Discrimination between uterine serous papillary carcinomas and ovarian serous papillary tumours by gene expression profiling

Abstract

High-grade ovarian serous papillary cancer (OSPC) and uterine serous papillary carcinoma (USPC) represent two histologically similar malignancies characterised by markedly different biological behavior and response to chemotherapy. Understanding the molecular basis of these differences may significantly refine differential diagnosis and management, and may lead to the development of novel, more specific and more effective treatment modalities for OSPC and USPC. We used an oligonucleotide microarray with probe sets complementary to >10 000 human genes to determine whether patterns of gene expression may differentiate OSPC from USPC. Hierarchical cluster analysis of gene expression in OSPC and USPC identified 116 genes that exhibited >two-fold differences (P<0.05) and that readily distinguished OSPC from USPC. Plasminogen activator inhibitor (PAI-2) was the most highly overexpressed gene in OSPC when compared to USPC, while c-erbB2 was the most strikingly overexpressed gene in USPC when compared to OSPC. Overexpression of the c-erbB2 gene and its expression product (i.e., HER-2/neu receptor) was validated by quantitative RT-PCR as well as by flow cytometry on primary USPC and OSPC, respectively. Immunohistochemical staining of serous tumour samples from which primary OSPC and USPC cultures were derived as well as from an independent set of 20 clinical tissue samples (i.e., 10 OSPC and 10 USPC) further confirmed HER-2/neu as a novel molecular diagnostic and therapeutic marker for USPC. Gene expression fingerprints have the potential to predict the anatomical site of tumour origin and readily identify the biologically more aggressive USPC from OSPC. A therapeutic strategy targeting HER-2/neu may be beneficial in patients harbouring chemotherapy-resistant USPC.

Figure 1

Molecular profile of 11 primary OSPC and USPC cell lines. Hierarchical clustering of 59 genes with differential expression between six OSPC and five USPC groups (P<0.05) using a two-fold threshold. The cluster is colour coded using red for upregulation, green for downregulation and black for median expression. Agglomerative clustering of genes was illustrated with dendrograms. The symbol for each gene corresponding to the oligonucleotide spotted on the array is shown.

Figure 2

Molecular profile of primary OSPC and USPC cell lines. Hierarchical clustering of 116 genes with differential expression between five OSPC and five USPC groups (P<0.05) using a two-fold threshold. The cluster is colour coded using red for upregulation, green for downregulation and black for median expression. Agglomerative clustering of genes was illustrated with dendrograms. The symbol for each gene corresponding to the oligonucleotide spotted on the array is shown. USPC upregulated genes are shown in red ink while OSPC upregulated genes are shown in blue ink.

Figure 3

Quantitative RT – PCR and microarray expression analysis of PAI-2 (SERPINB2) and c-erbB2 (ERBB2) selected genes differentially expressed between OSPC and USPC.

Figure 4

FACS analysis of Herceptin staining of three primary OSPC and three USPC cell lines. Data with Herceptin are shown in solid black while isotype control MAb profiles are shown in white. HER-2/neu expression was significantly higher on USPC cell lines compared to OSPC cell lines (P<0.001 by Student's t-test).

Figure 5

Immunohistochemical staining for HER-2/neu expression on three paraffin-embedded OSPC3 and three USPC5 specimens from which primary cell lines have been established. OSPC1, OSPC3 and OSPC5 (left panel) showed negative or light (1+) staining for HER-2/neu. USPC3, USPC4 and USPC5 (right panel), showed heavy (3+) staining for HER-2/neu. Original magnification × 400.