Analysis of APAF‐1 expression in human cutaneous melanoma progression

Abstract

APAF-1 plays a pivotal role in mitochondria-dependent apoptosis, binding to cytochrome c and favoring activation of caspase-9. It has been shown that epigenetic silencing of the APAF-1 gene is a common event in several metastatic melanoma cells in vitro. We determined, by Western blot, variation in the level of expression of APAF-1 in several human melanoma cell lines and, by immunohistochemistry, in a group of 106 histological samples including benign and malignant melanocytic lesions. We observed APAF-1 down-regulation or loss of expression in two metastatic melanoma cell lines, compared to primary melanoma cell lines. The immunohistochemical analysis revealed a significant difference in APAF-1 staining between nevi and melanomas. In addition, we found a significant negative correlation between APAF-1 expression level and tumor thickness and between primary melanomas and metastases. We conclude that loss of APAF-1 expression can be considered as an indicator of malignant transformation in melanoma.

Apaf-1 expression in malignant melanoma

“…4,5 Moreover, our experiments correlating Apaf-1 expression with chemosensitivity were conducted blindlyone laboratory (YL) measured Apaf-1 expression and the other (SWL) assayed apoptosis and the results were compared later. Finally, we confirmed the immunoblotting results by Northern blotting and in situ hybridization 1 and, more recently, other investigators corroborated our observations using three different antibodies, [6][7][8][9] and by LOH analyses and quantitative RT-PCR. 10,11 Given that technical issues are unlikely to account for the differences between data sets, it is possible that the studies by Peltenburg and Allen did not examine enough samples to make reliable conclusions.…”

“…11 Baldi et al, Dai et al, Zannon et al and Mustika et al report a heterogeneous expression of Apaf-1, highly positive in benign nevi but weak or undetectable in 35-50% in situ melanomas and lymph node and visceral metastases. [6][7][8][9] In addition, Qin et al have also independently reported low Apaf-1 expression in metastatic melanoma cell lines used in our initial study. 12 These results, along with recent reports of low Apaf-1 expression in other melanoma cell lines, 13 are consistent with our initial findings.…”

“…This would not be surprising, as melanoma is notorious for its heterogeneity 7 and, accordingly, such discrepancies have been reported before. For example, BRAF was originally found mutated in 66% of malignant melanomas, but subsequently rates varying from 0 to 100% have been observed depending on the anatomical site and association with sun exposure.…”

Reduced Apaf-1 expression in human cutaneous melanomas

“…Contrarily, Baldi et al (2004) reported that reduced Apaf-1 expression correlated with melanoma thickness. The following reasons may result in the discrepancy between our results and those by Baldi et al: (1) different antibodies used for immunohistochemical staining; and (2) different technical approaches for immunohistochemisty.…”

Apaf1 apoptotic function critically limits Sonic hedgehog signaling during craniofacial development

“…[38][39] This finding makes the Apaf1 yautja allele unique compared with existing targeted Apaf1 mutant alleles, which all lack protein expression. [18][19][20] We next examined the susceptibility of Apaf1 yautja MEFs to apoptotic stimuli.…”