Protein kinase C-alpha is expressed and activated during the development of renal cell carcinoma

MZF-1/Elk-1/PKCα is Associated with Poor Prognosis in Patients with Hepatocellular Carcinoma

Background: Protein kinase C alpha (PKCα) is a key signaling molecule in human cancer development. As a therapeutic strategy, targeting PKCα is difficult because the molecule is ubiquitously expressed in non-malignant cells. PKCα is regulated by the cooperative interaction of the transcription factors myeloid zinc finger 1 (MZF-1) and Ets-like protein-1 (Elk-1) in human cancer cells.

Methods: By conducting tissue array analysis, herein, we determined the protein expression of MZF-1/Elk-1/PKCα in various cancers.

Results: The data show that the expression of MZF-1/Elk-1 is correlated with that of PKCα in hepatocellular carcinoma (HCC), but not in bladder and lung cancers. In addition, the PKCα down-regulation by shRNA Elk-1 was only observed in the HCC SK-Hep-1 cells. Blocking the interaction between MZF-1 and Elk-1 through the transfection of their binding domain MZF-1_60-72 decreased PKCα expression. This step ultimately depressed the epithelial-mesenchymal transition potential of the HCC cells.

Conclusion: These findings could be used to develop an alternative therapeutic strategy against patients with the PKCα-derived HCC.

Inhibition of PKCα reduces the ability of migration of kidney cancer cells but has no impact on cell apoptosis

Kidney cancer is among the most important causes of cancer-associated mortality worldwide. The present study aimed to evaluate protein kinase C α (PKCα) expression in kidney cancer tissues and cell lines, and its significance in apoptosis and migration. Expression of PKCα was analyzed using quantitative polymerase chain reaction and western blotting. In addition, the inhibitor of PKCα (calphostin C and GO6976) was used to treat kidney cancer cells. The ACHN cell line was generated with PKCα-small-interfering RNA (siRNA) and a stable expression of PKCα, in order to facilitate the analysis of apoptosis and migration of PKCα during knockdown and inactivation. Flow cytometry was used to determine the rates of apoptosis. Immunohistochemical staining was used to identify the localization of PKCα in renal clear cell carcinoma and normal sections. PKCα expression in normal tissues was found to be greater than in cancerous tissues. Furthermore, apoptosis was not promoted with PKCα inhibitors or PKCα-siRNA treatment, and a decrease of the migration ability was observed following transfection with PKCα-dominant negative. The results indicated that inhibition of PKCα might not contribute to apoptosis progression in kidney carcinoma.

PKCα is involved in the progression of kidney carcinoma through regulating netrin-1/UNC5B signaling pathway

With a special interest towards a better understanding of signal pathways, we attempted to discover a safer and more effective therapeutic strategy for kidney carcinoma. Recent studies had suggested a role mediated by PKCα for netrin-1 and its receptors in the initiation and progression of tumors. Real-time PCR and western blotting were used to determine the expression levels of netrin-1 and UNC5B. We made use of the agonist of PKCα (phorbol-12-myristate 13-acetate-PMA) and the inhibitor of PKCα (calphostin C) to treat renal cell carcinoma (RCC) cells, and MTT assays were used to measure cell proliferation. By immunofluorescence, we identified the localization of netrin-1 and UNC5B in RCC cell lines 769-P and ACHN. The expression of UNC5B in tumor tissues was significantly downregulated compared to the corresponding normal tissues in which netrin-1 was upregulated. In low grade tumors, UNC5B expression was more prominent while netrin-1 expression was the opposite when compared with high grade ones. Proliferation of ACHN cells was concentration dependent in the presence of PMA and calphostin C. Netrin-1 and UNC5B expressions were upregulated in cells treated with PMA while calphostin C reversed this upregulation. By immunofluorescence, we identified that netrin-1 was highly expressed in the nuclear but none of UNC5B. Our data highly suggested that PMA-induced upregulation and calphostin C-induced reversion of netrin-1 and UNC5B in kidney carcinoma were accompanied by the activation of the netrin-1/UNC5B pathways.