BRCA1 and cancer: Furthermore, epidemiologic studies have shown that high levels of plasmatic IGF are correlated with an increased risk of several cancers, including breast, and that IGF-2 signaling is possibly associated with cancer progression [8]; it is also known that the loss of tumor suppressor genes such as BRCA1, p53, and PTEN leads to an increase in IGF-1R expression in tumors [9].