Insights into the stem cells of CML

Insights into the stem cells of chronic myeloid leukemia by I Sloma, X Jiang, A C Eaves and C J Eaves, Leukemia 2010(Sep 23). [Epub ahead of print][PubMed citation]. Abstract:

Chronic myeloid leukemia (CML) has long served as a paradigm for generating new insights into the cellular origin, pathogenesis and improved approaches to treating many types of human cancer. Early studies of the cellular phenotypes and genotypes represented in leukemic populations obtained from CML patients established the concept of an evolving clonal disorder originating in and initially sustained by a rare, multipotent, self-maintaining hematopoietic stem cell (HSC). More recent investigations continue to support this model, while also revealing new insights into the cellular and molecular mechanisms that explain how knowledge of CML stem cells and their early differentiating progeny can predict the differing and variable features of chronic phase and blast crisis. In particular, these emphasize the need for new agents that effectively and specifically target CML stem cells to produce non-toxic, but curative therapies that do not require lifelong treatments.

Critical molecular pathways in CSCs of CML

Critical molecular pathways in cancer stem cells of chronic myeloid leukemia by Y Chen, C Peng, C Sullivan, D Li and S Li, Leukemia 2010(Sep); 24(9): 1545-54. Epub 2010 Jun 24. [Connotea bookmark][PubMed citation][Full text]. The abstract of this OA review:

Inhibition of BCR-ABL with kinase inhibitors in the treatment of Philadelphia-positive (Ph(+)) chronic myeloid leukemia (CML) is highly effective in controlling but not curing the disease. This is largely due to the inability of these kinase inhibitors to kill leukemia stem cells (LSCs) responsible for disease relapse. This stem cell resistance is not associated with the BCR-ABL kinase domain mutations resistant to kinase inhibitors. Development of curative therapies for CML requires the identification of crucial molecular pathways responsible for the survival and self-renewal of LSCs. In this review, we will discuss our current understanding of these crucial molecular pathways in LSCs and the available therapeutic strategies for targeting these stem cells in CML.

Must the last CML cell be killed?

Do we have to kill the last CML cell? DM Ross, TP Hughes and JV Melo, Leukemia 2010(Sep 16) [Epub ahead of print][FriendFeed entry][PubMed citation][Full text]. The abstract of this OA review:

Previous experience in the treatment of chronic myeloid leukaemic (CML) has shown that the achievement of clinical, morphological and cytogenetic remission does not indicate eradication of the disease. A complete molecular response (CMR; no detectable BCR-ABL mRNA) represents a deeper level of response, but even CMR is not a guarantee of elimination of the leukaemic, because the significance of CMR is determined by the detection limit of the assay that is used. Two studies of imatinib cessation in CMR are underway, cumulatively involving over 100 patients. The current estimated rate of stable CMR after stopping imatinib is approximately 40%, but the duration of follow-up is relatively short. The factors that determine relapse risk are yet to be identified. The intrinsic capacity of any residual leukaemic cells to proliferate following the withdrawal of treatment may be important, but there may also be a role for immunological suppression of the leukaemic clone. No currently available test can formally prove that the leukaemic clone is eradicated. Here we discuss the sensitive measurement of minimal residual disease, and speculate on the biology of BCR-ABL-positive cells that may persist after effective therapy of CML.

Partnership Pays Off

Northern Exposure by Emmet Pierce, San Diego Business Journal, August 16, 2010. Excerpt:

An example of San Diegans collaborating with Canadians is the work that has taken place at the UC San Diego Moores Cancer Center in cooperation with research at the University of Toronto. The partnership has enabled San Diego researchers to acquire a $20 million grant to develop drugs to be used against leukemia stem cells, Barr says.Dr. Catriona Jamieson, director of the stem cell research program at the Moores center, said scientists from Toronto and San Diego share "a deep and abiding interest in cancer stem cell biology." The Canadian consulate in San Diego was instrumental in helping to create a relationship in which both institutions would benefit, sharing information and applying for funds to support their research.

"The idea was to establish a Canada-California cancer stem cell initiative and obtain connections with Canadian funding agencies, particularly Genome Canada and the Ministry of Health," she said.

Jamieson added, "The most important thing is it allows people with disparate abilities and backgrounds to work together on the same problem."

Barr said the University of Toronto also was able to secure a $20 million research grant because of the collaboration, "so the team is greater than the sum of its parts."

CSC news links 2010-04-18

For links to recent news items, visit these [Twitter] or [FriendFeed] pages. Examples of a few news items that have received attention:

• Split ends in CML: divergent roles of Hes1 by Catriona Jamieson, Blood 2010(Apr 8); 115(14): 2726-7 [FriendFeed entry][Connotea bookmark][PubMed citation][Full text PDF]. A comment on: Hes1 immortalizes committed progenitors and plays a role in blast crisis transition in chronic myelogenous leukemia by Fumio Nakahara and 13 co-authors, Blood 2010(Apr 8); 115(14): 2872-81. [Epub 2009(Oct 27)][PubMed citation].


• Metabolism and the leukemic stem cell by Omar Abdel-Wahab and Ross L Levine, J Exp Med 2010(Apr 12); 207(4): 677-80 [Epub 2010(Apr 5)][FriendFeed entry][ResearchGATE entry][CiteULike entry][Connotea bookmark][PubMed citation][Full text].


• A hypoxic niche regulates glioblastoma stem cells through hypoxia inducible factor 2alpha by Sascha Seidel and 13 co-authors, including Till Acker, Brain 2010(Apr); 133(Pt 4): 983-95 [FriendFeed entry][ResearchGATE entry][Connotea bookmark][PubMed citation].

Review about retroviral-induced leukemogenesis and the CSC hypothesis

Hematopoietic stem cells and retroviral infection by Prabal Banerjee, Lindsey Crawford, Elizabeth Samuelson and Gerold Feuer, Retrovirology 2010(Feb 4); 7(1): 8 [Epub ahead of print][Connotea bookmark][[FriendFeed entry][PubMed Citation][Full text (PDF)].

Includes sections on Leukemia Stem Cells/Cancer Stem Cells (LSC/CSC) and on The Cancer Stem Cell Hypothesis.

Molecular signatures of quiescent, mobilized and leukemia-initiating hematopoietic SC

Molecular Signatures of Quiescent, Mobilized and Leukemia-Initiating Hematopoietic Stem Cells by E Camilla Forsberg and 6 co-authors, including Irving L Weissman, PLoS One 2010(Jan 20);5(1):e8785. [Connotea bookmark][FriendFeed entry][Full text is publicly accessible (via Libre OA)]. PubMed Abstract:

Hematopoietic stem cells (HSC) are rare, multipotent cells capable of generating all specialized cells of the blood system. Appropriate regulation of HSC quiescence is thought to be crucial to maintain their lifelong function; however, the molecular pathways controlling stem cell quiescence remain poorly characterized. Likewise, the molecular events driving leukemogenesis remain elusive. In this study, we compare the gene expression profiles of steady-state bone marrow HSC to non-self-renewing multipotent progenitors; to HSC treated with mobilizing drugs that expand the HSC pool and induce egress from the marrow; and to leukemic HSC in a mouse model of chronic myelogenous leukemia. By intersecting the resulting lists of differentially regulated genes we identify a subset of molecules that are downregulated in all three circumstances, and thus may be particularly important for the maintenance and function of normal, quiescent HSC. These results identify potential key regulators of HSC and give insights into the clinically important processes of HSC mobilization for transplantation and leukemic development from cancer stem cells.

SC-derived gene expression profiles predict poor outcome for AML patients

Leukemic and Normal Stem Cell Transcriptional Signatures Determined by Functional Assays Are Predictive of the Overall Survival of AML Patients by Kolja Eppert and 11 co-authors, including John E Dick, Abstract #389, 51st ASH Annual Meeting, December 7, 2009. Final sentence:

Together these data support the hypothesis that the biological determinants that underlie stemness in both normal and leukemic cells are predictors of poor outcome, and are potential targets for novel therapy.

Targeting of AML-leukemic SC with monoclonal antibodies

Targeting of AML-leukemic stem cells with monoclonal antibodies by Erwin M Lee‌ and Richard B Lock, Future Oncol 2009(Nov); 5(9): 1327-30 [PubMed Citation][FriendFeed entry][Full text PDF]. Final sentence of the full text of this Editorial:

An AML patient surface immunophenotype is relatively cost-effective to characterize, raising the prospect of individualized therapy based on a selection of available MAbs. Most certainly, we are entering a new and exciting era in the struggle to improve outcome in adult AML.

Heterogeneity in the AML stem cell pool

Heterogeneity in the AML stem cell pool by Laura E Hays, Blood 2009(Nov 5); 114(19): 3976-7 [PubMed Citation][FriendFeed entry]. Excerpt:

To examine AML and stem cell diversity, Heuser and colleagues develop a novel murine model that closely mimics aggressive human AML and demonstrate an essential role of Stat5 in leukemic stem cell renewal.

Comment on: Modeling the functional heterogeneity of leukemia stem cells: role of STAT5 in leukemia stem cell self-renewal by Michael Heuser and 14 co-authors, including Gerald Krystal and R Keith Humphries, Blood 2009(Nov 5); 114(19): 3983-93 [Epub 2009(Aug 10)][PubMed Citation].

Leukemia SC cloak themselves to avoid detection

Leukemia cells evade immune system by mimicking normal cells, Stanford study shows by Krista Conger, News Release, Stanford University Medical Center, July 23, 2009. First sentence:

Human leukemia stem cells escape detection by co-opting a protective molecular badge used by normal blood stem cells to migrate safely within the body, according to a pair of studies by researchers at Stanford University Medical School.

See also: Molecule Helps Leukemia Cells Hide From Immune System, Drugs.com, July 23, 2009. First sentence:

Leukemia stem cells cleverly cloak themselves to avoid detection by a person's immune system, according to a pair of studies by researchers at Stanford University Medical School.

And: Leukemia cells evade immune system by mimicking normal cells, Stanford studies show, EurekAlert, July 23, 2009.

The two articles upon which the news releases are based:

1) CD47 Is Upregulated on Circulating Hematopoietic Stem Cells and Leukemia Cells to Avoid Phagocytosis by Siddhartha Jaiswal, Catriona H M Jamieson and 7 co-authors, including Irving L Weissman, Cell 2009(Jul 23); 138(2): 271-85. [PubMed Citation].

2) CD47 Is an Adverse Prognostic Factor and Therapeutic Antibody Target on Human Acute Myeloid Leukemia Stem Cells by Ravindra Majeti and 7 co-authors, including Irving L Weissman, Cell 2009(Jul 23); 138(2): 286-99. [PubMed Citation][FriendFeed entry].

Targeted therapy for AML stem cells

New Targeted Therapy Finds And Eliminates Deadly Leukemia Stem Cells, ScienceDaily July 3, 2009. [FriendFeed entry]. First paragraph:

New research describes a molecular tool that shows great promise as a therapeutic for human acute myeloid leukemia (AML), a notoriously treatment-resistant blood cancer. The study, published in the July 2nd issue of the journal Cell Stem Cell, describes exciting preclinical studies in which a new therapeutic approach selectively attacks human cancer cells grown in the lab and in animal models of leukemia.

The news release is about this article: Monoclonal antibody-mediated targeting of CD123, IL-3 receptor alpha chain, eliminates human acute myeloid leukemic stem cells by Liqing Jin and 14 co-authors, including John E Dick and Richard B Lock, Cell Stem Cell 2009(Jul 2); 5(1): 31-42. [PubMed Citation].

Alloreactive NK cells detect and target leukemic SCs

Human acute myeloid leukemia CD34+CD38– stem cells are susceptible to allorecognition and lysis by single KIR-expressing natural killer cells by Ulrich Langenkamp and 6 co-authors, including Aleksandra Wodnar-Filipowicz, Haematologica 2009(Jul 16) [Epub ahead of print][FriendFeed entry][Early version of the full text PDF]. PubMed Abstract:

The concept of tumor immunosurveillance has raised prospects for natural killer (NK) cell-based immunotherapy of human cancer. The cure of acute myeloid leukemia (AML) may depend on eradication of leukemic stem cells (LSCs), the self-renewing component of leukemia. Whether NK cells can recognize and lyse LSCs is not known. To develop strategies that effectively target AML-LSCs, we investigated anti-leukemic effects of human alloreactive single KIR(+) NK cells. NK effectors with KIR specificity mismatched with respect to HLA class I allotype of target cells effectively recognized AML-LSCs defined phenotypically as CD34(+)CD38(-), while healthy bone marrow-derived CD34(+)CD38(-) hematopoietic stem cells were spared, as demonstrated by cytotoxicity and hematopoietic colony-forming assays. The HDAC inhibitor valproic acid augmented the activating NKG2D ligand-dependent lysis of AML-CD34(+)CD38(-) LSCs. These results show that alloreactive NK cells have the potential to detect and target LSCs, and thus to improve the treatment outcome in AML.

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].

Therapeutic monoclonal antibody targeting of AML-LSCs

New Targeted Therapy Finds And Eliminates Deadly Leukemia Stem Cells, ScienceDaily July 3, 2009. [FriendFeed entry]. First two sentences:

New research describes a molecular tool that shows great promise as a therapeutic for human acute myeloid leukemia (AML), a notoriously treatment-resistant blood cancer. The study, published in the July 2nd issue of the journal Cell Stem Cell, describes exciting preclinical studies in which a new therapeutic approach selectively attacks human cancer cells grown in the lab and in animal models of leukemia.

This news release is about the article Monoclonal antibody-mediated targeting of CD123, IL-3 receptor alpha chain, eliminates human acute myeloid leukemic stem cells by Liqing Jin and 14 co-authors, including John E Dick and Richard B Lock, Cell Stem Cell 2009(Jul 2); 5(1): 31-42. PubMed Abstract:

Leukemia stem cells (LSCs) initiate and sustain the acute myeloid leukemia (AML) clonal hierarchy and possess biological properties rendering them resistant to conventional chemotherapy. The poor survival of AML patients raises expectations that LSC-targeted therapies might achieve durable remissions. We report that an anti-interleukin-3 (IL-3) receptor alpha chain (CD123)-neutralizing antibody (7G3) targeted AML-LSCs, impairing homing to bone marrow (BM) and activating innate immunity of nonobese diabetic/severe-combined immunodeficient (NOD/SCID) mice. 7G3 treatment profoundly reduced AML-LSC engraftment and improved mouse survival. Mice with pre-established disease showed reduced AML burden in the BM and periphery and impaired secondary transplantation upon treatment, establishing that AML-LSCs were directly targeted. 7G3 inhibited IL-3-mediated intracellular signaling of isolated AML CD34(+)CD38(-) cells in vitro and reduced their survival. These results provide clear validation for therapeutic monoclonal antibody (mAb) targeting of AML-LSCs and for translation of in vivo preclinical research findings toward a clinical application.

Specific target gene found using CML mouse model

Loss of the Alox5 gene impairs leukemia stem cells and prevents chronic myeloid leukemia by Yaoyu Chen, Yiguo Hu, Haojian Zhang, Cong Peng, Shaoguang Li, Nature Genetics 2009(June 7).

For a news release about this article, see: A lethal cancer knocked down by one-two drug punch, Genetic Engineering & Biotechnology News, June 7, 2009. Excerpts:

The researchers found that CML did not develop in mice without Alox5 because of impaired function of leukemia stem cells. Also, Alox5 deficiency did not affect normal stem cell function, providing the first clear differentiation between normal and cancer stem cells.

[Shaoguang] Li also treated mice with CML with Zileuton, an asthma medication that inhibits the Alox5 inflammation pathway, as well imatinib, commonly known as Gleevec, the most effective current leukemia medication. Imatinib effectively treated CML, but Zileuton was more effective. The two drugs combined provided an even better therapeutic effect.

[Thanks to Alexey Bersenov].

Transcriptional profiles of subsets within the CD34+ cell population in chronic phase CML

The hematopoietic stem cell in chronic phase CML is characterized by a transcriptional profile resembling normal myeloid progenitor cells and reflecting loss of quiescence by Ingmar Bruns and 16 co-authors, including Rainer Haas, Leukemia 2009(May); 23(5): 892-9 [Epub 2009(Jan 22)]. PubMed Abstract:

We found that composition of cell subsets within the CD34+ cell population is markedly altered in chronic phase (CP) chronic myeloid leukemia (CML). Specifically, proportions and absolute cell counts of common myeloid progenitors (CMP) and megakaryocyte-erythrocyte progenitors (MEP) are significantly greater in comparison to normal bone marrow whereas absolute numbers of hematopoietic stem cells (HSC) are equal. To understand the basis for this, we performed gene expression profiling (Affymetrix HU-133A 2.0) of the distinct CD34+ cell subsets from six patients with CP CML and five healthy donors. Euclidean distance analysis revealed a remarkable transcriptional similarity between the CML patients' HSC and normal progenitors, especially CMP. CP CML HSC were transcriptionally more similar to their progeny than normal HSC to theirs, suggesting a more mature phenotype. Hence, the greatest differences between CP CML patients and normal donors were apparent in HSC including downregulation of genes encoding adhesion molecules, transcription factors, regulators of stem-cell fate and inhibitors of cell proliferation in CP CML. Impaired adhesive and migratory capacities were functionally corroborated by fibronectin detachment analysis and transwell assays, respectively. Based on our findings we propose a loss of quiescence of the CML HSC on detachment from the niche leading to expansion of myeloid progenitors.

[Thanks to Alexey Bersenev].

Leukemic stem cells in blast crisis CML

The CML stem cell: evolution of the progenitor by Scott A Stuart, Yosuke Minami and Jean YJ Wang, Cell Cycle 2009(May 1); 8(9): 1338-43 [Epub 2009 May 17][PubMed Citation][Full text PDF (Gratis OA)].

Last paragraph of the section of full text entitled CML Stem Cells and CML Therapy:

While the differences between CSCs and cells of the bulk tumor may prevent CSCs from being eliminated by therapies that target the bulk tumor, these differences may also provide unique therapeutic targets. Therefore, the identification of cancer stem cells may open the door to new targeted therapies as the differences between the cancer stem cell, the bulk tumor, and normal cells are realized. The observation that the leukemic GMPs in CML blast crisis largely depend on the β-catenin pathway for self-renewal point to this pathway as one attractive therapeutic target. Future studies with purified populations of HSCs and GMPs from patients with CML will be essential to identifying additional differences amenable to therapeutic intervention.

[CSCs = cancer stem cells; CML = chronic myeloid leukemia; HSCs = hematopoietic stem cells; GMPs = granulocyte-macrophage progenitors].

Found via Twitter. (Thanks to Alexey Bersenev).

Inhibitory effects of omacetaxine on leukemic stem cells

Inhibitory effects of omacetaxine on leukemic stem cells and BCR-ABL-induced chronic myeloid leukemia and acute lymphoblastic leukemia in mice, by Yaoyu Chen and 5 co-authors, including Shaoguang Li, Leukemia 2009(Mar 26) [Epub ahead of print][PubMed Citation]. Examples of related news items:

Data suggesting that omacetaxine can eradicate leukemic stem cells may offer a breakthrough for CML, Physorg.com, March 26, 2009. Excerpt:

Data showing the ability of omacetaxine to kill leukemic stem cells in mouse models with drug-resistant chronic myelogenous leukemia (CML) are the subject of an advance online publication in the journal Leukemia, ChemGenex Pharmaceuticals Limited (ASX:CXS and NASDAQ:CXSP) announced today. The findings of this study provide new insights into the problem of minimal residual disease and may open the door to the development of a curative treatment strategy for some patients with CML. .....

Leukemic stem cell killer ‘omacetaxine’ help rises Chemgenex’s share, Stem Cell Research Blog, March 28, 2009. Excerpt:

ChemGenex Pharmaceuticals announced on March 26th, 2009 through online publication in the journal Leukemia, about the ability of omacetaxine to kill leukemic stem cells in mouse models with drug-resistant chronic myelogenous leukemia (CML). .....

About AML and CML

1) First Genome-Wide Expression Analysis Yields Better Understanding of Leukemia, News Release, University of Rochester Medical Center, February 10, 2009.

Genome-wide leukemia analysis completed, UPI Science News, February 11, 2009.

These news items are about the article: Dysregulated gene expression networks in human acute myelogenous leukemia stem cells by Ravindra Majeti and 9 co-authors, including Michael W Becker, Leroy Hood, Michael F Clarke and Irving L Weissman, Proc Natl Acad Sci USA 2009(Feb 13) [Epub ahead of print][PubMed Citation][Version in PMC].

2) Scientists Uncover indicator that Warns leukemia is Progressing to more dangerous form by Steve Benowitz, News Release, UC San Diego News Center, February 17, 2009.

This news release is about the article: Glycogen synthase kinase 3{beta} missplicing contributes to leukemia stem cell generation by Annelie E Abrahamsson and 15 co-authors, including Armand Keating, Robert S Negrin, Irving L Weissman and Catriona H M Jamieson, Proc Natl Acad Sci USA 2009(Feb 23) [Epub ahead of print][PubMed Citation][Full text PDF].