Protein Kinase Cα (PKCα) Regulates p53 Localization and Melanoma Cell Survival Downstream of Integrin αv in Three-dimensional Collagen and in Vivo

Stephen D Smith,Martin Enge,Wenjie Bao,Minna Thullberg,Tânia D.F Costa,Helene Olofsson,Behxhet Gashi,Galina Selivanova,Staffan Strömblad

doi:10.1074/jbc.m112.341917

Abstract

Protein kinase C α (PKCα) is overexpressed in numerous types of cancer. Importantly, PKCα has been linked to metastasis of malignant melanoma in patients. However, it has been unclear how PKCα may be regulated and how it exerts its role in melanoma. Here, we identified a role for PKCα in melanoma cell survival in a three-dimensional collagen model mimicking the in vivo pathophysiology of the dermis. A pathway was identified that involved integrin αv-mediated up-regulation of PKCα and PKCα-dependent regulation of p53 localization, which was connected to melanoma cell survival. Melanoma survival and growth in three-dimensional microenvironments requires the expression of integrin αv, which acts to suppress p53 activity. Interestingly, microarray analysis revealed that PKCα was up-regulated by integrin αv in a three-dimensional microenvironment-dependent manner. Integrin αv was observed to promote a relocalization of endogenous p53 from the nucleus to the cytoplasm upon growth in three-dimensional collagen as well as in vivo, whereas stable knockdown of PKCα inhibited the integrin αv-mediated relocalization of p53. Importantly, knockdown of PKCα also promoted apoptosis in three-dimensional collagen and in vivo, resulting in reduced tumor growth. This indicates that PKCα constitutes a crucial component of the integrin αv-mediated pathway(s) that promote p53 relocalization and melanoma survival.

Highlights

Integrin ␣v promotes melanoma cell survival in in vivo and in vitro three-dimensional environments
Knockdown of PKC␣ promoted apoptosis in three-dimensional collagen and in vivo, resulting in reduced tumor growth. This indicates that PKC␣ constitutes a crucial component of the integrin ␣v-mediated pathway(s) that promote p53 relocalization and melanoma survival
The transcription of other genes was up-regulated in three-dimensional collagen upon lack of integrin ␣v expression, whereas some genes were down-regulated in an integrin ␣v and three-dimensional collagen-dependent manner

Summary

Background

Integrin ␣v promotes melanoma cell survival in in vivo and in vitro three-dimensional environments. Results: PKC␣ is up-regulated in an integrin ␣v- and three-dimensional collagen-dependent manner and promotes p53 relocalization and melanoma survival. We identified a role for PKC␣ in melanoma cell survival in a three-dimensional collagen model mimicking the in vivo pathophysiology of the dermis. Knockdown of PKC␣ promoted apoptosis in three-dimensional collagen and in vivo, resulting in reduced tumor growth This indicates that PKC␣ constitutes a crucial component of the integrin ␣v-mediated pathway(s) that promote p53 relocalization and melanoma survival. A recent yeast model identified PKC␣ as an inhibitor of p53-induced growth arrest [20] It has remained unclear how PKC␣ may be regulated and exert its role in malignant melanoma. PKC␣ knockdown inhibited integrin ␣v-mediated melanoma survival in three-dimensional collagen and in vivo tumor growth. Our results indicate that in melanoma, PKC␣ up-regulation is critical for integrin ␣v␤3mediated p53 regulation and suppression of apoptosis

EXPERIMENTAL PROCEDURES

RESULTS

DISCUSSION