CDK5RAP3

Abstract: We used oligonucleotide microarrays with probe sets to 22,283 genes to analyze the gene expression profile of lung adenocarcinoma. Cancerous and noncancerous tissue samples were obtained from 23 patients with stage I or II lung cancer; 18 tissue pairs and 5 cancerous tissues. A list of 2065 genes that differentiate between cancerous and noncancerous tissues was generated using Winsorized paired t-tests. We analyzed CDK5RAP3 and CCNB2, which are involved in cell cycle progression, and RAGE. The first 2 of these 3 genes proved to be overexpressed in tumor tissue, whereas the RAGE gene was suppressed in tumor tissue. When CDK5RAP3 and CCNB2 were examined in individual patients we found that in cases where one of these genes was only slightly overexpressed the other was highly overexpressed. The combined expression of the 2 cell cycle genes was found to be statistically significant for differentiating between cancerous and noncancerous tissues. Inclusion of the data for the RAGE gene made the differentiation more powerful. The gene expression ratio gave a clear result: when CDK5RAP3 was expressed more than RAGE, the tissue was carcinomatous, and vice versa. We therefore conclude that these 3 genes may be used as a very reliable biomarker of lung adenocarcinoma.

Abstract: CDK5RAP3 was initially isolated as a binding protein of the CDK5 activator p35. Although CDK5RAP3 has been shown to negatively regulate the Wnt/β-catenin signaling pathway in gastric cancer by repressing GSK-3β phosphorylation, its in-depth mechanism has not been determined. Following CDK5RAP3 overexpression or knock down, CDK5RAP3 signaling pathways were investigated in gastric cancer cells by Western Blotting. Cell growth, invasion and migration were also evaluated in gastric cancer cell lines. We analyzed CDK5RAP3, AKT, p-AKT (Ser473), GSK-3β and p-GSK-3β (Ser9) expression in gastric tumor samples and adjacent non-tumor tissues from 295 patients using immunohistochemistry and Western Blotting. The prognostic significance of CDK5RAP3 and p-AKT (Ser473) was confirmed by a Log-rank test. Our study demonstrated that the expression of p-AKT (Ser473) and p-GSK-3β (Ser9) was negatively correlated with CDK5RAP3 in stable gastric cancer cell lines. CDK5RAP3 repressed AKT phosphorylation, which promoted GSK-3β phosphorylation, thereby suppressing β-catenin protein expression and, consequently, gastric cancer. The protein level of CDK5RAP3 was markedly decreased in most gastric tumor tissues compared with adjacent non-tumor tissues, and the levels of p-AKT (Ser473) and p-GSK-3β (Ser9) were also negatively correlated with those of CDK5RAP3. The prognostic value of CDK5RAP3 for overall survival was found to be dependent on AKT phosphorylation. Our results demonstrated that CDK5RAP3 negatively regulates the Wnt/β-catenin signaling pathway by repressing AKT phosphorylation, which leads to better survival of patients with gastric cancer.

Abstract: CDK5 regulatory subunit associated protein 3 (CDK5RAP3) is a novel activator of PAK4 and processes important pro-metastatic function in hepatocarcinogenesis. However, it remains unclear if there are other mechanisms by which CDK5RAP3 promotes HCC metastasis. Here, we showed that in CDK5RAP3 stable knockdown SMMC-7721 HCC cells, p14ARF tumor suppressor was upregulated at protein and mRNA levels, and ectopic expression of CDK5RAP3 was found to repress the transcription of p14ARF. Using chromatin immunoprecipitation assay, we demonstrated that CDK5RAP3 bound to p14ARF promoter in vivo. Furthermore, knockdown of p14ARF in CDK5RAP3 stable knockdown HCC cells reversed the suppression of HCC cell invasiveness mediated by knockdown of CDK5RAP3. Taken together, our findings provide the new evidence that overexpression of CDK5RAP3 promotes HCC metastasis via downregulation of p14ARF.