Expression of set is downregulated by rapamycin in human colorectal cancer cells

Abstract

Abstract. The purpose of this study was to determine the mechanism through which rapamycin treatment affects the expression of the set gene in human colorectal adenocarcinoma cells. The effect of rapamycin treatment on set expression was evaluated by assessing the mRNA and protein expression of set in the SW480 and LoVo human colon carcinoma cell lines following treatment with rapamycin by quantitative polymerase chain reaction (qPCR) and western blot analysis, respectively. Our results demonstrated that the mRNA and protein levels of set were significantly decreased subsequent to rapamycin treatment in the two cell lines, indicating that set expression may be downregulated by rapamycin in human colorectal adenocarcinoma cells. Our findings suggested that the mammalian target of rapamycin signaling pathway may play a role in tumorigenesis through the regulation of the set gene. IntroductionColorectal adenocarcinoma is the second leading cause of malignancy-related mortality worldwide (1,2), with a continuously increasing prevalence. Several factors and genes, regulating a number of pathways, are involved in colorectal tumorigenesis. Therefore, it is important to investigate the roles of these factors and genes in colorectal adenocarcinoma to promote early diagnosis, therapeutic development and cancer prevention.A total of 86 differentially expressed sequence tags (dbESTs) from human colorectal adenocarcinoma tissues were previously identified by cDNA subtractive library construction and cDNA microarray analysis (3,4). One of these dbESTs, ES274071 (GenBank accession no. NM003011.3; gene name, set) was selected for further investigation. The set gene is located on human chromosome 9p34 and encodes a 277-amino acid protein with a molecular weight of 39 kDa. The set gene was previously found to be involved in the progression of leukemia and ovarian cancer. In a previous study by our group, quantitative reverse transcription polymerase chain reaction (qRT-PCR) analysis revealed that the mRNA level of set in colorectal cancer tissues was higher compared to that in the adjacent normal colorectal tissues, suggesting the involvement of set in the development of human colorectal adenocarcinoma (5).The PI3K/Akt/mammalian target of rapamycin (mTOR) pathway plays a pivotal role in the development and progression of colorectal cancer by regulating cancer cell proliferation, resistance to apoptosis, angiogenesis and metastasis (6). The mTOR protein is a key kinase downstream of the growth factor receptor PI3K and the Akt signaling pathway, which are both involved in the modulation of cell growth, survival, metabolism and proliferation (7). Significant advancements have been made in elucidating the role of mTOR in cancer development and progression. Activation of the mTOR signaling pathway is often the result of genetic alterations of negative regulators of mTOR, such as phosphatase and tensin homolog (PTEN), tuberous sclerosis complex (TSC) 1 and TSC2 (8). It was demonstrated that the activation of the PI3K̸Akt̸mTOR pathway c...

CENPH Inhibits Rapamycin Sensitivity by Regulating GOLPH3-dependent mTOR Signaling Pathway in Colorectal Cancer

“…It has been well established that mTOR pathway plays an essential role in the development and progression of CRC 30 , 31 . As mTOR inhibitors, temsirolimus and everolimus had been approved by FDA for the treatment of patients with metastatic renal cell carcinoma 32 , 33 .…”

“…As mTOR inhibitors, temsirolimus and everolimus had been approved by FDA for the treatment of patients with metastatic renal cell carcinoma 32 , 33 . Although rapamycin (sirolimus) was usually used as immunosuppressant for organ transplantation 34 , the role of rapamycin in inhibiting the protein kinase activity of mTOR and anitproliferative ability makes it a potential anticancer agent 30 , 31 . Preclinical studies have suggested that the combination of rapamycin with a VEGF antibody or trastuzumab exhibited a synergistic antitumor effect in a pancreatic or breast cancer model, respectively 35 , 36 .…”