Cancer Stem Cells: Current Challenges and Future Perspectives.

Despite major advances in health care including improved diagnostic tools, robust chemotherapeutic regimens, advent of precision, adjuvant and multimodal therapies, there is a major proportion of patients that still go on to experience tumor progression and recurrence. Cancer stem cells (CSCs) are shown to be responsible for tumor persistence and relapse. This subpopulation of cancer cells possess normal stem cell like traits of self-renewal, proliferation, and multilineage differentiation. Currently, they are isolated and enriched based on the cell surface markers that can be detected and sorted through fluorescence and magnetic-based cell sorting. In this chapter, we review the current challenges and limitations often encountered in CSC research, including the identification of universal markers, therapy resistance, and new drug development. Current and future perspectives are discussed to address these challenges including utilization of cutting-edge technologies such as next-generation sequencing to elucidate the genome, epigenome, and transcriptome on a single-cell level and genome-wide CRISPR-Cas9 screens to identify novel pathway-based targeted therapies. Further, we discuss the future of precision medicine and the need for the improvement of clinical trial designs.

Cancer-selective metabolic vulnerabilities in MYC-amplified medulloblastoma.

MYC-driven medulloblastoma (MB) is an aggressive pediatric brain tumor characterized by therapy resistance and disease recurrence. Here, we integrated data from unbiased genetic screening and metabolomic profiling to identify multiple cancer-selective metabolic vulnerabilities in MYC-driven MB tumor cells, which are amenable to therapeutic targeting. Among these targets, dihydroorotate dehydrogenase (DHODH), an enzyme that catalyzes de novo pyrimidine biosynthesis, emerged as a favorable candidate for therapeutic targeting. Mechanistically, DHODH inhibition acts on target, leading to uridine metabolite scarcity and hyperlipidemia, accompanied by reduced protein O-GlcNAcylation and c-Myc degradation. Pyrimidine starvation evokes a metabolic stress response that leads to cell-cycle arrest and apoptosis. We further show that an orally available small-molecule DHODH inhibitor demonstrates potent mono-therapeutic efficacy against patient-derived MB xenografts in vivo. The reprogramming of pyrimidine metabolism in MYC-driven medulloblastoma represents an unappreciated therapeutic strategy and a potential new class of treatments with stronger cancer selectivity and fewer neurotoxic sequelae.

Dual Antigen T Cell Engagers Targeting CA9 as an Effective Immunotherapeutic Modality for Targeting CA9 in Solid Tumors.

Glioblastomas (GBM), the most common malignant primary adult brain tumors, are uniformly lethal and are in need of improved therapeutic modalities. GBM contain extensive regions of hypoxia and are enriched in therapy resistant brain tumor-initiating cells (BTICs). Carbonic anhydrase 9 (CA9) is a hypoxia-induced cell surface enzyme that plays an important role in maintenance of stem cell survival and therapeutic resistance. Here we demonstrate that CA9 is highly expressed in patient-derived BTICs. CA9+ GBM BTICs showed increased self-renewal and proliferative capacity. To target CA9, we developed dual antigen T cell engagers (DATEs) that were exquisitely specific for CA9-positive patient-derived clear cell Renal Cell Carcinoma (ccRCC) and GBM cells. Combined treatment of either ccRCC or GBM cells with the CA9 DATE and T cells resulted in T cell activation, increased release of pro-inflammatory cytokines and enhanced cytotoxicity in a CA9-dependent manner. Treatment of ccRCC and GBM patient-derived xenografts markedly reduced tumor burden and extended survival. These data suggest that the CA9 DATE could provide a novel therapeutic strategy for patients with solid tumors expressing CA9 to overcome treatment resistance. .

Formulation and optimization of doxorubicin loaded polymeric nanoparticles using Box-Behnken design: ex-vivo stability and in-vitro activity.

Biodegradable nanoparticles (NPs) have gained tremendous interest for targeting chemotherapeutic drugs to the tumor environment. Inspite of several advances sufficient encapsulation along with the controlled release and desired size range have remained as considerable challenges. Hence, the present study examines the formulation optimization of doxorubicin loaded PLGA NPs (DOX-PLGA-NPs), prepared by single emulsion method for cancer targeting. Critical process parameters (CPP) were selected by initial screening. Later, Box-Behnken design (BBD) was used for analyzing the effect of the selected CPP on critical quality attributes (CQA) and to generate a design space. The optimized formulation was stabilized by lyophilization and was used for in-vitro drug release and in-vitro activity on A549 cell line. Moreover, colloidal stability of the NPs in the biological milieu was assessed. Amount of PLGA and PVA, oil:water ratio and sonication time were the selected independent factors for BBD. The statistical data showed that a quadratic model was fitted to the data obtained. Additionally, the lack of fit values for the models was not significant. The delivery system showed sustained release behavior over a period of 120h and was governed by Fickian diffusion. The multipoint analysis at 24, 48 and 72h showed gradual reduction in IC50 value of DOX-PLGA-NPs (p<0.05, Fig. 9). DOX-PLGA-NPs were found to be stable in the biological fluids indicating their in-vivo applicability. In conclusion, optimization of the DOX-PLGA-NPs by BBD yielded in a promising drug carrier for doxorubicin that could provide a novel treatment modality for cancer.

CD90 a potential cancer stem cell marker and a therapeutic target.

Cancer Stem Cells (CSCs) have been recently identified and their role in carcinogenesis has been ascertained. CSCs have been correlated with high relapse in certain cancers, multiple drug resistance against chemotherapy and metastasis. Several markers such as CD133, CD24, CD44, EpCAM, and CD26 have been identified to isolate and characterize CSCs. None of these markers or their combinations are universal in nature and can be used to isolate CSCs from all types of cancer. CD90 is one such marker whose expression has been extensively studied in recent years. CD90+ cells have been isolated from several types of tumors and shown to exhibit cardinal properties of CSCs such as proliferation, differentiation, spheroid formation, metastasis and ability to form tumor xenograft in immunodeficient mice. It is also found to be co-expressed with several other CSC markers. CD90 is therefore, suggested as a candidate marker as well as a potential therapeutic target for elimination of CSCs.

Abortifacient potential of methanolic extract of Anthocephalus cadamba stem bark in mice.

ETHNOPHARMACOLOGICAL RELEVANCE: Medicinal plants possessing abortifacient activity have been used traditionally for a long time in folk medicine. Anthocephalus cadamba, is one such herb that has been known to possess abortifacient potential in ethnobotanical literature, but has not been validated scientifically. MATERIALS AND METHODS: The methanolic extract of Anthocephalus cadamba stem bark (MEAC) was prepared and tested for abortifacient, estrogenic and uterotrophic activity. Pregnant Swiss albino mice were randomized into 5 groups (1-5). Group 1 (negative control) received 0.2% w/v agar, group 2-4 (received extract at the dose of 500, 1000 and 1500mg/kg b.w.) and group 5 received mifepristone at a dose of 5.86mg/kg b.w. respectively, by oral route from 10(th) to 18(th) day post-coitum daily, and various parameters recorded. The uterotrophic bioassay was performed in bilaterally ovariectomized mice dosed from 9(th) to 15(th) day of ovariectomy and change in uterotrophic parameters was observed. RESULTS: Preliminary phytochemical screening revealed presence of glycosides, alkaloids, steroids, saponins, triterpenoids, flavonoids and tannins. No signs of clinical toxicity were observed at any time during the period of treatment. The extract significantly reduced (P<0.05) the number of live fetus, weight and survival ratio of the fetus, number of corpora lutea, progesterone, estradiol and luteinizing hormone whereas the number of dead fetus, number of mice that aborted, percentage vaginal opening and post-implantation loss increased significantly (P<0.05). The estrogenicity experiments showed increase in uterine weight (P<0.05), ballooning of uterus, uterine glucose (P<0.05) and ALP (P<0.001) in extract treated group dose dependently. In addition, the extract also induced vaginal bleeding preceding parturition. CONCLUSION: This study has substantiated the abortifacient potential of the methanolic extract of Anthocephalus cadamba stem bark. The activity was more marked in 1000 and 1500mg/kg b.w. of the extract and was comparable to that of mifepristone. The mechanism of abortion could possibly be through changes in the uterine mileu, altered hormone levels, luteolysis and partly, estrogenicity. This study thus justifies the ethnobotanical claim of MEAC as an abortifacient.

An improved and versatile immunosuppression protocol for the development of tumor xenograft in mice.

BACKGROUND: The objective of the present study was to evaluate the efficacy of a simple, versatile and cost-effective immunosuppression protocol, using cyclosporine, ketoconazole and cyclophosphamide drug regimen to develop human tumor xenograft in mice. MATERIALS AND METHODS: Cyclosporine, ketoconazole and cyclophosphamide drug regimen was administered to C57BL/6 mice to induce immunosuppression. Five million A549, LNCaP and KB cells were injected subcutaneously in the immunocompromised mice for the development of tumor xenograft. Tumor volume was calculated every week. Histopathology of tumor tissue was analyzed. RESULTS: Prolong immunosuppression was achieved by this combination treatment. The average tumor volume was found to be greater than 600 mm(3). Histopathology of tumor tissue revealed the presence of large and irregular nucleus and scanty cytoplasm, which are characteristic of malignant cells. CONCLUSION: A versatile immunosuppression protocol was developed which was validated for xenograft development using three different cell lines, with a 100% take rate and no mortality.