Current Cancer Drug Targets - Volume 21, Issue 3, 2021

Acid ceramidase (AC), the key enzyme of the ceramide metabolic pathway, hydrolyzes pro-apoptotic ceramide to sphingosine, which is metabolized to mitogenic sphingosine-1-phosphate by the action of sphingosine-1-kinase. The intracellular level of AC determines ceramide/ sphingosine-1-phosphate rheostat, which in turn decides the cell fate. The upregulated AC expression during cancerous condition acts as a “double-edged sword” by converting pro-apoptotic ceramide to anti-apoptotic sphingosine-1-phosphate, wherein on one end, the level of ceramide is decreased, and on the other end, the level of sphingosine-1-phosphate is increased, thus altogether aggravating the cancer progression. In addition, cancer cells with upregulated AC expression exhibited increased cell proliferation, metastasis, chemoresistance, radioresistance and numerous strategies were developed in the past to effectively target the enzyme. Gene silencing and pharmacological inhibition of AC sensitized the resistant cells to chemo/radiotherapy, thereby promoting cell death. The core objective of this review is to explore AC mediated tumour progression and the potential role of AC inhibitors in various cancer cell lines/models.

The central dogma of molecular biology, has remained a cornerstone of classical molecular biology. However, serendipitously discovered microRNAs (miRNAs) in nematodes paradigmatically shifted our current knowledge of the intricate mechanisms during transitions from transcription to translation. Thediscovery of miRNA captured considerable attention and appreciation, and we had witnessed an explosion in the field of non-coding RNAs. Ground-breaking discoveries in the field of non-coding RNAs have helped in better characterization of microRNAs and long noncoding RNAs (LncRNAs). There is an ever-increasing list of miRNA targets that are regulated by MALAT1 to stimulate or repress the expression of target genes. However, in this review, our main focus is to summarize mechanistic insights on MALAT1-mediated regulation of oncogenic signaling pathways. We have discussed how MALAT1 modulated TGF/SMAD and Hippo pathways in various cancers. We have also comprehensively summarized how JAK/STAT and Wnt/β-catenin pathways stimulated MALAT1 expression and consequentially how MALAT1 potentiated these signaling cascades to promote cancer. MALAT1 research has undergone substantial broadening. However, there is still a need to identify additional mechanisms. MALAT1 is involved in the multi- -layered regulation of multiple transduction cascades, and detailed analysis of different pathways will be advantageous in getting a step closer to individualized medicine.

Background: Renal cell carcinoma represents 3% of all adult malignancies. MicroRNAs exhibit specific functions in various biological processes through their interaction with cellular mRNA involved in apoptosis and cell cycle control. Recent studies have reported the potential association of single-nucleotide polymorphisms (SNPs) in miRNA-binding sites of VHL-HIF1α pathway genes with renal cancer development and progression. Objective: The objective of this study is to investigate the SNPs invoking an alteration in the nature of interaction with miRNA binding sites of VHL-HIF1α pathway genes. Methods: Total 450 cases of histologically and clinically verified ccRCC and 490 controls were included in our study. Genotyping was performed using a TaqMan PCR allelic discrimination method. Kaplan-Meier method of statistical analysis was implemented to analyze the overall patient survival rate. Results: Polymorphism rs10491534 in TSC1 gene was significantly associated with the risk of developing advanced ccRCC. Allele G of rs1642742 in VHL gene was significantly prevalent in ccRCC compared with the control group aged 55 and older (OR = 1.5566; CI [1.1532-2.1019]). Results from the dominant model combining individuals with AG or AA genotype showed that the A allele bearers of CDCP1 rs6773576 exhibited a higher risk of death compared to GG carriers (HR 3.93, 95% CI 1.76-17.21, log-rank P = 0.0033). Conclusion: The present study delineated the association of miRNA binding site variants in VHL- HIF1α pathway genes with the ccRCC risk, which may affect the clinical outcomes.

Background: Adipose tissue-derived MSCs engineered with the tumor necrosis factor- related apoptosis-inducing ligand protein (MSCs-TRAIL) have significant anticancer activity. MSCs, without any genetic modifications, exposed to high doses of chemotherapeutic agents are able to uptake the drug and release it in an amount affecting tumor proliferation. The purpose of this study was to verify the ability of MSCs-TRAIL to uptake and release paclitaxel (PTX) by providing an increased antitumor efficacy. Methods: MSCs and MSCs-TRAIL were tested for their sensitivity to Paclitaxel (PTX) by MTT assay, and the cells were loaded with PTX according to a standardized procedure. The secretome was analysed by HPLC for the presence of PTX, microarray assay for soluble TRAIL (s-TRAIL) and tested for in vitro anticancer activity. Results: MSCs-TRAIL were resistant to PTX and able to incorporate and then release the drug. The secretion of s-TRAIL by PTX loaded MSCs-TRAIL was not inhibited, and the PTX delivery together with s-TRAIL secretion resulted in increased antitumor efficacy of cell secretome as tested in vitro on human pancreatic carcinoma (CFPAC-1) and glioblastoma (U87-MG). Conclusion: Our result is the first demonstration of the possible merging of two new MSCs therapy approaches based on genetic manipulation and drug delivery. If confirmed in vivo, this could potentiate the efficacy of MSCs-TRAIL and strongly contribute to reducing the toxicity due to the systemic treatment of PTX.

Background: CYP1B1 is considered as a valuable target for chemotherapy. It catalyzes the bioactivation of naphthoquinone oximes within certain cancer cell lines. However, the expression level of CYP1B1 in melanoma and the functional role regulating the activity of DMAKO-20 as a representative naphthoquinone oxime against skin carcinoma are still unknown. Objective: We sought to examine the expression level of CYP1B1 in melanoma and explore the molecular mechanism behind the anticancer effects of DMAKO-20 in melanoma. Methods: CYP1B1 expression levels in paraffin specimens taken from melanoma patients, and its expression levels in B16/F10 cancer cells were investigated using immunohistochemical staining. The molecular mechanisms behind DMAKO-20 activity against melanoma were investigated by using cytotoxicity, cell scratching, apoptotic, and immunoblotting assays. Results: CYP1B1, the P450 isoform, was expressed at high levels in melanoma tissues and cultured B16/F10 cells but was undetectable in normal tissues or fibroblasts. In cell proliferation assays, the shikonin oxime DMAKO-20 exhibited potent and selective antiproliferative effects against B16/F10 melanoma cells and inhibited migration. Several mechanisms for the anticancer effects of DMAKO-20 have been identified in B16/F10 melanoma cells, including apoptosis, upregulation of mitochondrial apoptotic Bax proteins, and downregulation of anti-apoptotic Bcl-2. The results from these mechanistic investigations indicated that DMAKO-20 underwent CYP1B1-mediated metabolic activation to activate anticancer metabolites within melanoma cells. Conclusion: DMAKO-20 exhibited a selective cytotoxic effect on melanoma cells through CYP1B1-mediated activation. Using DMAKO-20 as a lead compound, further structural optimization may provide new drug entities for the treatments of malignant skin carcinomas.

Background: High risk type 16 of human papillomavirus (HPV16) is associated with 50% of cervical cancer, for which reliable targeted therapies are lacking. HPV early protein 7 (E7) is an oncoprotein responsible for cell malignant transformation. In our previous work, a highly specific affibody targeting HPV16E7 (ZHPV16E7) was developed. Objective: In order to improve the targeted therapeutic effect, the present study prepared an affitoxin consisting of ZHPV16E7 fused with granzyme B (GrB), namely, ZHPV16E7-GrB, and evaluated its targeting action in vitro and in vivo. Methods: The ZHPV16E7-GrB fusion protein was produced in a prokaryotic expression system. The targeted binding properties of the ZHPV16E7-GrB to the HPV16E7 were confirmed by immunofluorescence assay (IFA) in cervical cancer cell lines, by immunohistochemical assay (IHA) in cervical cancer tissue from clinical specimens and by near-infrared imaging in tumour-bearing mice. The anti- tumour effect on both cervical cancer cells in vitro and tumour-bearing mice in vivo were further evaluated. Results: A 34-kDa ZHPV16E7-GrB fusion protein was produced in E. coli and displayed the corresponding immunoreactivity. IFA revealed that ZHPV16E7-GrB bound specifically to HPV16-positive TC-1 and SiHa cells. IHA showed that ZHPV16E7-GrB also bound specifically to HPV16-positive clinical tissue specimens. In addition, the near-infrared imaging results showed that ZHPV16E7-GrB was enriched in tumour tissues. Moreover, both the ZHPV16E7-GrB affitoxin and ZHPV16E7 affibody (without GrB) significantly reduced the proliferation of cervical cancer cells in vitro and tumor-bearing mice in vivo, and the anti-proliferative effect of ZHPV16E7-GrB was higher than that of the ZHPV16E7 affibody. Conclusions: The affitoxin by coupling the affibody with GrB is a promising targeted therapeutic agent with the dual advantages of the targeted affibody and the GrB cytotoxin.

Background: Esophageal squamous cell carcinoma (ESCC) is a major subtype of esophageal cancers. The five-year survival rate of ESCC is low, and molecular targets for ESCC treatment and prognosis assessment are very limited. T cells are critical for the clearance of cancer cells, and blockade of co-inhibitory molecules for T cell activation has emerged as a promising therapy to treat cancer patients. However, in ESCC patients, co-inhibitory molecules regulating T cell activation are poorly documented. Objective: We aim to evaluate how the presence of inhibitory check-point molecules in T cells could impact the survival of patients. Methods: We performed a follow-up study of 161 patients undergoing resection of esophageal carcinoma from February 2014 to December 2015, by immunohistochemical staining of six co-inhibitory molecules for T cell activation, namely PD-1, CTLA-4, TIM-3, LAG-3, BTLA and A2AR. Expression of each of the six co-inhibitory molecules was analyzed for its correlation with patient survival by Kaplan-Meier survival analysis. We also applied Kaplan-Meier analyses to evaluate the concomitant expression of co-inhibitory molecules and their correlation with patient survival. Results: We found that levels of PD-1, TIM-3 and BTLA can be used as independent prognostic factors for the overall survival of patients with ESCC. More importantly, our study found that the co-expression of PD-1 and TIM-3, PD-1 and BTLA, TIM-3 and BTLA significantly reduced the survival of patients with ESCC (P<0.05). Conclusion: Therefore, our results suggest the necessity of evaluating the tumor tissue expression of co-inhibitory molecules and targeting co-expressed molecules in immunotherapies for ESCC patients.

Background: The major challenge to the treatment of advanced colorectal cancer (CRC) is the persistent occurrence of chemoresistance. One of the established etiologies is the existence of cancer stem-like cells (CSCs), due to which, tumors show resistance to external therapeutic challenges. Objective: The forkhead-box A3 (FOXA3) is a potent transcription factor that potentiates the acquisition and maintenance of stemness fate in many physiological systems. However, its effect on cancer stemness, particularly treatment, has not been explored in CRC, forming the basis of the current study. Methods: FOXA3 expression in oxaliplatin-resistant CRC tissues and cells was evaluated using RT-qPCR. Effects of FOXA3 manipulation on sensitivity to oxaliplatin were assessed using WST-1, apoptotic ELISA, colony formation and xenograft model. Effects of FOXA3 alteration on CSCs were determined using tumorsphere assay and CD44 staining. Transcriptional regulation of MACC1 by FOXA3 was studied using ChIP, Co-IP and luciferase reporter assay. Results: FOXA3 expression was significantly reduced in tumor samples from oxaliplatin-non-responsive patients compared with that in tumor samples from oxaliplatin-sensitive patients. This downregulation of FOXA3 expression predicted a poor post-chemotherapy overall- or disease-free survival in our 117-patient cohort. FOXA3 down-regulation significantly enhanced cell survival and stem-like properties, thus rendering the CRC cells unresponsiveness to oxaliplatin-induced cell death. Mechanistically, the anti-neoplastic effect of FOXA3 was mediated mainly through transcriptional repression of metastasis-associated in colon cancer 1 (MACC1) in oxaliplatin-resistant CRC cells. Conclusion: Our findings establish FOXA3 as a potent tumor suppressor in CRC, which may disrupt the maintenance of stemness and modulate sensitivity to oxaliplatin by inhibiting the transcription of MACC1 within CRC cells.