The Parkinson's disease (PD) associated protein, alpha-synuclein (alpha-syn/SNCA, is highly expressed in aggressive melanomas, which raises the possibility that alpha-syn has a pro-survival function in melanoma. Herein, we asked whether alpha-syn modulates the expression of the pro-oncogenic adhesion molecules L1CAM and N-cadherin. We used two human melanoma cell lines (SK-MEL-28, SK-MEL-29), SNCA-knockout (KO) clones, and two human SH-SY5Y neuroblastoma cell lines. In the melanoma lines, loss of alpha-syn expression resulted in significant decreases in the expression of L1CAM and N-cadherin and concomitant significant decreases in motility. On average, there was a 75% reduction in motility in the four SNCA-KOs compared to control cells. Strikingly, comparing neuroblastoma SH-SY5Y cells that have no detectable alpha-syn to SH-SY5Y cells that stably express & alpha-syn (SH/+alphaS), we found that expressing alpha-syn increased L1CAM and single-cell motility by 54% and 597%, respectively. The reduction in L1CAM level in SNCA-KO clones was not due to a transcriptional effect, rather we found that L1CAM is more efficiently degraded in the lysosome in SNCA-KO clones than in control cells. We propose that alpha-syn is pro-survival to melanoma (and possibly neuroblastoma) because it promotes the intracellular trafficking of L1CAM.

The Parkinson’s disease (PD) associated protein, alpha-synuclein (α-syn/SNCA), is highly expressed in aggressive melanomas. The goal of this study was to reveal possible mechanism(s) of α-syn involvement in melanoma pathogenesis. Herein, we asked whether α-syn modulates the expression of the pro-oncogenic adhesion molecules L1CAM and N-cadherin. We used two human melanoma cell lines (SK-MEL-28, SK-MEL-29), SNCA-knockout (KO) clones, and two human SH-SY5Y neuroblastoma cell lines. In the melanoma lines, loss of α-syn expression resulted in significant decreases in the expression of L1CAM and N-cadherin and concomitant significant decreases in motility. On average, there was a 75% reduction in motility in the four SNCA-KOs tested compared to control cells. Strikingly, comparing neuroblastoma SH-SY5Y cells that have no detectable α-syn to SH-SY5Y cells that stably express α-syn (SH/+αS), we found that expressing α-syn increased L1CAM and single-cell motility by 54% and 597%, respectively. The reduction in L1CAM level in SNCA-KO clones was not due to a transcriptional effect, rather we found that L1CAM is more efficiently degraded in the lysosome in SNCA-KO clones than in control cells. We propose that α-syn is pro-survival to melanoma (and possibly neuroblastoma) because it promotes the intracellular trafficking of L1CAM to the plasma membrane.

Malignant melanoma is one of the most aggressive and fifth most prevalent cancer among men and women. Clinical and epidemiological studies shows that Parkinson’s disease (PD) patients have higher risk of developing invasive melanoma, and, reciprocally, patients with invasive melanoma have a higher risk of developing PD. Alpha-synuclein (α-syn; SNCA), an intrinsically disordered protein expressed in neurons, is also highly expressed in malignant melanoma and is a common molecular signature between Parkinson’s disease and melanoma. We have previously reported that SK-Mel-28 SNCA-knockout (KO) cells exhibit suppressed tumor growth and proliferation in vivo and in vitro, and that putting back SNCA via lenti virus restored the phenotype to that of the control cells. The present study is designed to investigate the role of α-syn in melanoma progression in SK-MEL-28 cells in the context of metastasis and the epithelial-to-mesenchymal transition (EMT). The SK-Mel-28 SNCA-KO clones showed a significant decrease in the cell-surface protein L1CAM, a major cell adhesion molecule highly expressed in various melanoma and correlates with melanoma progression, whereas the knock in clones resembled the control. Migration and invasion assay were performed using transwell chambers showed a profound migratory and invasive defect in SNCA-KO clones. To explore further whether this is a proliferative or migratory defect, a single cell phagokinetic motility assay was performed with colloidal gold which showed a marked decrease in cell motility in knockout clones compared to control and knock in clones, which was consistent with our migration and invasion experiments. To determine the proteins involved in the inhibition of invasion mediated by α-syn, we immunoblotted for the mesenchymal markers N-cadherin and vimentin, and these were significantly downregulated in the SNCA-KO clones. These data reinforce that knocking out SNCA impedes melanoma cell migration and invasion in SK-Mel- 28 cell line, implying that α-syn might be a novel therapeutic target for malignant melanoma. Citation Format: Nithya Gajendran, Santhanasabapathy Rajasekaran, Nirjhar M. Aloy, Sahar Shekoohi, Stephan N. Witt. Knocking out SNCA in SKMEL28 melanoma cells suppresses EMT and prevents invasion [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2443.