Abstract 826: SCL8A1 negatively regulated by miR-223 is one candidate for sodium/calcium transportation and low level of apoptosis in penile carcinomas.
Authors: Muñoz Juan J. , Drigo Sandra A. , Barros Mateus C. , Marchi Fábio , Soares Fernando A. , Pessoa Gustavo , Pessoa Gustavo , Vassallo José , Arruda Marco A. , Rogatto Silvia R. 
Published: August 2014

Background: Penile cancer (PeCa) is a rare disease in developed countries, but with high incidence in South America and Africa. Surgery is frequently used for local control of the disease and can lead to partial or complete amputation of the organ. Integrative analysis of large-scale gene expression and genomic alterations in PeCa showed down-expression of the solute carrier family 8 (SLC8A1, sodium/calcium exchanger) with no genomic changes suggesting that other mechanisms, such as micro-RNAs, could be involved in gene regulation. Intracellular Ca2+ can contribute to cancer cell proliferation and tumor progression, but can also induce tumor apoptosis by calcium-regulated cell death pathways. Therefore, we speculated if the down-expression of SLC8A1 mediated, at least in part, by miR-223 in penile carcinomas could lead to a reduction of cellular calcium levels and apoptosis suppression and to contribute for increased cell proliferation.

Aim: This study aimed to confirm the gene expression patterns of SLC8A1 and miR-223 in PeCa and normal tissues and to evaluate calcium levels and apoptosis in in a subset of the samples showing these alterations.

Methods: RNA was obtained from 39 fresh PeCa and 4 normal penile tissues. SLC8A1 gene and miRNA-223 transcript levels were evaluated by RT-qPCR. Fresh PeCa (n=2) matched with adjacent (n=1) and normal tissue from autopsy (n=1) showing alterations of SLC8A1 and miRNA-233 were selected and evaluated for calcium distribution by Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS). Caspase-3 and Ki-67 were evaluated by immunohistochemistry in 9 selected PeCa.

Results: Significant down-expression of SLC8A1 (P=0.010) and overexpression of miR-223 (P=0.0072) was detected in tumors in the comparison with normal controls. A significant negative correlation was detected between SLC8A1 transcript levels and miR-223 (P=0.015, r = -0.482), suggesting that this gene is regulated by this miRNA. LA-ICP-MS mapping revealed decreased calcium levels in tumor cells compared with adjacent normal cells and also compared with a normal tissue. Penile carcinoma tissue showed lower calcium counts (Ca44/C13 ratio=5,14 +/- 0,81) compared with normal tissues (Ca44/C13 ratio=6,34 +/- 4,63). In addition, PeCa presented considerably higher sodium counts (counts per second = 6.5 x 10ˆ5) compared with normal tissues (counts per second = 4 x 10ˆ5). Decreased caspase-3 and increased Ki-67 levels were detected in tumor tissues, indicating that low-level apoptosis and high cell proliferation index occurred in these samples.

Conclusions: The results suggested that down-regulation of SLC8A1 gene probably mediated by miR-223 can contribute to calcium levels reduction in PeCa and consequently in apoptosis suppression of these cells. Further functional studies are needed to prove this hypothesis.

Citation Format: Juan J. Muñoz, Sandra A. Drigo, Mateus C. Barros, Fábio Marchi, Fernando A. Soares, Gustavo Pessoa, Gustavo Pessoa, José Vassallo, Marco A. Arruda, Silvia R. Rogatto. SCL8A1 negatively regulated by miR-223 is one candidate for sodium/calcium transportation and low level of apoptosis in penile carcinomas. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 826. doi:10.1158/1538-7445.AM2013-826