The insulinlike growth factor I receptor may offer a much-needed therapeutic target for triple-negative breast cancer, which can be notoriously hard to treat.
High levels of insulinlike growth factor I receptor (IGF-IR) expression appear to enhance survival or a subset of patients with this type of cancer, based on the results of a small study.
“In triple-negative breast cancer patients younger than 55, high expression is associated with longer survival,” Dr. Agneiszka W. Witkiewicz said during a press briefing sponsored by the American Association for Cancer Research (AACR).
Unlike hormone receptor– positive or HER2-positive breast cancers, triple-negative breast cancer has lacked a drug target and is managed with conventional chemotherapy. While triple-negative breast cancer accounts for only 15%-20% of breast cancer cases, it results in half of all breast cancer deaths, said Dr. Witkiewicz, a pathologist at Thomas Jefferson University in Philadelphia and an investigator on the study.
Tissue was evaluated from 99 women with triple-negative breast cancer. The samples were stained with anti-IGF-IR antibody (Ventana Medical Systems Inc.), and scored for IGF-IR protein expression according to standardized criteria originally developed to assess HER2 expression. Patients were stratified as high expression (a score of 3) or low expression (scores 0-2).
In all, 29%) of patients had high IGF-IR expression – which was significantly correlated with negative lymph nodes. In patients older than 55 years, there was no survival difference between those with low and high IGF-IR expression.
IGF-IR belongs to the large class of tyrosine kinase receptors that appear to control proliferation and apoptosis in tumors, and may play a role in resistance to chemotherapy.
The study was presented in Denver as a poster at the AACR's International Conference on Molecular Diagnostics in Cancer Therapeutic Development.
One of the coauthors is employed by Ventana Medical Systems, which makes an anti-IGF1-R antibody and is developing an IGF-IR probe.