The Role of Cdk5 in Retinoic Acid-Induced Apoptosis of Cervical Cancer Cell Line

Abstract

Cdk5 is a small serine/threonine protein kinase which belongs to Cdk family. Unlike other Cdk members. so far Cdk5 is known to be irrelevant in cell cycle. Cdk5 kinase activity is regulated by binding with its activator, p35. Our previous results indicate that Cdk5 and p35 are involved in drugs-induced apoptosis of prostate cancer cells. Retinoic acid (RA) is one of the vitamin A-related compounds. Because of its potency on biological functions, it has been widely studied in its novel actions including the ability to inhibit cancer cell growth and to induce apoptosis. Here, we report that RA treatment decreased the growth of human cervical cancer cell line, HeLa, and Cdk5 contributed to this effect. The involvement of Cdk5 in RA-reduced cell survival was performed by treatments of Cdk5 inhibitor and siRNA. We further identified that RA-induced growth inhibition was partly correlated to Cdk5 activity-related apoptosis by detecting cell cycle distribution of sub G1 phase and the signals of Annexin V staining. In addition, our results also indicated that Cdk5 activity was involved in RA-induced HeLa apoptosis by detecting cleavages of caspase-3 and its substrate, PARP (poly (ADP-ribose) polymerases). Interestingly, the nuclear localizations of Cdk5 and p35 proteins were increased by RA treatment, which, again, suggests the involvement of Cdk5 and p35 in RA-induced apoptotic effects. In conclusion, we provide evidence to suggest that Cdk5 and p35 might play important roles in RA-induced HeLa apoptosis

All-Trans Retinoic Acid Induces DU145 Cell Cycle Arrest through Cdk5 Activation

“…si cdk5 and nonspecific control siRNAs were purchased from Dharmacon (Lafayette, CO) which are SMARTpool™-containing four SMART-selected siRNA duplexes. The siRNAs were transfected into DU145 cells using Lipofectamine™ 2000 (Invitrogen Co., Carlsbad, CA) with 5 pmol siRNA/10 4 cells one day before treatment with ATRA [5,22]. …”

“…Antibodies used included anti-Cdk5 antibody, (1:1,000, Santa Cruz Biotechnology, Santa Cruz, CA), anti-p27 antibody (1:2,500, BD Biosciences, Franklin Lakes, NJ), anti-actin (1:2,000, MAB1501, Millipore, Billerica, MA), and peroxidase-conjugated anti-mouse or anti-rabbit antibodies (1:10,000, Jackson ImmunoResearch Laboratory, West Grove, PA). ECL detection reagent (Perkin Elmer Co., Boston, MA) was used to detect the immunoreactive proteins [5,22]. …”

“…All-trans-retinoic acid (ATRA) is a vitamin A-related compound that can induce apoptosis in tumor cells from many types of cancer, including prostate cancer [1,2], hematopoietic malignancies [3], neuroblastoma [4], cervical carcinoma [5], head and neck carcinomas [6], non-small cell lung cancers [7], breast cancer [8], bladder cancer [9], and ovarian cancer [10]. Prostate cancer is the most common cancer in the world diagnosed among elderly men [2].…”

“…In addition to the roles of Cdk5-p35 in the nervous system, numerous extra-neuronal functions of Cdk5-p35 have been discovered in recent years [17,18,19]. Our previous study indicated that Cdk5 regulates the growth of thyroid cancer cells [20] and that Cdk5 is also important to the ATRA-affected cell cycle distribution and fate of cancer cells [5,21]. Subsequently, we found that the abnormal activation of Cdk5 triggered by intracellular calcium increase is involved in the apoptosis of prostate cancer cells [22].…”

Cyclin-dependent kinase 5 modulates STAT3 and androgen receptor activation through phosphorylation of Ser727 on STAT3 in prostate cancer cells

“…Recently, p35 was indicated to play important roles in human cancers by regulating Cdk5 activity (15,26,27,36), and p35 overexpression was also reported in metastatic prostate cancers (36). Multiple functions of Cdk5 in addition to those in the central nervous system were recently discovered, such as its roles in cancer biology (6,22,26,27,36). In our previous research, we first identified the kinase activity and apoptotic role of Cdk5 in prostate cancer cells (27).…”