The Vav3 oncogene enhances the malignant potential of prostate cancer cells under chronic hypoxia

Abstract

Objectives: We had previously reported that chronic hypoxia induces androgen-independent growth in the human prostate cancer cell line LNCaP. In this study, we have identified a key molecule, the Vav3 oncogene, and investigated the effects of Vav3 overexpression on cancer cell growth and malignant behavior and the possible apoptosis-inducing effect of Vav3 expression knockdown by small interfering ribonucleic acid (siRNA) in LNCaP cells under chronic hypoxia (LNCaP/CH).

Methods and materials: Hypoxia-inducible oncogenes were identified by complementary deoxyribonucleic acid (cDNA) microarray and Ingenuity Pathway Analysis in order to investigate gene ontology and functional pathways and networks. siRNA was used to knockdown the Vav3 target gene and analyze the effects on proliferation, invasion, migration, and apoptosis of LNCaP/CH cells. Vav3 cDNA was transfected into LNCaP cells under normoxia (LNCaP/N) to establish Vav3-overexpressing clonal cell lines, whose proliferation, invasion, and migration was then examined. Immunoblot analysis was used to investigate the activation of Akt, a Vav3 downstream target molecule.

Results: cDNA microarray analysis and Ingenuity Pathway Analysis identified Vav3 as a hypoxia-inducible oncogene that was highly associated with malignant behavior. Vav3 messenger RNA and protein expression in LNCaP/CH cells were higher than in LNCaP/N and LNCaP cells cultured under acute hypoxia (LNCaP/AH). The growth rate of LNCaP/CH cells was lower than that of LNCaP/N cells but higher than that of LNCaP/AH cells. LNCaP/CH cells showed higher invasion and migration than LNCaP/N and LNCaP/AH cells. Interrupting Vav3 expression strongly suppressed the proliferation, invasion, and migration of LNCaP/CH cells. Furthermore, siRNA led to apoptosis with increased caspase-3 and cleaved poly (adenosine diphosphate-ribose) polymerase activation in LNCaP/CH cells. Stable Vav3 overexpression in LNCaP cells promoted cell proliferation, invasion, and migration with Akt activation.

Conclusions: Our results demonstrate that Vav3 plays a crucial role in prostate cancer growth and malignant behavior, thus revealing a novel potential therapeutic target.

Keywords: Chronic hypoxia; Prostate cancer; Vav3.