Novel approach to target cancer stem cells for therapy

Novel approach to target cancer stem cells for therapy

Medical Hypotheses xxx (2015) xxx–xxx Contents lists available at ScienceDirect Medical Hypotheses journal homepage: N...

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Medical Hypotheses xxx (2015) xxx–xxx

Contents lists available at ScienceDirect

Medical Hypotheses journal homepage:

Novel approach to target cancer stem cells for therapy Ajumeera Rajanna ⇑ Stem Cell Research/Department of Biochemistry, National Institute of Nutrition, Hyderabad 500007, India

a r t i c l e

i n f o

Article history: Received 6 April 2015 Accepted 9 November 2015 Available online xxxx

a b s t r a c t Even though lots of efforts have been made to find different strategies for cancer treatments, currently available therapeutic approaches are chemotherapy, radiation and surgery or combination of these. These treatments prolonged the survival of patients but did not assure complete cure of the disease. Recent scientific evidences suggest that cancer stem cells (CSC) are responsible for recurrence, resistance and existence of this disease even after various therapeutic treatments. Therefore, we hypothesize that the best approach is to target CSCs along with cancer cells for complete remission of the disease. Before targeting these cells, studying their morphological, proliferation, behavioral aspects, physicochemical interaction and characterizations are very important. For therapeutic approach the differentiation capacity of these cells to cancer cells with or without drugs is critical. To study basic parameters; the best approach would be aseptic sorting of CSCs from cancer cells based on specific cell surface markers by flowcytometer or magnetic cell sorter. The sorted cells have to be grown in culture conditions and treat with optimum concentrations of drugs to target CSC and cancer cell to find appropriate potential combination. Ó 2015 Elsevier Ltd. All rights reserved.

Introduction The world cancer report 2014 has confirmed that 80% of all cancer deaths occurred in less developed regions of the world. Developing countries also witnessing a rise in cancer deaths due to unhealthy life style and less physical exercise which includes increased consumption of alcohol and smoking [1]. Even though, chemotherapy improved the quality and longevity of life of cancer patients, complete remission of disease is not achieved yet. Current scientific evidence strongly suggests that cancer stem cells (CSC) are responsible for recurrence of the disease even after chemotherapy [2]. CSCs are defined as a population of tumor-initiating cells present in tumors and they undergo self-renewal and differentiation by which CSCs generate diverse cells that form tumors [3,4]. CSCs were identified and isolated from different types of tumors like breast [5], pancreatic [6], prostate [7], medullary thyroid [8], lung [9], colon [10], ovarian [11], brain [12] and melanoma [13] and others. These cells may initiate cancer, metastasis, progression, drug resistance, recurrence and malignancies [14]. Therefore, it is crucial to focus more on cancer stem cells morphology, behavioral aspects and characterization of cells. Most attractive strategy to study properties of CSCs is to isolate them aseptically and study all properties in detail. Furthermore, evaluating the efficiency of some chemotherapeutic agents will also provide insights in to the ⇑ Tel.: +91 40 27197245; fax: +91 40 27019074. E-mail address: [email protected]

pathophysiology of the disease. Data obtained from this study may also be useful for screening potential anticancer drugs in the future. Hypothesis Current treatment strategies for cancer include chemotherapy, surgery and radiation or combination of these. Chemotherapy has been the most popular strategy due to simplicity of administering the drugs. However, prolong usage of chemotherapeutic drugs lead to dose dependent side effects and drug resistance. Surgical removal of tumor is not only limited for solid tumors but also is highly expensive. Radiation therapy, even though useful in treatment after surgical removal, draw backs such as damage of healthy cells surrounding cancers cells is a major problem. However, the considerable improvement has been observed in initial stages of treatment. Recent scientific evidence suggests that CSCs are real culprit of the disease. Therefore, we hypothesize (Fig. 1) that a combination strategy that involves treatment of both normal cancer and CSCs could be a better alternative for successful treatment of the disease. Testing the hypothesis The first-step is to understand the ability of CSCs regenerative and differentiate capacity to transform into cancer cells. Several research laboratories have made considerable progress in 0306-9877/Ó 2015 Elsevier Ltd. All rights reserved.

Please cite this article in press as: Rajanna A. Novel approach to target cancer stem cells for therapy. Med Hypotheses (2015), mehy.2015.11.009


A. Rajanna / Medical Hypotheses xxx (2015) xxx–xxx

An Cancer Drug

Cancer cell

Differenaon & Self renewal

Experimental design

Tumor CSC

An CSCs Drug Proliferaon

Tumor Combinaon



+ ) No Tumor

Fig. 1. Combination of anti cancer and anti CSC drugs is better approach to target and restrict cancer disease progression.

understanding the CSCs and their uniqueness compared with tumor cells in their metastasis property [15]. Overwhelming evidence supports the vital role of this side population (SP) in initiation and maintenance of tumor in addition to their capability to dictate invasion, metastasis, heterogeneity, and multi-drug resistance (MDR). Identification and isolation of these CSCs using putative surface markers have been a priority of research in cancer [16]. These CSCs cells have been identified and isolated from different types of tumors based on specific markers available in the market. To validate from primary or immortalized cell lines different cancer tissues have specific signatures such as: Pancreatic CD133+, CD44+, CD24+, EpCAM+ [17,18], brain cancer (CD133, SSEA1, BCRP1, A2B5) [19], Leukemia (CD34+, CD38 , CD7, 1HLA, DR, CD90, CD123, CD117) [20], Colon cancer CD133+, CD44+, CD166+, EpCAM, CD24+ [3,21,10], Lung cancer CD133+, ABCG2high [20,22], Liver cancer CD133+, CD90+, CD49f+ [23,24], Breast cancer CD44+, CD24 , ESA+, ALDH-1high [25,26], Prostate cancer CD133+, CD44+, a2b1high [27], Multiple myeloma CD138 [28,29], Melanoma CD20+ [13], Head and neck cancer CD44+ [30]. The validation of new drugs has to pass many drug development approval processes that could cost money and time before they could be available for treatment. The alternative approach for chemotherapy is to search potential old drugs for new anticancer activity. In this direction recently; the anti-diabetic drug metformin has gained attention for its potential anticancer effects [31–34]. An in vitro and in vivo study showed that metformin can eliminate CSCs and virtually eradicates breast tumors in mice when given along with doxorubicin [35]. The first report defining metformin’s specific action against stem cells was published and demonstrated that breast cancer stem cells, characterized by CD44high CD24low phenotype, are susceptible to metformin at low doses that do not affect the tumor cells [36]. Another drug thioridazine routinely prescribed for antipsychotic drug gained attention towards anti cancer activity by targeting cancer stem cells and changing them in to non cancerous cells via dopamine receptor on the surface of the cancer cells in both leukemia and breast cancer patients [37,38]. In addition drugs like salinomycine [39], parthenolide [20], curcumin [40], tranilast [41] were also used against cancer stem cell growth and inhibition. The present hypothesis emphasizes on targeting CSC along with cancer cells. The present drugs used to treat cancer cells cannot reduce the proliferation of CSCs and therefore will result in differentiation and self-renewal of CSCs to tumor cells. Therefore, a combination strategy that restricts growth of both CSCs and cancer cells simultaneously could be an attractive approach for successful treatment of the disease (Fig. 1). Furthermore, it is crucial to know the details of properties of CSC such as morphology, characterization, differentiation capacities etc. as it will help us in designing newer strategies in the treatment of cancer.

Experiments could be designed taking different cancer cell lines. Generally cancer cells grown in DMEM or RPMI mediums supplemented with 10% FBS and 1% penicillin/streptomycin maintained at 37 °C with 5% CO2. The IC50 concentrations of CSC targeted drugs are used for experiments. Each experiment will be repeated 3 times and average will be represented as final reading. Most of experiments like cells sorting, cell cycle, and apoptosis using fluorescence dyes will be analyzed by flowcytometer. Equal cell number (10,000 cells) will be passed through the flow cytometer for each experiment. Based on CSC specific markers expressions the labeled cells will be aseptically sorted and were grown in CO2 incubator. To compare the differentiation and multiplication capacity of CSCs and non-CSCs cells the cell cycle analysis and RT PCR would be performed. These results may be substantiated by measuring protein levels using western blot experiments and reconfirmed by protein expression with the help of flowcytometer. Concluding remarks This hypothesis for this study may throw light on importance to target CSCs with combination of anticancer drugs to design newer strategies in cancer therapy which may result incomplete remission in cancer cells growth. This strategy in cancer therapeutics could be useful to update the knowledge and transition from bench to bedside for better cancer therapy. Funding The author acknowledges National Institute of Nutrition (NIN), Hyderabad, Indian Council of Medical Research (ICMR) and Department of Biotechnology (DBT), New Delhi for the support of grants. Conflict of interest There is no conflict of interest with this hypothesis. References [1] Stewart Bernard W, Wild Christopher P, editors. World Cancer Report 2014. International Agency for Research on Cancer; 2014. [2] Thomas D, Christa N, Sarah S, et al. Recurrence cancer stem cells – made by cell fusion? Med Hypotheses 2009;73(4):542–7. [3] Dalerba P, Dylla SJ, Park IK, et al. Phenotypic characterization of human colorectal cancer stem cells. Proc Natl Acad Sci USA 2007;104:10158–63. [4] Clevers H. The cancer stem cell: premises, promises and challenges. Nat Med 2011;17:313–9. [5] Zhuang Y, Miskimins WK. Metformin induces both caspase-dependent and poly (ADP-ibose) polymerase-dependent cell death in breast cancer cells. Mol Cancer Res 2011;9(5):603–15. [6] Bao B, Wang Z, Ali S, et al. Metformin inhibits cell proliferation, migration and invasion by attenuating CSC function mediated by deregulating miRNAs in pancreatic cancer cells. Cancer Prev Res 2012;5(3):355–64. [7] Ben SI, Laurent K, Loubat A, et al. The antidiabetic drug metformin exerts an anti tumoral effect in vitro and in vivo through a decrease of cyclin D1 level. Oncogene 2008;27(25):3576–86. [8] Klubo GJ, Jensen K, Costello J, et al. Metformin inhibits growth and decreases resistance to anoikis in medullary thyroid cancer cells. Endocr Relat Cancer 2012;19(3):447–56. [9] Kim CF, Jackson EL, Woolfenden AE, et al. Identification of bronchioalveolar stem cells in normal lung and lung cancer. Cell 2005;121:823–35. [10] O’Brien CA, Pollett A, Gallinger S, et al. A human colon cancer cell capable of initiating tumour growth in immunodeficient mice. Nature 2007;445:106–10. [11] Szotek PP, Pieretti VR, Masiakos PT, et al. Ovarian cancer side population defines cells with stem cell-like characteristics and Mullerian Inhibiting Substance responsiveness. Proc Natl Acad Sci USA 2006;103:11154–9. [12] Piccirillo SGM, Reynolds BA, Zanetti N, et al. Bone morphogenetic proteins inhibit the tumorigenic potential of human brain tumour-initiating cells. Nature 2006;444:761–5. [13] Fang D, Nguyen TK, Leishear K, et al. A tumorigenic subpopulation with stem cell properties in melanomas. Cancer Res 2005;65(20):9328–37.

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Please cite this article in press as: Rajanna A. Novel approach to target cancer stem cells for therapy. Med Hypotheses (2015), mehy.2015.11.009