ROCK1 as a novel prognostic marker in vulvar cancer

Background

Vulvar carcinoma is an infrequent tumour, accounting for fewer than 3% of all malignant tumours that affect women, but its incidence is rising in the past few decades. In young women, the manifestation of the vulvar carcinoma is often linked to risk factors such as smoking and HPV infection, but most cases develop in women aged over 50 years through poorly understood genetic mechanisms. Rho-associated coiled-coil-containing protein kinase 1 (ROCK1) has been implicated in many cellular processes, but its function in vulvar cancer has never been examined. In this study, we aimed to determine the prognostic value of ROCK1 gene and protein analysis in vulvar squamous cell carcinoma (VSCC).

Methods

ROCK1 expression levels were measured in 16 vulvar tumour samples and adjacent normal tissue by qRT-PCR. Further, 96 VSCC samples were examined by immunohistochemistry (IHC) to confirm the involvement of ROCK1 in the disease. The molecular and pathological results were correlated with the clinical data of the patients. Sixteen fresh VSCC samples were analyzed by array-based comparative genomic hybridization (aCGH).

Results

In each pair of samples, ROCK1 levels were higher by qRT-PCR in normal tissue compared with the tumour samples (p = 0.016). By IHC, 100% of invasive front areas of the tumour and 95.8% of central tumour areas were positive for ROCK1. Greater expression of ROCK1 was associated with the absence of lymph node metastasis (p = 0.022) and a lower depth of invasion (p = 0.002). In addition, higher ROCK1 levels correlated with greater recurrence-free survival (p = 0.001). Loss of ROCK1 was independently linked to worse cancer-specific survival (p = 0.0054) by multivariate analysis. This finding was validated by IHC, which demonstrated enhanced protein expression in normal versus tumour tissue (p < 0.001). By aCGH, 42.9% of samples showed a gain in copy number of the ROCK1 gene.

Conclusions

ROCK1 is lower expressed in tumour tissue when compared with adjacent normal vulvar epithelia. In an independent sample set of VSCCs, lower expression levels of ROCK1 correlated with worse survival rates and a poor prognosis. These findings provide important information for the clinical management of vulvar cancer.

Abstract 3427: Uncovering vulvar cancer: Integrated analysis of genomic and transcriptomic data

Vulvar squamous cell carcinoma (VSCC) is a rare gynecological cancer, representing approximately 3-5% of genital tumors. However, its incidence has risen considerably and no consistent profile of this disease was established so far. Also, little is known about the genomic abnormalities of VSCC and how they correlate with gene expression. In order to verify which are the major genomic alterations that lead to gene expression abnormalities we used integrative analysis in VSCC samples. Seventeen frozen samples of VSCC were carried out in genome-wide expression (GWE) profiling using the Agilent Whole Human Genome Microarray 60K (Agilent Technologies, Santa Clara, CA, USA) and in Array-CGH (aCGH) using the Agilent Human Genome CGH Microarray 60K (Agilent Technologies, Santa Clara, CA, USA) following the manufacturer's protocol. Data were extracted and flagged with Feature Extraction version 10.5 (Agilent Technologies, Santa Clara, CA) and the aCGH data was processed using NEXUS 6.0 (BioDiscovery, Hawthorne, CA, USA). JISTIC was used to classify genes mapped at gains and losses in genomic regions. Differentially expressed genes were identified by SAM statistical test. The CONEXIC algorithm was applied to integrate the data and in silico functional analysis were performed using Ingenuity Pathways Analysis (IPA) (Ingenuity® Systems). The aCGH analysis revealed 216 significant genomic alterations including 196 gains and 20 losses. GWE profile identified 3799 differentially expressed genes in comparison with normal tissue including 1352 up-regulated and 2447 down-regulated. The integrated analysis showed that genomic and transcriptomic results were concordant in 47 genes, in which 46 were up regulated and involved in gain of DNA copy number and only 1 gene (PLXDC2) was down-regulated and associated to genomic loss. According to IPA analysis of the top biological functions associated with the 47 genes, 3 of them were related with “tumor morphology”. Also, “cell death and survival” and “cellular function and maintenance” were included in the list of pathways disrupted by the genes selected as possible drivers of VSCC. Three significant networks could be defined comprising these genes. The first network comprised 18 of the concordant genes and was associated to functions as carbohydrate metabolism, small molecule biochemistry, cellular function and maintenance. The second network (18 genes) was related to RNA post-transcriptional modification, developmental disorder and hereditary disorder. The third network (15 genes) was associated to RNA post-transcriptional modification, gene expression and organ development. Thereby, important signaling networks were found disrupted by these genes which could influence tumor development or progression in VSCC. Therefore, these genes might be useful as a first step to identify molecular markers to improve diagnosis and therapeutic approaches for this tumor.

Citation Format: André M. Lavorato-Rocha, Beatriz de Melo Maia, Iara S. Rodrigues, Fabio A. Marchi, Gabriel R. Fernandes, Glauco Baiocchi, Fernando A. Soares, Silvia R. Rogatto, Yukie Sato-Kuwabara, Rafael M. Rocha. Uncovering vulvar cancer: Integrated analysis of genomic and transcriptomic data. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3427. doi:10.1158/1538-7445.AM2014-3427