Protein expression patterns in primary carcinoma of the vagina

Abstract

Protein patterns in six samples from primary vaginal cancers, in five from normal vaginal tissue and in five primary cervical cancers, were analysed using two-dimensional polyacrylamide gel electrophoresis (2-DE). Protein expression profile was evaluated by computer-assisted image analysis (PDQUEST) and proteins were subsequently identified using matrix-assisted laser desorption/ionisation mass spectrometry. The aim was to analyse the protein expression profiles using the hierarchical clustering method in vaginal carcinoma and to compare them with the protein pattern in cervical carcinoma in order to find a helpful tool for correct classification and for increased biomedical knowledge. Protein expression data of a distinct set of 33 protein spots were differentially expressed. These differences were statistically significant (Mann-Whitney signed-Ranked Test, P<0.05) between normal tissue, vaginal and cervical cancer. Furthermore, protein profiles of pairs of primary vaginal and cervical cancers were found to be very similar. Some of the protein spots that have so far been identified include Tropomyosin 1, cytokeratin 5, 15 and 17, Apolipoprotein A1, Annexin V, Glutathione-S-transferase. Others are the stress-related proteins, calreticulin, HSP 27 and HSP 70. We conclude that cluster analysis of proteomics data allows accurate discrimination between normal vaginal mucosa, primary vaginal and primary cervical cancer. However, vaginal and cervical carcinomas also appear to be relatively homogeneous in their gene expression, indicating similar carcinogenic pathways. There might, further, be a possibility to identify tumour-specific markers among the proteins that are differentially expressed. The results from this study have to be confirmed by more comprehensive studies in the future.

Figure 1

(A–C) Representative examples of 2-DE gels derived from a normal vagina, primary vaginal cancer and primary cancer of the cervix. Whole-cell lysate was subjected to 2-DE using IPG strips pH 4–7 in the first and 10–13% SDS polyacrylamide gel in the second dimension. Marked are some of the identified proteins: HSP (heat shock proteins), TM (Tropomyosin), CK (Cytokeratin), GST (glutathione-S-transferase).

Figure 2

Global analysis of normal vaginal tissue, vaginal cancer and cervical cancer samples using expression data set from 33 polypeptides. Expression levels in all the samples are measured as ppm. Blue=normal, red=vaginal cancer and green=cervical cancer.

Figure 3

(A) Cluster analysis of normal, vaginal cancer and cervical cancer samples using expression data set from 33 polypeptides. (B) Correspondence analysis plot of same data set; Blue=normal, red=vaginal cancer and green=cervical cancer.

Figure 4

(A) Cluster analysis of normal, vaginal cancer and cervical cancer samples using expression data set from 23 polypeptides. (B) Correspondence analysis plot of same data set; Blue=normal, red=vaginal cancer and green=cervical cancer.