Objective:To investigate the effect of decreasing DKC1 gene expression on radiosensitivity of HeLa cells.Methods:A cell model with low expression of DKC1 gene was established by shRNA technology with lentivirus as vector, and the interference efficiency was verified by RT-PCR and Western blot assay. Cells were divided into two groups of interference (Lv-shDKC1) and its negative control. Telomerase activity was detected by TRAP-ELISA, and telomere length was measured by Real-time PCR. Cell survival was obtained through clone formation assay and fitted by multi-target single-hit model, and radiobiological parameters ( D0, Dq, N, SF2) and radiosensitization ratio (SER) were calculated. Results:After DKC1 interfering, the expression levels of mRNA and protein of DKC1 in HeLa cells were significantly decreased by (71.330±4.112)% ( t=25.53, P<0.05) and (35.520±3.804)% ( t=4.833, P<0.05), respectively. Compared with the blank control group and negative control group, the telomerase activity of Lv-shDKC1 group decreased significantly from 0.900±0.044 and 0.897±0.031 to 0.713±0.021 ( F=31.44, P<0.05), the relative telomere length was significantly decreased from 4.233±0.306 and 4.633±0.379 to 2.667±0.404 ( F=39.15, P<0.05). The telomerase activity and relative telomere length of blank control group and Lv-shDKC1 negative control group had no significant difference( P>0.05). SF2 in the interference group (0.571±0.006) was significantly lower than that of the blank control group (0.861±0.009) and the Lv-shDKC1 negative control group (0.807±0.002) ( F=1812, P<0.05), and the radiosensitization ratio (SER) of shDKC1 interference was 1.508. Conclusions:Downregulation of DKC1 in human cervical cancer HeLa cells enhances the radiosensitivity through inhibiting the activity of telomerase and shortening the length of telomere. DKC1 gene may become a new target of radiosensitization.

Pancreatic cancer is a more aggressive and refractory malignancy. Resistance and toxicity limit drug efficacy. Herein, we report a lower toxic and higher effective miriplatin (MPt)-loaded liposome, LMPt, exhibiting totally different anti-cancer mechanism from previously reported platinum agents. Both in gemcitabine (GEM)-resistant/sensitive (GEM-R/S) pancreatic cancer cells, LMPt exhibits prominent anti-cancer activity, led by faster cellular entry-induced larger accumulation of MPt. The level of caveolin-1 (Cav-1) determines entry rate and switch of entry pathways of LMPt, indicating a novel role of Cav-1 in nanoparticle entry. After endosome-lysosome processing, in unchanged metabolite, MPt is released and targets mitochondria to enhance binding of mitochondria protease LONP1 with POLG and TFAM, to degrade POLG and TFAM. Then, via PINK1-Parkin axis, mitophagy is induced by POLG and TFAM degradation-initiated mitochondrial DNA (mtDNA) replication blocking. Additionally, POLG and TFAM are identified as novel prognostic markers of pancreatic cancer, and mtDNA replication-induced mitophagy blocking mediates their pro-cancer activity. Our findings reveal that the target of this liposomal platinum agent is mitochondria but not DNA (target of most platinum agents), and totally distinct mechanism of MPt and other formulations of MPt. Self-assembly offers LMPt special efficacy and mechanisms. Prominent action and characteristic mechanism make LMPt a promising cancer candidate.

Pancreatic adenocarcinoma (PAAD) is one of the most lethal malignancies. Although gemcitabine (GEM) is a standard treatment for PAAD, resistance limits its application and therapy. Secoemestrin C (Sec C) is a natural compound from the endophytic fungus Emericella, and its anticancer activity has not been investigated since it was isolated. Our research is the first to indicate that Sec C is a broad-spectrum anticancer agent and could exhibit potently similar anticancer activity both in GEM-resistant and GEM-sensitive PAAD cells. Interestingly, Sec C exerted a rapid growth-inhibiting effect (80% death at 6 h), which might be beneficial for patients who need rapid tumor shrinkage before surgery. Liquid chromatography/mass spectrometry and N-acetyl-l-cysteine (NAC) reverse assays show that Sec C sulfates cysteines to disrupt disulfide-bonds formation in endoplasmic reticulum (ER) proteins to cause protein misfolding, leading to ER stress and disorder of lipid biosynthesis. Microarray data and subsequent assays show that ER stress-mediated ER-associated degradation (ERAD) ubiquitinates and downregulates YAP to enhance ER stress via destruction complex (YAP-Axin-GSK-βTrCP), which also elucidates a unique degrading style for YAP. Potent anticancer activity in GEM-resistant cells and low toxicity make Sec C a promising anti-PAAD candidate.