IRS2 and small cell lung carcinoma: The connection of IRS-2 with tumor progression is substantiated by the observation that IRS-2 protein expression is elevated in later disease stages in many cancers including breast, prostate and peripheral nerve sheath tumors [31–33] and the IRS2 gene is amplified in additional malignancies including colorectal cancer (CRC) and small cell lung cancer [34, 35].