Downregulated expression of RACK1 results in pancreatic cancer growth and metastasis

The expression and function of the Receptor for Activated C Kinase 1 (RACK1) in cancer growth and metastasis are confused in different cancers, especially in pancreatic ductal adenocarcinoma (PDAC).

One-hundred and eighty-two PDAC tissue specimens (95 males and 87 females) including pancreatic cancer tissue and para-carcinoma tissue were collected for analysis between 2005 to 2012. Blood phenotypic parameters using cell count and capillary electrophoresis were investigated. HE staining, real time PCR, Western blot analysis, and soft agar assays were performed to determine the role of RACK1.

In this study, we aim to determine the specific role of RACK1 in the untility of PDAC.

We found that RACK1 expression was significantly lower in pancreatic cancer tissue than in para-carcinoma normal pancreatic tissue both in clinic and mice with pancreatic cancer at the early stage. Our results suggested that RACK1 silence could significantly promote cell growth and metastasis of pancreatic cancer cells. But we found that the overexpression of RACK1 has the opposite effect in vitro. In vivo MIAPaca-2 cells overexpressing RACK1, the results demonstrated lower metastatic ability than MIAPaca-2 cells. RACK1 overexpression could decrease the NF-κB transactivation activity of MIAPaca-2 cells, which was consistent with the inhibitory effect of RACK1 overexpression on the pro-migration and pro-invasive target gene of NF-κB, while which could be increased by RACK1 silence. RACK1 silence also enhanced protein expression of pro-migration and pro-invasive NF-κB target genes, which on the contrary, could be reversed by IκBα. Besides, RACK1 expression was significantly associated with lymph node metastasis, vessels metastasis, invasion of nerves as well as TNM staging. The 3-year survival rate of patients with high RACK1 expression was significantly higher than those patients with low RACK1 expression. However, RACK1 expression was not an independent risk factor for of the long-term postoperative survival of patients with pancreatic cancer.

The obtained results in our study suggested that the low expression of RACK1 was associated with cancer cell growth and metastasis in pancreatic cancer through the activation of the NF-κB pathway. RACK1 could be a potential therapeutic drug target to pancreatic cancer and metastasis.