Recent advances in the field of circulating tumor cells (CTC) have shown promise in this liquid biopsy-based prognosis of patient outcome. However, not all of the circulating cells are tumor cells, as evidenced by a lack of tumor-specific markers. The current FDA standard for capturing CTCs (CellSearch) relies on an epithelial marker and cells captured via CellSearch cannot be considered to have undergone EMT. Therefore, it is difficult to ascertain the presence and relevance of any mesenchymal or EMT-like CTCs. To address this gap in technology, we recently discovered the utility of cell-surface vimentin (CSV) as a marker for detecting mesenchymal CTCs from sarcoma, breast, and colon cancer. Here we studied peripheral blood samples of 48 prostate cancer (PCA) patients including hormone sensitive and castration resistant sub-groups. Blood samples were analyzed for three different properties including our own CSV-based CTC enumeration (using 84-1 mAb against CSV), CellSearch-based epithelial CTC counts, and serum prostate-specific antigen (PSA) quantification. Our data demonstrated that in comparison with CellSearch, the CSV-based method had greater sensitivity and specificity. Further, we observed significantly greater numbers of CTCs in castration resistant patients as measured by our CSV method but not CellSearch. Our data suggests CSV-guided CTC enumeration may hold prognostic value and should be further validated as a possible measurement of PCA progression towards the deadly, androgen-independent form.

BackgroundInsulin-like growth factor I (IGF-I) can induce epithelial mesenchymal transition (EMT) in many epithelial tumors; however, the molecular mechanism by which this occurs is not clearly understood. Additionally, little is known about the involvement of IGF-I in gastric cancer.MethodsTwo gastric cancer cell lines were treated with IGF-I to induce EMT and levels of transcription factor ZEB2 and microRNA-200c (miR-200c) were measured. Cells were treated with Akt/ERK inhibitors to investigate the role of these pathways in IGF-I-mediated EMT. Transfection of shRNA plasmids was used to silence the ubiquitin ligase Cbl-b to assess its involvement in this process. The relationship between IGF-IR and Cbl-b expression, and the effect of IGF-IR and Cbl-b on metastasis were analyzed in primary gastric adenocarcinoma patients.ResultsIGF-I-induced gastric cancer cell EMT was accompanied by ZEB2 up-regulation. Furthermore, both Akt/ERK inhibitors and knockdown of Akt/ERK gene reversed IGF-I-induced ZEB2 up-regulation and EMT through up-regulation of miR-200c, suggesting the involvement of an Akt/ERK-miR-200c-ZEB2 axis in IGF-I-induced EMT. The ubiquitin ligase Cbl-b also ubiquitinated and degraded IGF-IR and inhibited the Akt/ERK-miR-200c-ZEB2 axis, leading to the repression of IGF-I-induced EMT. There was a significant negative correlation between the expression of IGF-IR and Cbl-b in gastric cancer patient tissues (r = -0.265, p < 0.05). More of patients with IGF-IR-positive expression and Cbl-b-negative expression were with lymph node metastasis (p < 0.001).ConclusionsTogether, these findings demonstrate that the ubiquitin ligase Cbl-b represses IGF-I-induced EMT, likely through targeting IGF-IR for degradation and further inhibiting the Akt/ERK-miR-200c-ZEB2 axis in gastric cancer cells.

The insulin-like growth factor-I (IGF-I) signaling induces epithelial to mesenchymal transition (EMT) program and contributes to metastasis and drug resistance in several subtypes of tumors. In preclinical studies, targeting of the insulin-like growth factor-I receptor (IGF-IR) showed promising anti-tumor effects. Unfortunately, high expectations for anti-IGF-IR therapy encountered challenge and disappointment in numerous clinical trials. This review summarizes the regulation of EMT by IGF-I/IGF-IR signaling pathway and drug resistance mechanisms of targeting IGF-IR therapy. Most importantly, we address several factors in the regulation of IGF-I/IGF-IR-associated EMT progression that may be potential predictive biomarkers in targeted therapy.