: Cancer and normal stem cells (SCs) share proliferative properties of self-renewal and expression of key transcription factors (TFs). Despite similar TF identities, the functional role of specific TFs responsible for retaining SC state has yet to be examined in cancer. METHODOLOGY/PRINCIPAL FINDINGS: Here, we compare the role of Oct4 and Nanog, two-core pluripotent TFs, in transformed (t-hPSCs), and normal human pluripotent stem cells (hPSCs). Unlike normal SCs, self-renewal and survival of t-hPSCs were found to be independent of Oct4. In contrast, t-hPSCs exhibit hypersensitivity to reduction in Nanog and demonstrate complete loss of self-renewal coupled with apoptosis. Dual and sequential knockdown of Oct4 and Nanog revealed that sensitivity of t-hPSCs to Nanog was Oct4 dependent. CONCLUSIONS/SIGNIFICANCE: Our study indicates a bifurcation for the role of two-core SC and cancer related TFs in self-renewal and survival processes. We suggest that the divergent roles of these TFs establish a paradigm to develop novel therapeutics towards selective destruction of aggressive tumors harboring cancer stem cells (CSCs) with similar molecular signatures.

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.

Chemosensitization of AML

Another nail in the AML coffin by Camille N Abboud, Blood 2009(Jun 11); 113(24): 6045-6. Editorial [Full text is currently publicly accessible][PubMed Citation]. First paragraph:

In this issue of Blood, Nervi and colleagues and Zeng and colleagues independently report similar findings in both in vitro and in vivo AML models, showing chemosensitization by blocking CXCR4/CXCL12 (SDF-1{alpha}:stromal cell–derived factor 1) signaling using novel CXCR4 antagonist bicyclams, namely AMD3100 (plerixafor) and AMD3465.

Excerpt from the final paragraph:

Finally, while both reports open new avenues for overcoming in vivo drug resistance in AML, it is yet unclear whether durable complete remissions can ensue from this strategy. AML is indeed a very heterogenous disease, and successful eradication of leukemic stem/progenitor cells will require blocking multiple receptors/pathways ...

The two articles discussed in this editorial are:

1) Chemosensitization of acute myeloid leukemia (AML) following mobilization by the CXCR4 antagonist AMD3100 by Bruno Nervi and 10 co-authors, including Timothy J Ley, and John F DiPersio, Blood 2009(Jun 11); 113(24): 6206-14 [Epub 2008(Dec 2)]. [PubMed Citation].

2) Targeting the leukemia microenvironment by CXCR4 inhibition overcomes resistance to kinase inhibitors and chemotherapy in AML by Zhihong Zeng and 12 co-authors, Blood 2009(Jun 11); 113(24): 6215-24 [Epub 2008(Oct 27)]. [PubMed Citation][FriendFeed entry].

[Only the abstracts of these two articles are currently publicly accessible].

Targeting tumorogenic cells in neuroblastoma cell lines

Neuroblastoma Cell Lines Contain Pluripotent Tumor Initiating Cells That Are Susceptible to a Targeted Oncolytic Virus by Yonatan Y Mahller and 8 co-authors, including Timothy P Cripe, PLoS ONE 2009; 4(1): e4235 [Epub 2009 Jan 21]. [The full text is openly accessible]. PubMed Abstract:

BACKGROUND: Although disease remission can frequently be achieved for patients with neuroblastoma, relapse is common. The cancer stem cell theory suggests that rare tumorigenic cells, resistant to conventional therapy, are responsible for relapse. If true for neuroblastoma, improved cure rates may only be achieved via identification and therapeutic targeting of the neuroblastoma tumor initiating cell. Based on cues from normal stem cells, evidence for tumor populating progenitor cells has been found in a variety of cancers. METHODOLOGY/PRINCIPAL FINDINGS: Four of eight human neuroblastoma cell lines formed tumorspheres in neural stem cell media, and all contained some cells that expressed neurogenic stem cell markers including CD133, ABCG2, and nestin. Three lines tested could be induced into multi-lineage differentiation. LA-N-5 spheres were further studied and showed a verapamil-sensitive side population, relative resistance to doxorubicin, and CD133+ cells showed increased sphere formation and tumorigenicity. Oncolytic viruses, engineered to be clinically safe by genetic mutation, are emerging as next generation anticancer therapeutics. Because oncolytic viruses circumvent typical drug-resistance mechanisms, they may represent an effective therapy for chemotherapy-resistant tumor initiating cells. A Nestin-targeted oncolytic herpes simplex virus efficiently replicated within and killed neuroblastoma tumor initiating cells preventing their ability to form tumors in athymic nude mice. CONCLUSIONS/SIGNIFICANCE: These results suggest that human neuroblastoma contains tumor initiating cells that may be effectively targeted by an oncolytic virus.

Examples of news items about this publication:

Targeting Cancer's Own Stem Cells to Fight Recurrence, Forbes, January 21, 2009. First paragraph:

Scientists have located a group of cancer stem cells or "tumor-initiating cells" which, when targeted with a reprogrammed herpes virus, are prevented from turning malignant.

Engineered Virus Targets And Kills Apparent Cancer Stem Cells In Neuroblastoma, ScienceDaily, January 21, 2009. First paragraph:

After identifying an apparent population of cancer stem cells for neuroblastoma, researchers successfully used a reprogrammed herpes virus to block tumor formation in mice by targeting and killing the cells.

Virus made to kill cancer stem cells, UPI, January 22, 2009. First paragraph:

U.S. scientists say they have engineered a virus to target and kill apparent cancer stem cells involved in neuroblastoma tumors.

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.

ErbB2 induces Notch1 activity and function in breast cancer cells

ErbB2 induces Notch1 activity and function in breast cancer cells by Jaime Lindsay and 18 co-authors, including Richard G Pestell, Clinical and Translational Science 2008(Sep 10); 2(1): 107-115. Abstract:

The ErbB2 (Her2/neu epidermal growth receptor family) oncogene is overexpressed in 30% to 40% of human breast cancers. Cyclin D1 is the regulatory subunit of the holoenzyme that phosphorylates and inactivates the retinoblastoma (pRb) tumor suppressor and is an essential downstream target of ErbB2-induced tumor growth. Herein, we demonstrate that ErbB2 induces the activity of the Notch signaling pathway. ErbB2 induction of DNA synthesis, contact-independent growth, and mammosphere induction required Notch1. ErbB2-induced cyclin D1 and cyclin D1 expression was suficient to induce Notch1 activity, and conversely, genetic deletion of Notch1 in mammary epithelial cells using foxed Notch (Notch^fl/fl) mice demonstrated that cyclin D1 is induced by Notch1. Genetic deletion of cyclin D1 or small interfering RNA (siRNA) to cyclin D1-reduced Notch1 activity and reintroduction of cyclin D1 into cyclin D1-deficient cells restored Notch1 activity through the inhibition of Numb, an endogenous inhibitor of Notch1 activity. Thus, cyclin D1 functions downstream as a genetic target of Notch1, amplifies Notch1 activity by repressing Numb, and identifies a novel pathway by which ErbB2 induces Notch1 activity via the induction of cyclin D1.

At present, the full text of this article is freely accessible.

For examples of news items about this article, see: Breast Cancer - Targeting A Protein Called Cyclin D1 May Block The Expansion Of Cancerous Stem Cells, Medical News Today, November 6, 2008, and, Therapy may block expansion of breast cancer cells, Science Centric, November 6, 2008.

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.