Receptor for activated C kinase 1 (RACK1) promotes the progression of OSCC via the AKT/mTOR pathway

Abstract

Our previous study suggested that receptor for activated C kinase 1 (RACK1) contribute to the progression of oral squamous cell carcinoma (OSCC). The aim of this study is to elucidate the mechanism by which RACK1 regulates cell growth in OSCC using in vitro and in vivo models. The effects of RACK1 knockdown with lentivirus based shRNA in stable cell lines were evaluated by Q-PCR and western blot analysis. RACK1 silencing effects on the cell cycle in OSCC cells were detected by flow cytometry and western blot analysis. The effect of RACK1 silencing on inhibiting the progression of OSCC was illustrated using a xenografted mouse model. RACK1 and relevant signaling pathways were investigated in tissues and cells using immunohistochemistry and/or western blot analysis. Stable silencing of the RACK1 gene resulted in a distinct G1 and G2 phase arrest by downregulating Cyclin B1 and Cyclin D1. Depleted RACK1 led to markedly decreased tumor volume and the expression of Ki67, CD34, and VEGF in vivo. The expression of RACK1 and p-AKT has a parallel pattern in different stages of oral carcinogenesis tissues. In addition, the protein level of RACK1 was positively correlated with p-AKT in OSCC tissue samples and cell lines. We found specific transient knockdown of RACK1 could downregulate the protein levels of p-AKT, p-mTOR, and p-S6 in a dose-dependent manner. This study demonstrates that RACK1-dependent OSCC growth and survival may be related to the increased activation of the AKT/mTOR/S6 pathway.

Overexpression of RACK1 Promotes Metastasis by Enhancing Epithelial-Mesenchymal Transition and Predicts Poor Prognosis in Human Glioma

“…We also firstly discovered that the protein levels of G1/S transition key regulators, Cyclin D1 and CDK6, were remarkably reduced when RACK1 was silenced both in U87 and U251 cells. Concordantly with our results, Li et al reported that RACK1 was highly expressed in pancreatic ductal adenocarcinoma (PDAC) and could induce G1/S cell cycle arrest by decreasing the expression of Cyclin D1 [31], while Zhang et al reported that overexpression of RACK1 contributed to the progression of oral squamous cell carcinoma (OSCC) and stable silencing of RACK1 resulted in a distinct G1 and G2 phase arrest by downregulating Cyclin B1 and Cyclin D1 [33]. …”

RACK1 promotes cancer progression by increasing the M2/M1 macrophage ratio via the NF‐κB pathway in oral squamous cell carcinoma

“…To uncover the biological function of RACK1 during macrophage recruitment in OSCC, both cell migration and invasion assays were performed. First, a stable HSC‐3 cell line with low RACK1 expression (sh‐RACK1) and a stable HSC‐4 cell line with RACK1 overexpression (OE‐RACK1) were generated as previously described (Zhang et al , ). Then, we investigated the migration abilities of macrophages after coculture with conditioned media from OSCC cells with different levels of RACK1 expression.…”

“…THP‐1 monocytes were cultured in RPMI medium supplemented with 10% FBS. The generation of stable HSC‐3 cells with low RACK1 expression (sh‐RACK1) and HSC‐4 cells with RACK1 overexpression (OE‐RACK1) was performed as previously described (Zhang et al , ). All cells were cultured under a humidified atmosphere with 5% CO 2 at 37 °C.…”

“…RACK1 has been confirmed to take part in multiple biological events, including cell migration (Li et al, 2012b), virus infection (Majzoub et al, 2014), neural development (Wehner et al, 2011;Xu et al, 2015), angiogenesis (Berns et al, 2000;Zhou et al, 2014) and cancer metastasis (Li et al, 2012a). In our previous study, we found that RACK1, an organ-specific prognostic predictor in OSCC, could promote the malignant biological behavior of OSCC (Liu et al, 2018b;Zhang et al, 2016). However, the effect of RACK1 on the tumor immunological microenvironment in OSCCs is poorly understood.…”

RACK1 promotes lung cancer cell growth via an MCM7/RACK1/Akt signaling complex

“…Zhang et al . reported that stable RACK1 knockdown downregulated Cyclin B1 and Cyclin D1 and promoted G1 and G2 phase arrest in oral squamous cell carcinoma [47]. Interestingly, RACK1 has the opposite effect in colon cancer cells; RACK1 overexpression delays passage of HT-29 cells through G1 and mitotic checkpoints by suppressing Src-mediated Sam68 phosphorylation and maintaining the active state of CDK1-cyclinB [48, 49].…”