Ubiquitin expression in primary 23132/87 and metastatic MKN45 gastric cancer cell lines and differential response to polyubiquitin UBB and UBC gene silencing.

Gastric cancer is one of the most lethal tumors worldwide; it ranks as the 5th most common malignancy and the 3rd most lethal, with over 1 million new diagnoses and over 780’000 deaths in 2018 alone. The outcome of the disease is greatly influenced by tumor stage at the time of diagnosis; unfortunaterly, most patients are diagnosed only after the tumor has already metastasized, which dramatically reduces their chances of survival. Therefore, additional knowledge regarding gastric cancer is needed to define possible biomarkers and therapeutic targets that may respectively improve early detection protocols and treatment. To this end, we compared the asset and regulation of ubiquitin pools in two gastric cancer cell lines: the primary line 23132/87 and the metastatic MKN45. The two cell lines were analyzed in various aspects, such as the relative ubiquitin content and the expression patterns of the four ubiquitin genes UBC, UBB, UBA52 and RPS27A; the mRNA and protein levels of three transcription factors, HSF1, YY1 and SP1, were also measured in light of their involvement in the regulation of some of the ubiquitin genes. Then we performed a series of siRNA-mediated knockdown experiments targeting the two polyubiquitin genes UBB and UBC to investigate if and how different alterations of the ubiquitin content would affect the two cell lines. To briefly summarize our results, the primary gastric cancer cell line 23132/87 exhibits a higher reliance on its endogenous ubiquitin production for survival than the metastatic line MKN45, identifying UBB and UBC as prosurvival genes in 23132/87 primary cells.