RET and thyroid gland papillary carcinoma: Furthermore, in another study by Borrello et al. (2005), it was reported that transforming oncogene RET/PTC1 in human papillary thyroid carcinoma can induce the expression of CXCL12 and its receptor CXCR4, thus triggering autocrine proliferation of thyroid carcinoma cells (Borrello et al., 2005).