This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Liao, Y.-H. Articles by Huang, P.-H. Search for Related Content PubMed PubMed Citation Articles by Liao, Y.-H. Articles by Huang, P.-H.

ARMS Depletion Facilitates UV Irradiation–Induced Apoptotic Cell Death in Melanoma

¹ Graduate Institute of Pathology, College of Medicine, National Taiwan University and Departments of ² Dermatology and ³ Pathology, National Taiwan University Hospital, Taipei, Taiwan

Requests for reprints: Pei-Hsin Huang, Graduate Institute of Pathology, College of Medicine, National Taiwan University, Chung-Shan South Road, No. 7, Taipei 100, Taiwan. Phone: 886-2-2312-3456, ext. 6677; Fax: 886-2-2393-4177; E-mail: phhuang{at}ntu.edu.tw.

Tumor cells often aberrantly reexpress molecules that mediate proper embryonic development for advantageous growth or survival. Here, we report that ankyrin repeat-rich membrane spanning (ARMS), a transmembrane protein abundant in the developing and adult neural tissues, is overexpressed in melanoma, a tumor ontogenetically originating from neural crest. Immunohistochemical study of 79 melanocytic lesions showed significantly increased expression of ARMS in primary malignant melanomas (92.9%) and metastatic melanoma (60.0%) in comparison with benign nevocellular nevi (26.7%). To investigate the role of ARMS in melanoma formation, murine B16F0 melanoma cells with stable knockdown of ARMS were established by RNA interference. Down-regulation of ARMS resulted in significant inhibition of anchorage-independent growth in soft agar and restrictive growth of melanoma in severe combined immunodeficient mice. Importantly, depletion of ARMS facilitated UVB-induced apoptosis in melanoma cells through inactivation of mitogen-activated protein kinase/extracellular signal–regulated kinase (ERK) kinase (MEK)/ERK. Addition of MEK inhibitor PD98059 further sensitized ARMS-depleted melanoma cells to UVB-induced apoptosis, whereas constitutively active MEK rescued ARMS-depleted cells from apoptosis. We further showed that BRAF, a downstream signaling molecule of ARMS in ERK pathway, is not mutated as a constitutively active form in acral lentiginous melanoma; in contrast, BRAF^T1799A mutation, which leads to constitutive activation of ERK signaling, was detected in 57.1% of superficial spreading melanoma. Our study suggests that overexpression of ARMS per se serves as one mechanism to promote melanoma formation by preventing stress-induced apoptotic death mediated by the MEK/ERK signaling pathway, especially in acral lentiginous melanoma, most of which does not harbor BRAF mutation. [Cancer Res 2007;67(24):11547–56]