Emerging evidences have shown the correlation of autophagy with tumor progression, so that impaired or inhibition of autophagy leads to tumorgenisity. Howeverdifferent results of autophagy activity during tumorigenesis have been recorded to date [18]. Therefore, it is expected that autophagy activity is low in the early stages while elevated with tumor progression. However, several experiment in melanoma or even other tumors reported controversial results. For instance, Beclin1 act as a haploinsufficient tumour-suppressor gene and can be either monoallelically deleted or display reduced expression in breast, ovarian, and prostatic cancer [19]. In contrast, other reports displayed that the overexpression of Beclin 1 correlated with tumorigenesis incolorectal and gastric cancer [20]. In cutaneous malignant melanomas, the results showed that Beclin 1 significantly decreased with tumor progression [21, 22]. In current experiment,Beclin1 gene expression was reduced in melanoma patients in compare to tumor margins (P < 0.0001). However, the evaluation of Beclin1 level in all stages showed the decreased level in stage 1 and then went up as the tumor progressed, suggesting the autophagy activity during melanoma progression or due to autophagy induction following by chemotherapy. This is agreement with the study of advanced malignant melanoma (MM) which showed overexpression of Beclin-1 in advanced malignant melanoma [23].
LC3 expression as another autophagy marker has been reported to be either decreased in brain and ovary cancer[24, 25] or increased in esophageal and gastrointestinal neoplasms [26]. LC3 expression was found associated with poor outcome in pancreatic cancer and with a better survival in glioblastoma patients with poor performance score[24, 27]. In cutaneousmelanocytic lesions LC3 significantly decreased with tumor progression and the lowest expression of LC3 II protein was observed in melanoma metastases [18]. While in another experiment with TMA in melanoma and breast has confirmed overexpression of LC3 II and the positive correlation with Ki-67 [5]. In our study, high level of LC3 II protein was observed in melanoma tumors in compare to tumor margins, suggesting autophagy activity during melanoma tumorigenesis.Overexpression of p62 is also observed in a number of cancers, including melanoma, and is a marker of poor prognosis. Indeed, increasing levels of p62 expression in early stage of melanoma followed by subsequent decreasing it, suggesting the novel independent prognostic biomarkers for early stage melanomas[28]. In current study and in line with previous studies, during the progression of tumor, the autophagy marker of p62 was decreased. Analyzing autophagy in tissues with few markers is very difficult due to the paradoxical function of autophagy in tissues. Therefore, it is better that the expression levels of LC3II and p62 markers be done in parallel with the ATG study [27].There are several reports about the ATG5 gene and protein expression in different cancers and especially in melanoma patients. Liu H et al in 2013 reported ATG5, is often down-regulated inprimary melanomas compared to benign nevi. They also checked LC3II, Beclin1 and p62 in a few cases. The results have shown that Beclin1 was indistinguishable between melanomasand benign nevi, a reducedexpression of LC3 and increased expression of p62 was observed[29].In current experiment, the autophagy markers in different stages of melanoma was determined and revealed that although ATG5 was raised at early stage, the comparison of ATG5 expression in all melanoma tumors was decreased in compare with tumor margin (p < 0.05). Autophagy can protect tumor cells that are exposed to anticancer drugs, indicating the potential for inhibition of autophagy in cancer therapy[30].It has been shown that elevated autophagy in early stage is associated with invasiveness and drug resistance [31, 32]. Moreover, autophagy was induced in melanoma cells under situations of metastasis [33] and/or hypoxia[34].All these data propose thatautophagy may be increased in melanoma cells as an adaptive stressresponse to chemotherapy and/or metabolic stress. In such studies, thequantification of additional ATG proteins should also be considered. So, in addition to ATG5, Beclin 1 expression at mRNA level was evaluated and revealed that the alteration of expression was notobserved during tumor progression. However,its expression was decreased in all stages in compare with tumor margin (p < 0.0001), suggesting that the expression of ATG proteins is, at least partially, differentially regulated. Previously published work, however, had reported a down-regulation of Beclin 1 in association with melanoma disease progression [18].
In contrast to the previous reports, our experiment in all stages was reported the autophagy activity was observed during tumor progression.Although in early stage, a reduction of autophagy may promote tumor growth, by preventing senescence, In later stages, basal autophagy activity resumes or is induced, leading to chemoresistance. Indeed, the regulation of autophagy in tumorigenesisdepends on the stage of the tumors[29].
Furthermore, Beclin 1 and LC3II expression level during tumor progression positively correlated with melanoma ulceration whereas p62 protein expression was inversely correlated (n = 22). And were not significantly correlate with melanoma mitotic rate, thickness and specific siteswhereas previous study reported that in primary melanomas, melanoma thickness and ulceration were positively correlated with Beclin 1 expression and inversely correlatedwith cytoplasmic LC3 II protein expression.Melanoma mitotic rate wasinversely correlated with cytoplasmic LC3 protein expression [18], recommending more samples need to be analyzed.
Prognosis and survival for malignant melanoma is highly dependent on early diagnosis and treatment. Earlier experiments proposed p62, LC3 and Beclin 1 have been proposed as potential prognostic biomarkers for early stage of melanomas [35]. We also showed ATG5 and Beclin 1could be a reliable markers in early detection of melanoma.