Discrimination between serous low malignant potential and invasive epithelial ovarian tumors using molecular profiling

Abstract

Tumors of low malignant potential (LMP) represent 20% of epithelial ovarian cancers (EOCs) and are associated with a better prognosis than the invasive tumors (TOV). Defining the relationship between LMPs and TOVs remains an important goal towards understanding the molecular pathways that contribute to prognosis, as well as providing molecular markers, for these EOCs. To this end, DNA microarray analyses were performed either in a primary culture or a tumor tissue model system and selected candidate genes showing a distinctive expression profile between LMPs and TOVs were identified using a class prediction approach based on three statistical methods of analysis. Both model systems appear relevant as candidate genes identified by either model allowed the proper reclassification of samples as either LMPs or TOVs. Selected candidate genes (CAS, CCNE1, LGALS8, ITGb3, ATP1B1, FLIP, KRT7 and KRT19) were validated by real-time quantitative PCR analysis and show differential expression between LMPs and TOVs. Immunohistochemistry analyses showed that the two tumor classes were distinguishable by their expression of CAS, TNFR1A, FLIP, CKS1 and CCNE1. These results define signature patterns for gene expression of LMPs and TOVs and identify gene candidates that warrant further study to deepen our understanding of the biology of EOC.

Gene expression profiling of primary cultures of ovarian epithelial cells identifies novel molecular classifiers of ovarian cancer

“…Gene expression of epithelial ovarian cancer C Le Page et al Interestingly, our LMP tumours showed the least distinct profile in comparison to NOSE (Figure 1), which correlates with the weak aggressive potential of these tumours and the favourable prognostic for the patient. The present results correlate well with recent attempts to distinguish LMP and solid malignant tumours using a microarray and gene profiling approach (Gilks et al, 2005;Meinhold-Heerlein et al, 2005;Ouellet et al, 2005). Here, we detected only a very small set of genes differentially expressed in LMP tumours.…”

“…As previously described (Ouellet et al, 2005), RNA was linearly amplified by Alethia Biotherapeutics (Montreal, QC, Canada). The RAMP RNA produced is ( þ ) sense.…”

“…Experiments were performed in duplicate. Control RNA (Erk) was chosen based on stable expression in 69 ovarian samples containing normal and tumour types as previously described (Ouellet et al, 2005). Primers are described in Supplementary Table 2.…”

“…Interestingly, this classifier allowed a lower ratio of errors/correctly classified (r ¼ 0.05) than the set of 126 genes. To validate the classifier, an additional independent test set of 23 primary culture samples and 137 arrays of surgical specimens from publicly available data sets derived from Affymetrix HuFL GeneChip platform (Welsh et al, 2001;Schwartz et al, 2002;Ouellet et al, 2005) were tested. The set of 23 primary culture samples contained two LMP serous ascites.…”

“…NOSE cultures, derived by scraping the surface of the ovary, are highly homogenous and provide conditions in which normal cells replicate over a limited number of generations. In addition, a recent study comparing candidate genes able to stratify low-from high-malignancy tumours (identified in primary cultures and tumour tissues) showed that candidate genes identified in primary cultures were also able to reclassify samples derived from tumour tissues (Ouellet et al, 2005). Based on these advantages, we studied primary cultures enriched over several passages.…”