Immunohistochemical analysis of suprabasin, isthmin-1 and podocalyxin immunoreactivity in malignant melanoma and melanocytic nevus

This study aimed to immunohistochemically examine the immünoreactivity of suprabasin (SBSN), isthmin-1 (ISM-1), and podocalyxin (PODXL) in tissue samples taken from patients with malignant malign melanoma and melanocytic nevi. A total of 60 skin samples were used, including 20 skin samples diagnosed as melanocytic nevüs, 20 as malignant malign melanoma, and 20 healthy skin (taken adjacent to diseased skin but showing no pathology) as the control group. Skin samples from patients diagnosed with other dermatological diseases, malignancies, or diabetes mellitus were excluded. Following confirmation of diagnoses, 5–6 µm thick sections were taken from paraffin blocks for indirect immunohistochemical staining using antibodies for PODXL, ISM, and SBSN. In this method, tissues incubated with primary antibodies in a moist environment were treated with biotinylated secondary antibodies and further incubated with enzyme-conjugated streptavidin (peroxidase or alkaline phosphatase), followed by application of the chromogens 3-Amino-9-Ethylcarbazole (AEC) or 3,3'-diaminobenzidine (DAB). A histoscore was created based on the extent of immunoreactivity (0.1: <25%, 0.4: 26–50%, 0.6: 51–75%, 0.9: 76–100%) and intensity (0: none, +0.5: very low, +1: low, +2: moderate, +3: strong). The formula used was: histoscore = extent × intensity. The data were analyzed using the Statistical Package for the Social Sciences (SPSS, version 22.0; Chicago, IL, USA). Kolmogorov-Smirnov and Shapiro-Wilk tests were used for normality, followed by independent samples t-test for comparisons between two groups, and ANOVA for comparisons among more than two groups. A p-value of <0.05 was considered statistically significant. In this study, immunohistochemical examination of SBSN immunoreactivity revealed a statistically significant decrease in the malign melanoma group compared to the control group (p=0.025), while a significant increase was observed in the melanocytic nevus group (p<0.001). Additionally, a statistically significant increase in SBSN immunoreactivity was found in the melanocytic nevus group compared to the malignant malign melanoma group (p<0.001). For ISM-1 immunoreactivity, a significant decrease was observed in the malign melanoma group compared to the control group (p=0.031), while a significant increase was observed in the melanocytic nevus group (p<0.001). Furthermore, ISM-1 immunoreactivity was significantly higher in the melanocytic nevus group compared to the malign melanoma group (p<0.001). Regarding PODXL immunoreactivity, both malign melanoma and melanocytic nevus groups showed a statistically significant increase compared to the control group (p<0.001). In conclusion, PODXL was significantly elevated in the malign melanoma group, whereas ISM-1 and SBSN levels were significantly reduced. It is suggested that PODXL may contribute to malign melanoma development through the MAPK pathway, PI3K, and BRAF mutations. However, the inability to measure the ezrin protein, which could mediate these pathways and mutations, is a limitation of the study. ISM-1 is known for its anti-apoptotic and anti-angiogenic properties, and its reduction in this study may support proliferation and angiogenesis, contributing to malign melanoma cell growth and migration. The decrease in SBSN may be attributed to its expression mainly in keratinocyte cells and the still poorly understood molecular mechanisms. Further studies on these molecules could contribute to a better understanding of their mechanisms.