Pharmacogenomics and cancer stem cells: a changing landscape?

Decursinol Angelate Inhibits Glutamate Dehydrogenase 1 Activity and Induces Intrinsic Apoptosis in MDR-CRC Cells

Colorectal cancer (CRC) was the second most commonly diagnosed cancer worldwide and the second most common cause of cancer-related deaths in Europe in 2020. After CRC patients' recovery, in many cases a patient's tumor returns and develops chemoresistance, which has remained a major challenge worldwide. We previously published our novel findings on the role of DA in inhibiting the activity of GDH1 using in silico and enzymatic assays. No studies have been conducted so far to explain the inhibitory role of DA against glutamate dehydrogenase in MDR-CRC cells. We developed a multidrug-resistant colorectal cancer cell line, HCT-116^MDR, after treatment with cisplatin and 5-fluorouracil. We confirmed the MDR phenotype by evaluating the expression of MDR1, ABCB5, extracellular vesicles, polyploidy, DNA damage response markers and GDH1 in comparison with parental HCT-116^WT (HCT-116 wild type). Following confirmation, we determined the IC₅₀ and performed clonogenic assay for the efficacy of decursinol angelate (DA) against HCT-116^MDR (HCT-116 multidrug resistant). Subsequently, we evaluated the novel interactions of DA with GDH1 and the expression of important markers regulating redox homeostasis and cell death. DA treatment markedly downregulated the expression of GDH1 at 50 and 75 μM after 36 h, which directly correlated with reduced expression of the Krebs cycle metabolites α-ketoglutarate and fumarate. We also observed a systematic dose-dependent downregulation of MDR1, ABCB5, TERT, ERCC1 and γH2AX. Similarly, the expression of important antioxidant markers was also downregulated. The markers for intrinsic apoptosis were notably upregulated in a dose-dependent manner. The results were further validated by flow cytometry and TUNEL assay. Additionally, GDH1 knockdown on both HCT-116^WT and HCT-116^MDR corresponded to a decreased expression of γH2AX, catalase, SOD1 and Gpx-1, and an eventual increase in apoptosis markers. In conclusion, inhibition of GDH1 increased ROS production, decreased cell proliferation and increased cell death.

Exploiting fourier transform infrared and Raman microspectroscopies on cancer stem cells from oral squamous cells carcinoma: new evidence of acquired cisplatin chemoresistance

Oral Squamous Cells Carcinoma (OSCC) is characterised by the risk of recurrence and the onset of a refractoriness response to chemotherapy drugs. These phenomena have been recently related to a subpopulation of Cancer Stem Cells (CSCs), which have either an innate or acquired drug resistance, triggered by chemotherapy treatments. In this light, to precisely target chemotherapy regimens, it is essential to improve knowledge on CSCs, with a particular focus on their molecular features. In this work, a subpopulation of CSCs, isolated by tumour sphere formation from primary OSCC cells, were treated with cisplatin for 16, 24 and 48 hours and analysed by infrared absorption and Raman microspectroscopies. CSC spectral data were compared with those obtained in previous work, for primary OSCC cells treated under the same conditions. Routine viability/apoptosis cell-based assays evidenced in CSCs and primary OSCCs, a similar degree of sensitivity to the drug at 24 hours, while a reversion of the conventional monotonic time response exhibited by OSCCs was shown by CSCs at 48 hours. This peculiar time response was also supported by the analysis of IR and Raman data, which pinpointed alterations in the lipid composition and DNA conformation in CSCs. The results obtained suggest that CSCs, although sharing with OSCC cells a similar sensitivity to cisplatin, display the onset of a mechanism of chemoresistance and enrichment of resistant CSCs as a result of drug treatment, shedding new light on the severe issue of refractoriness of some patients to chemotherapy conventionally used for OSCC.

LDH-doped electrospun short fibers enable dual drug loading and multistage release for chemotherapy of drug-resistant cancer cells

LDH-incorporated PLGA short nanofibers can be loaded with dual drugs for multistage release and chemotherapy of drug-resistant cancer cells.

Mechanisms of cancer stem cell therapy

Cancer stem cells (CSCs) are responsible for carcinogenesis and tumorigenesis and are involved in drug and radiation resistance, metastasis, tumor relapse and initiation. Remarkably, they have other abilities such as inheritance of self-renewal and de-differentiation. Hence, targeting CSCs is considered a potential anti-cancer therapeutic strategy. Recent advances in the identification of biomarkers to recognize CSCs and the development of new techniques to evaluate tumorigenic and carcinogenic roles of CSCs are instrumental to this approach. Elucidation of signaling pathways that regulate CSCs colony progression and drug resistance are critical in establishing effective targeted therapies. CSCs play a central key role in immunomodulation, immune evasion and effector immunity, which alters immune system balancing. These include mTOR, SHH, NOTCH and Wnt/β-catering in cancer progression. In this review article, we discuss the importance of these CSCs pathways in cancer therapy.

Methylglyoxal at metronomic doses sensitizes breast cancer cells to doxorubicin and cisplatin causing synergistic induction of programmed cell death and inhibition of stemness

Potent anticancer activity coupled with absence of toxicity at therapeutic dose established the glycolytic metabolite, methylglyoxal, as a promising candidate against malignant neoplasia. In this preclinical study we illustrate the applicability of methylglyoxal in formulating an optimally designed combination regimen with chemotherapeutic drugs against breast cancer. Results demonstrated a synergistic augmentation in doxorubicin and cisplatin mediated cytotoxicity in human breast cancer cell lines MDA MB 231 & MCF 7 with methylglyoxal co-treatment at metronomic concentrations. The cell death due to combination treatment was significantly prevented by N-Acetylcysteine and the synergistic effects were attenuated in presence of inhibitors for apoptosis and necroptosis, in MDA MB 231 and MCF 7 cells, respectively. Additionally, acridine orange staining and immunoblotting with LC3B antibody indicated the suppression of doxorubicin induced autophagy flux with methylglyoxal co-treatment. This report documents for the first time the preferential targeting of breast cancer stem cells by methylglyoxal. Combination treatment with doxorubicin or cisplatin hindered mammosphere forming efficiency and inclusively eliminated both cancer stem as well as non-stem cancer cells. The synergistic effect was validated in Ehrlich mammary carcinoma cell induced murine ascites model and the combination advantage in vivo was achieved without any additional deleterious effect to liver and kidney. Our present study evidences the implications of methylglyoxal inclusion in adjuvant multimodal chemotherapeutics against breast cancer and offers noteworthy insights into the possible outcome.

SOX8 regulates cancer stem-like properties and cisplatin-induced EMT in tongue squamous cell carcinoma by acting on the Wnt/β-catenin pathway

A sub-population of chemoresistant cells exhibits biological properties similar to cancer stem cells (CSCs), and these cells are believed to be a main cause for tumor relapse and metastasis. In our study, we explored the role of SOX8 and its molecular mechanism in the regulation of the stemness properties and the epithelial mesenchymal transition (EMT) of cisplatin-resistant tongue squamous cell carcinoma (TSCC) cells. We found that SOX8 was upregulated in cisplatin-resistant TSCC cells, which displayed CSC-like properties and exhibited EMT. SOX8 was also overexpressed in chemoresistant patients with TSCC and was associated with higher lymph node metastasis, advanced tumor stage and shorter overall survival. Stable knockdown of SOX8 in cisplatin-resistant TSCC cells inhibited chemoresistance, tumorsphere formation, and EMT. The Wnt/β-catenin pathway mediated the cancer stem-like properties in cisplatin-resistant TSCC cells. Further studies showed that the transfection of active β-catenin in SOX8 stable-knockdown cells partly rescued the SOX8 silencing-induced repression of stem-like features and chemoresistance. Through chromatin immunoprecipitation and luciferase assays, we observed that SOX8 bound to the promoter region of Frizzled-7 (FZD7) and induced the FZD7-mediated activation of the Wnt/β-catenin pathway. In summary, SOX8 confers chemoresistance and stemness properties and mediates EMT processes in chemoresistant TSCC via the FZD7-mediated Wnt/β-catenin pathway.

Targeting Strategies for Renal Cell Carcinoma: From Renal Cancer Cells to Renal Cancer Stem Cells

Renal cell carcinoma (RCC) is a common form of urologic tumor that originates from the highly heterogeneous epithelium of renal tubules. Over the last decade, targeting therapies to renal cancer cells have transformed clinical care for RCC. Recently, it was proposed that renal cancer stem cells (CSCs) isolated from renal carcinomas were responsible for driving tumor growth and resistance to conventional chemotherapy and radiotherapy, according to the theory of CSCs; this has provided the rationale for therapies targeting this aggressive cell population. Precise identification of renal CSC populations and the complete cell hierarchy will accurately inform characterization of disease subtypes. This will ultimately contribute to more personalized and targeted therapies. Here, we summarize potential targeting strategies for renal cancer cells and renal CSCs, including tyrosine kinase inhibitors, mammalian target of rapamycin inhibitors (mTOR), interleukins, CSC marker inhibitors, bone morphogenetic protein-2, antibody drug conjugates, and nanomedicine. In conclusion, targeting therapies for RCC represent new directions for exploration and clinical investigation and they plant a seed of hope for advanced clinical care.

The Role of Hypoxia and Cancer Stem Cells in Renal Cell Carcinoma Pathogenesis

The cancer stem cell (CSC) model has recently been approached also in renal cell carcinoma (RCC). A few populations of putative renal tumor-initiating cells (TICs) were identified, but they are indifferently understood; however, the first and most thoroughly investigated are CD105-positive CSCs. The article presents a detailed comparison of all renal CSC-like populations identified by now as well as their presumable origin. Hypoxic activation of hypoxia-inducible factors (HIFs) contributes to tumor aggressiveness by multiple molecular pathways, including the governance of immature stem cell-like phenotype and related epithelial-to-mesenchymal transition (EMT)/de-differentiation, and, as a result, poor prognosis. Due to intrinsic von Hippel-Lindau protein (pVHL) loss of function, clear-cell RCC (ccRCC) develops unique pathological intra-cellular pseudo-hypoxic phenotype with a constant HIF activation, regardless of oxygen level. Despite satisfactory evidence concerning pseudo-hypoxia importance in RCC biology, its influence on putative renal CSC-like largely remains unknown. Thus, the article discusses a current knowledge of HIF-1α/2α signaling pathways in the promotion of undifferentiated tumor phenotype in general, including some experimental findings specific for pseudo-hypoxic ccRCC, mostly dependent from HIF-2α oncogenic functions. Existing gaps in understanding both putative renal CSCs and their potential connection with hypoxia need to be filled in order to propose breakthrough strategies for RCC treatment.

Common stemness regulators of embryonic and cancer stem cells

Pluripotency of embryonic stem cells (ESCs) and induced pluripotent stem cells is regulated by a well characterized gene transcription circuitry. The circuitry is assembled by ESC specific transcription factors, signal transducing molecules and epigenetic regulators. Growing understanding of stem-like cells, albeit of more complex phenotypes, present in tumors (cancer stem cells), provides a common conceptual and research framework for basic and applied stem cell biology. In this review, we highlight current results on biomarkers, gene signatures, signaling pathways and epigenetic regulators that are common in embryonic and cancer stem cells. We discuss their role in determining the cell phenotype and finally, their potential use to design next generation biological and pharmaceutical approaches for regenerative medicine and cancer therapies.

The epigenetic/noncoding origin of tumor dormancy

Cancer stem cells (CSCs) have been implicated as the seeds of treatment resistance and metastasis, which are the most deadly features of a neoplasm. However, an unequivocal definition of the CSC phenotype is still missing. A common feature of normal and aberrant stem cells is their ability to enter a prolonged dormant state. Cancer dormancy is a key mechanism for treatment resistance and metastasis. Here we propose a unified definition of dormancy-competent CSCs (DCCs) as the neoplastic subpopulation that can plastically alternate periods of dormancy and rapid growth. Irreversible DNA mutations can hardly account for this versatile behavior, and based on emerging evidence we propose that cancer dormancy is a nongenetic disease driven by the flexible nature of the epigenetic/noncoding interactome.

A knockdown of Maml1 that results in melanoma cell senescence promotes an innate and adaptive immune response

Maml1 is emerging as a coactivator of many signaling pathways, including the Notch and Wnt pathways. Targeting Maml1 in melanoma cells efficiently knocks down the downstream transcriptional repressors Hey1 and Hes1, resulting in melanoma cell senescence, cellular differentiation, and increased melanin production. Significantly, higher IFNβ and chemokine gene transcripts have been observed, together with increased STAT1 and decreased STAT3 and NF-κB signaling activities. Although decreased cell proliferation contributes to slower tumor growth in vivo, the depletion of NK and CD8(+) T cells in an shMaml1-B16 tumor carrier mouse leads to more rapid tumor growth than that observed in control shC002-B16 tumors. This result demonstrates that the knockdown of Maml1 transcription and function contributes to increased immune surveillance. The knockdown of Maml1 transcription in the human melanoma cell line M537 also results in senescence, IFNβ upregulation, increased chemokine gene expression, and greater NK and CD8(+) T cell migration in a transwell system. This study demonstrated that targeting Maml1-induced tumor cell senescence and differentiation may alter the tumor microenvironment and cytokine and chemokine profiles and may also promote innate and adaptive immune cell infiltration and function.

Pharmacogenetics and pharmacogenomics: role of mutational analysis in anti-cancer targeted therapy

The goal of cancer pharmacogenomics is to obtain benefit from personalized approaches of cancer treatment and prevention. Recent advances in genomic research have shed light on the crucial role of genetic variants, mainly involving genes encoding drug-metabolizing enzymes, drug transporters and targets, in driving different treatment responses among individuals, in terms of therapeutic efficacy and safety. Although a considerable amount of new targeted agents have been designed based on a finely understanding of molecular alterations in cancer, a wide gap between pharmacogenomic knowledge and clinical application still persists. This review focuses on the relevance of mutational analyses in predicting individual response to antitumor therapy, in order to improve the translational impact of genetic information on clinical practice.

An EZH2 polymorphism is associated with clinical outcome in metastatic colorectal cancer patients

BACKGROUND

Despite therapeutic innovations, metastatic colorectal cancer (mCRC) is still characterized by poor prognosis and few molecular markers predict the risk of progression. Polycomb group genes (PcGs) are epigenetic modifiers involved in tumor suppressor gene silencing. PcG member EZH2 mediates gene silencing through histone-H3 lysine-27 methylation. In colorectal cancer (CRC), EZH2 overexpression predicts shorter survival. Recently, four EZH2 single-nucleotide polymorphisms (SNPs) have been described. The present study was aimed at evaluating the correlation between EZH2 SNPs and outcome parameters in mCRC patients.

PATIENTS AND METHODS

DNA was extracted from blood samples of 110 mCRC patients treated with first-line 5-fluorouracil, folinic acid, irinotecan (FOLFIRI) and bevacizumab. Genotyping was carried out by real-time PCR. Genotype was used to predict objective response, progression-free survival (PFS) and overall survival (OS). EZH2 messenger RNA levels were evaluated on lymphocytes of a parallel cohort of 50 CRC patients.

RESULTS

One allelic variant (rs3757441 C/C versus C/T or T/T) was significantly associated with shorter PFS and OS (P < 0.01 and P < 0.05, respectively). At multivariate analysis, the same variant resulted an independent predictor of PFS and OS (P < 0.05). The C/C variant was associated with significantly higher EZH2 expression (P < 0.05).

CONCLUSION

An EZH2 SNP may be useful to predict clinical outcome in mCRC patients.

Polycomb genes and cancer: time for clinical application?

Polycomb group genes (PcGs) are epigenetic effectors, essential for stem cell self-renewal and pluripotency. Two main Polycomb repressive complexes (PRC1, PRC2) mediate gene silencing through histone post-translational modifications. PcGs have been the focus of investigation in cancer research. Many cancer types show an over-expression of PcGs, predicting poor prognosis, metastasis and chemoresistance. Genetic polymorphisms of EZH2 (a PRC2 component) are significantly associated to lung cancer risk. Recently, 3-Deazaneplanocin A (DZNeP) was identified as an efficient inhibitor of PRC2 activity. DZNeP impairs cancer stem cell self-renewal and tumorigenicity. Despite the well-established role of PcGs in cancer stem cell biology, few studies dissected the clinical significance of these genes. In this paper, we explore PcGs as predictive and prognostic factors in oncology, with particular emphasis on what they can add to current biomarkers. We also propose a model for the rational development of DZNeP-based anticancer regimens and suggest the therapeutic applications of this drug.