The rearranged during transfection/papillary thyroid carcinoma tyrosine kinase is an estrogen-dependent gene required for the growth of estrogen receptor positive breast cancer cells

Abstract

The rearranged during transfection/papillary thyroid carcinoma (RET/PTC) tyrosine kinase is an oncogene implicated in the tumorigenesis of thyroid cancer. Recent studies by us and others have shown that RET/PTC kinase expression is induced by estrogen in breast cancer cells. Due to the critical involvement of estrogen-regulated genes in the pathogenesis of breast cancer, we investigated the expression, regulation and function of RET/PTC kinase in breast cancer cells. We found that RET/PTC kinase expression correlates with ER expression in breast cancer cells and tumor specimens, and that RET/PTC kinase expression is associated with a poor prognosis in ER-positive breast cancer patients. We found that estrogen rapidly induces RET/PTC kinase expression in an estrogen receptor (ER)-dependent manner in breast cancer cells and that this induction is through a transcriptional regulatory mechanism. Using reporter assays, small interfering RNA (siRNA) assays, and chromatin immunoprecipitation (ChIP) assays, we demonstrated the necessity of crosstalk between ER and the forkhead box A1 (FOXA1) transcription factor in regulating RET/PTC kinase expression. In functional studies, increased expression of RET/PTC kinase induced by estrogen stimulation resulted in elevated phosphorylation of multiple downstream kinase signaling pathways. Conversely, knockdown of RET/PTC expression was associated with the inhibition of these same kinase signaling pathways, and, in fact, decreased the stimulatory effect of estrogen on the proliferation of ER-positive breast cancer cells. These results demonstrate a novel pathway of ER and FOXA1 transcription factor crosstalk in regulating RET/PTC kinase expression, and demonstrate that RET/PTC kinase is a critical regulator for the proliferation of ER-positive breast cancer cells. Taken together, our study suggests that RET/PTC kinase may serve as a novel prognostic biomarker and therapeutic target for prevention and treatment of ER-positive breast cancer.

210 Genetic and epigenetic factors affect RET gene expression in breast cancer cell lines and influence survival in patients

“…A similar experiment has already been carried out in the ER-cell line MDA231, physiologically expressing very low levels of RET [36]. After Nabut treatments, and compared to untreated cells, we observed a dosedependent increase of RET expression ( Figure 5C, left panel) while the ESR1 mRNA levels resulted significantly enhanced after Nabut 5nM, but undetectable for lower concentrations ( Figure 5C, right panel).…”

“…Regulatory elements responsive to this latter receptor are located at -50kb and + 32kb from the RET gene [35,36]. Moreover, additional target elements are located in the RET locus [37,38].…”

Two-Tiered Control of Epithelial Growth and Autophagy by the Insulin Receptor and the Ret-Like Receptor, Stitcher

“…Although the signals that activate the Drosophila Ret-like proteins remain unknown, Stit is activated upon epidermal wounding to initiate re-epithelialization and barrier repair. Mammalian Ret is activated by GDNF to instruct epithelial morphogenesis in the uteric duct of the kidney [31] and Ret-activating mutations have been implicated in a variety of human cancers including epithelial cancers (breast and lung) and multiple endocrine neoplasia ( men2 ) [32]–[35]. More recently, overexpression of an activated form of Drosophila Ret that mimics the mutation that leads to men2 has been used to identify potential Ret signal transducers and drugs that interfere with its aberrant activation [36].…”

Preclinical Efficacy and Safety Assessment of an Antibody–Drug Conjugate Targeting the c-RET Proto-Oncogene for Breast Carcinoma

“…Increased RET expression has been associated with decreased metastasis-free survival (HR, 2.12; P ¼ 0.0476) and overall survival (HR, 1.95; P ¼ 0.0438) in patients with breast cancer (15), and RET inhibition decreased growth and metastasis of ER þ breast cancer cells (15,16). Increased expression of RET has also been observed in primary tumors from patients who have failed tamoxifen therapy, suggesting a role for RET in endocrine resistance (17).…”