The biomarker GP88 (progranulin) is expressed in forms of breast cancer called invasive ductal carcinoma (IDC) and ductal carcinoma in situ (DCIS) but is not seen in normal breast tissue or in other types of breast cancer. This means that the protein could have potential as a biomarker in diagnosis and in monitoring disease.
In studies looking at samples of estrogen receptor-positive patients with IDC, researchers linked levels of GP88 with patients' survival outcomes, and the results showed that increases in GP88 were connected with shorter survival time and significantly increased risk of disease recurrence. GP88 was still valuable in predicting outcomes after 5 years or more.
According to the researchers from A&G Pharmaceutical and a number of U.S. universities, it would be interesting to see whether levels of GP88 expression could be used to decide on treatment for patients with IDC, as it has been linked with drug resistance in other studies. GP88 is found in circulating blood as well as in breast cancer tissue. It could therefore be worthwhile to compare the levels of GP88 in the blood and breast cancer tissue samples, to assess the validity of the biomarker in blood tests. Further studies are needed to investigate these possibilities.
In September 2010, A&G Pharmaceutical got a $1.2 million SBIR grant to develop a therapeutic antibody targeted against GP88 for the treatment of breast cancer. The company currently is developing GP88-based diagnostics.