Ovarian Cancer :: Differences between Low-Grade and High-Grade Ovarian Cancers

A new study suggests that ovarian tumors classified as serous borderline or low malignant potential (LMP) are not early precursors in the development of aggressive ovarian cancer, but may instead be part of an entirely different class of tumors. Furthermore, genes that were identified in this study as being expressed, or active, in these different classes of tumors could help identify targets for more specific diagnostics and therapies to treat this disease.

LMP is different than serous high-grade ovarian tumors (more aggressive tumors) yet shares remarkable similarities with serous low-grade ovarian tumors (less aggressive tumors). Both serous high-grade and low-grade ovarian tumors are types of invasive ovarian cancer. Whether serous LMP tumors can give rise to invasive ovarian cancers has been controversial.

The results of this study, which was conducted by a research team that included scientists from the National Cancer Institute (NCI), part of the National Institutes of Health, the Dana-Farber Cancer Institute, Boston, Mass., and the M.D. Anderson Cancer Center, Houston, Texas, appears in the November 15, 2005, issue of Cancer Research*. The study was supported by a Specialized Program of Research Excellence (SPORE) grant from the NCI. The research teams from the Dana-Farber Cancer Institute and M.D. Anderson Cancer Center are SPORE grant recipients.

Using a gene expression technique that reveals which genes are turned on or off in a cell, the researchers identified distinct differences between the gene expression profiles of LMP tumors and high-grade ovarian malignancies. The gene expression results suggested that serous low-grade ovarian tumors are more similar to LMP tumors than to serous high-grade ovarian cancers and that different biochemical pathways may be involved in the development of LMP and low-grade tumors compared to high-grade tumors.

Patients with serous low-grade or high-grade ovarian tumors currently receive the same treatment, which is surgery followed by chemotherapy. However, the finding that low-grade tumors are more similar to LMP tumors has significant therapeutic implications, said Michael Birrer, M.D., Ph.D., study leader and head, Molecular Mechanism Section at NCI.

Women with low-grade invasive tumors may benefit from therapies that are different from those given to patients with high-grade tumors. Furthermore, the biochemical pathways identified in this study may provide targets for more rational therapies for these different tumor types.

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