BRCA1 epigenetic inactivation predicts sensitivity to platinum-based chemotherapy in breast and ovarian cancer

Germline mutations in the BRCA1 or BRCA2 genes are associated with an increased risk of breast and ovarian cancer development. Both genes are involved in DNA repair, and tumors harboring genetic defects in them are thought to be more sensitive to DNA-damaging agents used in chemotherapy. However, as only a minority of breast and ovarian cancer patients carry BRCA1 or BRCA2 mutations, few patients are likely to benefit from these pharmacogenetic biomarkers. Herein, we show that, in cancer cell lines and xenografted tumors, BRCA1 CpG island promoter hypermethylation-associated silencing also predicts enhanced sensitivity to platinum-derived drugs to the same extent as BRCA1 mutations. Most importantly, BRCA1 hypermethylation proves to be a predictor of longer time to relapse and improved overall survival in ovarian cancer patients undergoing chemotherapy with cisplatin.     

Cytoplasmic APE1 promotes resistance response in osteosarcoma patients with cisplatin treatment

Chemotherapy resistance has become a hold back and major clinical challenge in osteosarcoma cancer. The alteration and subcellular distribution of apurinic/apyrimidinic endonuclease 1 (APE1) has been reported to be involved in chemotherapy resistance in many cancers. Here, we report that the cytoplasmic distribution of APE1 plays a key role in the sensitivity of combination platinum chemotherapy in osteosarcoma. Interestingly, the prevalence of cisplatin-induced DNA damage and apoptosis in low cytoplasmic APE1 osteosarcoma cell lines was higher than in high expression of cytoplasmic APE1 cell lines. Overexpression of cytoplasmic APE1 protected the osteosarcoma cells from CDDP-induced apoptosis. In addition, clinical data also show that the level of cytoplasmic APE1 was negatively associated with sensitivity to combination chemotherapy of cisplatin in osteosarcoma patients. Our findings suggest that cytoplasmic APE1 plays a significant role in chemotherapy resistance. This role is a supplement to the extranuclear function of APE1, and cytoplasmic APE1 expression level could be a promising predictor of platinum treatment prognosis for osteosarcoma patients.     

Anticancer Metal Complexes: Synthesis and Cytotoxicity Evaluation by the MTT Assay

Titanium (IV) and vanadium (V) complexes are highly potent anticancer agents. A challenge in their synthesis refers to their hydrolytic instability; therefore their preparation should be conducted under an inert atmosphere. Evaluation of the anticancer activity of these complexes can be achieved by the MTT assay.The MTT assay is a colorimetric viability assay based on enzymatic reduction of the MTT molecule to formazan when it is exposed to viable cells. The outcome of the reduction is a color change of the MTT molecule. Absorbance measurements relative to a control determine the percentage of remaining viable cancer cells following their treatment with varying concentrations of a tested compound, which is translated to the compound anticancer activity and its IC₅₀ values. The MTT assay is widely common in cytotoxicity studies due to its accuracy, rapidity, and relative simplicity.Herein we present a detailed protocol for the synthesis of air sensitive metal based drugs and cell viability measurements, including preparation of the cell plates, incubation of the compounds with the cells, viability measurements using the MTT assay, and determination of IC₅₀ values.     

Exosomal transfer of miR-106a-5p contributes to cisplatin resistance and tumorigenesis in nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC), a subclass of cancers of the neck and head, is a predominant cause of cancer-associated death worldwide. Hence, there is a critical need for research into NPC-related treatment strategies. Cisplatin is a promising therapy option for NPCs and other cancers that is frequently utilized. Some patients acquire resistance to cisplatin therapy, which complicates the successful use of cisplatin treatment in NPCs. Although exosomal transfer of oncogenic miRNAs has been shown to improve recipient cell proliferation, metastasis and chemoresistance, the molecular mechanism behind this effect on NPC has yet to be fully understood. Exosomal microRNAs (miRNAs) from cisplatin-resistant cells were identified as significant mediators of chemoresistance in NPC cells in this investigation. Initially, we found that exosomal miR-106a-5p levels in the serum of chemoresistant and last-cycle patients were greater than in that of non-resistant and first-cycle patients. Also, exosomal miR-106a-5p enhanced the proliferative ability of NPC cells. Mechanistically, exosomal miR-106a-5p targets ARNT2, which further activates AKT phosphorylation, and thus promotes NPC cell proliferation, decreases apoptosis and in turn regulates tumorigenesis. We found similar results using in vivo NPC models, where exosomal miR-106a-5p through regulation of ARNT2 (aryl hydrocarbon receptor nuclear translocator 2) promoted tumorigenesis. Taken together, these findings indicate that exosomal miR-106a-5p could be a promising diagnostic biomarker and drug target for patients with NPC.     

Protection by ebselen against cisplatin-induced nephrotoxicity: Antioxidant system

This study was designed to investigate the cisplatin-induced alteration in renal antioxidant system and the nephroprotection with ebselen. Male Wistar rats were injected with (1) vehicle control; (2) cisplatin; (3) ebselen; and (4) cisplatin plus ebselen. Rats were sacrificed three days post-treatment and plasma as well as kidney were isolated and analyzed. Plasma creatinine increased 598% following cisplatin administration alone which decreased by 158% with ebselen pretreatment. Cisplatin-treated rats showed a depletion of renal glutathione (GSH) levels (52% of control), while cisplatin plus ebselen injected rats had GSH values close to the controls. Antioxidant enzymes superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-Px) activities decreased 38, 75 and 62% of control, respectively, and malondialdehyde (MDA) levels increased 174% of control following cisplatin administration, which were restored to control levels after ebselen treatment. The renal platinum level did not significantly change with ebselen pretreatment. This study suggests that the protection offered by ebselen against cisplatin-induced nephrotoxicity is partly related to the sparing of antioxidant system.     

LncRNA SNHG6 knockdown inhibits cisplatin resistance and progression of gastric cancer through miR-1297/BCL-2 axis

Cisplatin (DDP) resistance is a huge obstacle to gastric cancer (GC) treatment. Long non-coding RNAs (lncRNAs) have been manifested to exert pivotal functions in GC development. Herein, we aimed to explore the functional impact of lncRNA small nucleolar RNA host gene 6 (SNHG6) on DDP resistance and progression of GC. Quantitative real-time PCR (qRT-PCR) assay or Western blotting was performed to detect the expression of SNHG6, microRNA(miR)-1297, and epithelial–mesenchymal transition (EMT)-related factors and B-Cell Lymphoma 2 (Bcl-2) in DDP-resistant GC cells. Half inhibition concentration (IC50) to DDP, clonogenicity, apoptosis and invasion were examined via CCK-8 assay, colony formation assay, flow cytometry and Transwell assay, respectively. Target association between miR-1297 and SNHG6 or BCL-2 was demonstrated via dual-luciferase reporter assay or RIP assay. Xenograft models in nude mice were formed to investigate role of SNHG6 in vivo. We found that SNHG6 and BCL-2 were up-regulated, while miR-1297 expression was declined in GC tissues and DDP-resistant cells. Moreover, depletion of SNHG6 or gain of miR-1297 could repress DDP resistance, proliferation and metastasis of DDP-resistant cells, which was weakened by miR-1297 inhibition or BCL-2 overexpression. Besides, SNHG6 positively regulated BCL-2 expression by sponging miR-1297. Furthermore, SNHG6 knockdown repressed GC tumor growth in vivo. In a word, lncRNA SNHG6 knockdown had inhibitory effects on DDP resistance and progression of GC by sponging miR-1297, highlighting its potential in GC treatment.     

The bromodomain inhibitor JQ1 triggers growth arrest and apoptosis in testicular germ cell tumours in vitro and in vivo

Type II testicular germ cell cancers (TGCT) are the most frequently diagnosed tumours in young men (20–40 years) and are classified as seminoma or non‐seminoma. TGCTs are commonly treated by orchiectomy and chemo‐ or radiotherapy. However, a subset of metastatic non‐seminomas (embryonal carcinomas) displays only incomplete remission or relapse and requires novel treatment options. Recent studies have shown effective application of the small‐molecule inhibitor JQ1 in tumour therapy, which interferes with the function of ‘bromodomain and extraterminal (BET)’ proteins. JQ1‐treated TGCT cell lines display up‐regulation of genes indicative for DNA damage and cellular stress response and induce cell cycle arrest. Embryonal carcinoma (EC) cell lines, which presented as JQ1 sensitive, display down‐regulation of pluripotency factors and induction of mesodermal differentiation. In contrast, seminoma‐like TCam‐2 cells tolerated higher JQ1 concentrations and were resistant to differentiation. ECs xenografted in vivo showed a reduction in tumour size, proliferation rate and angiogenesis in response to JQ1. Finally, the combination of JQ1 and the histone deacetylase inhibitor romidepsin allowed for lower doses and less frequent application, compared with monotherapy. Thus, we propose that JQ1 in combination with romidepsin may serve as a novel therapeutic option for (mixed) TGCTs.