Loss of KAP3 decreases intercellular adhesion and impairs intracellular transport of laminin in signet ring cell carcinoma of the stomach.

Signet-ring cell carcinoma (SRCC) is a unique subtype of gastric cancer that is impaired for cell-cell adhesion. The pathogenesis of SRCC remains unclear. Here, we show that expression of kinesin-associated protein 3 (KAP3), a cargo adaptor subunit of the kinesin superfamily protein 3 (KIF3), a motor protein, is specifically decreased in SRCC of the stomach. CRISPR/Cas9-mediated gene knockout experiments indicated that loss of KAP3 impairs the formation of circumferential actomyosin cables by inactivating RhoA, leading to the weakening of cell-cell adhesion. Furthermore, in KAP3 knockout cells, post-Golgi transport of laminin, a key component of the basement membrane, was inhibited, resulting in impaired basement membrane formation. Together, these findings uncover a potential role for KAP3 in the pathogenesis of SRCC of the stomach.

SOX2 enhances cell survival and induces resistance to apoptosis under serum starvation conditions through the AKT/GSK-3ß signaling pathway in esophageal squamous cell carcinoma.

The human SOX2 gene was recently identified as a novel major oncogene, recurrently amplified and overexpressed in esophageal squamous cell carcinoma (ESCC). However, the role and molecular mechanism of SOX2 in the carcinogenesis of ESCC remain to be elucidated. The present study investigated the effect of SOX2 on ESCC cell survival and resistance to apoptosis under serum starvation conditions. An adenoviral vector-mediated expression system and RNA interference were used to study the effect of SOX2. The present results revealed that SOX2 promoted ESCC cell survival and enhanced resistance to apoptosis under serum starvation conditions, but not in culture conditions with serum. Mechanistically, SOX2 increased the expression levels of phosphorylated AKT and glycogen synthase kinase-3ß (GSK-3ß), a downstream factor of AKT, under serum starvation conditions, leading to the promotion of ESCC cell survival. Additionally, SOX2 activated AKT through the PTEN/PI3K/phosphoinositide-dependent protein kinase 1 and mammalian target of rapamycin complex 2 signaling pathways. Therefore, SOX2 may facilitate the survival of ESCC cells under poor nutrient conditions by activating the AKT/GSK-3ß signaling pathway.

Oncogenic miR-96-5p inhibits apoptosis by targeting the caspase-9 gene in hepatocellular carcinoma.

The aberrant expression or alteration of microRNAs (miRNAs/miRs) contributes to the development and progression of cancer. In the present study, the functions of miR-96-5p in hepatocellular carcinoma (HCC) were investigated. It was identified that miR-96-5p expression was significantly upregulated in primary HCC tumors compared with their non-tumorous counterparts. A copy number gain was frequently observed at chromosomal region 7q32.2 in which the MIR96 locus is located, suggesting that gene amplification may be one of the mechanisms by which miR-96-5p expression is increased in HCC. Transfection of miR-96-5p mimic into HCC cells decreased the expression of CASP9, which encodes caspase-9, the essential initiator caspase in the mitochondrial apoptotic pathway, at the mRNA and protein levels. A putative binding site for miR-96-5p was identified in the CASP9 3'-untranslated region, and the results of a luciferase assay indicated that CASP9 is a potential direct target of miR-96-5p. The miR-96-5p mimic increased resistance to doxorubicin- and ultraviolet-induced apoptosis through the decrease in caspase-9 expression in HCC cells. Transfection of miR-96-5p inhibitor enhanced the cytotoxic effect of doxorubicin by increasing caspase-9 expression in the HCC cells, suggesting a synergistic effect between the miR-96-5p inhibitor and doxorubicin. In conclusion, the results of the present study suggest that miR-96-5p, which is frequently upregulated in HCC, inhibits apoptosis by targeting CASP9. Therefore, miR-96-5p may be a potential therapeutic target for HCC.