Targeting the transcription factor c-Jun in cervical cancer cells

Abstract

Despite the development of vaccines for human papillomaviruses (HPV) in cervical cancer and other efforts to improve therapy, deaths still average 275,000 annually worldwide, with most women succumbing to recurrent or metastatic disease. The c-Jun oncogene is a subunit of the activating protein-1 (AP-1) transcription factor and is strongly expressed in cervical cancer, regulating the expression of HPV16 and 18 genes. AP-1 plays a major role in cell growth, migration and apoptosis in many cell types. This work examined the role of c-Jun in modulating cervical cancer cell line (HeLa) proliferation, migration, apoptosis, invasion, susceptibility to cisplatin and the underlying mechanisms.

c-Jun protein and mRNA levels were reduced by c-Jun siRNA. c-Jun silencing inhibited cell proliferation. Significantly, c-Jun suppression dramatically reduced HeLa migration and invasion and targeted down-regulation of cyclooxygenase-2 (Cox-2), intracellular adhesion molecule 1 (ICAM-1), matrix metalloproteinases (MMP)-1 and -9 genes highly expressed in cervical cancer and associated with metastatic growth. siRNA knockdown of Cox-2 also reduced HeLa migration and invasion as well as MMP-1 expression suggesting an intermediary link. In transfected cells over-expressing c-Jun, cell proliferation was not significantly increased but cell invasiveness was markedly enhanced in parallel with enhanced Cox-2 and MMP-1 expression as well as MMP-2 activity. Modulation of c-Jun expression did not synergistically combine with cisplatin to increase the susceptibility of HeLa cells to apoptosis or cell cycle disruption. In vivo, c-Jun siRNA pre-transfected HeLa-luc solid tumor growth and size were significantly retarded compared to the control groups.

siRNA targeting another transcription factor, Early Growth Response-1 (Egr-1) demonstrated significant inhibition of HeLa cell migration and invasion as well as reduced MMP-1 expression and MMP-9 activity, with concomitant blockade of c-Jun and Cox-2 expression, suggesting pivotal link of these genes to HeLa cell migration and invasion.

Reduced invasion potential of HeLa cells after c-Jun, Egr-1 and Cox-2 knockdown, respectively suggests the potential of these genes as targets in treatment of metastatic and recurrent cervical cancer. Data also suggest a mechanism involving c-Jun, Egr-1 and Cox-2 in the regulation of MMP-1.