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RhoC May Be a Marker for Small, Aggressive Breast Cancers

RhoC May Be a Marker for Small, Aggressive Breast Cancers

SAN FRANCISCO—Complete axillary lymph node dissection followed by
chemotherapy is standard treatment for larger breast tumors, but it is less
frequently performed when the tumor is smaller than 1 cm. Still, approximately
5% to 8% of these small breast tumors are very aggressive. Currently, there is
no way to identify which of these small tumors are more likely to metastasize
and thus should receive more appropriate treatment.

Now, early research presented at the 93rd Annual Meeting of the American
Association for Cancer Research (abstract 3548) indicates that the protein
RhoC-GTPase (RhoC) may be a marker for these small, aggressive breast cancers.
Other studies have previously indicated that RhoC, which is involved in cell
polarity and motility, may be overexpressed in cancers of the breast, pancreas,
and skin.

Building on their previous studies of the usefulness of RhoC as a marker for
inflammatory breast cancer, the University of Michigan researchers developed a
specific polyclonal anti-RhoC antibody test that they then used on 182 breast
tissue samples from 164 patients, obtained from the University of Michigan’s
breast cancer library. Vascular smooth muscle cells were used as internal
positive controls.

Staining intensity following immunohistochemistry on formalin-fixed tissues
was rated from 0 to 3, with a rating of 0-1 considered negative and a rating of
2-3 positive.

RhoC was expressed in 32% of the invasive carcinomas, but in none of the
normal breast, fibrocystic breast, atypical hyperplasia, or ductal carcinoma in
situ samples, said Celina Kleer, MD, assistant professor of pathology,
University of Michigan Medical School, Ann Arbor. Specificity for tumors with metastatic potential was 88%, and it was 92%
for invasive tumors smaller than 1 cm that had metastasized.

Dr. Kleer noted that RhoC expression was associated with negative
progesterone receptors and HER-2/neu overexpression, two other markers
associated with a poor prognosis.

Clinical Test for RhoC a Possibility

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