SOCS1 function in BCR-ABL mediated myeloproliferative disease is dependent on the cytokine environment.

Treatment with tyrosine kinase inhibitors is the standard of care for Philadelphia chromosome positive leukemias. However the eradication of leukemia initiating cells remains a challenge. Circumstantial evidence suggests that the cytokine microenvironment may play a role in BCR-ABL mediated leukemogenesis and in imatinib resistance. Gene expression analyses of BCR-ABL positive ALL long-term cultured cells revealed strong reduction of SOCS mRNA expression after imatinib treatment, thereby demonstrating a strong inhibition of cytokine signaling. In this study we employed SOCS1-a strong inhibitor of cytokine signaling-as a tool to terminate external cytokine signals in BCR-ABL transformed cells in vitro and in vivo. In colony formation assays with primary bone marrow cells, expression of SOCS1 decreased colony numbers under pro-proliferative cytokines, while it conferred growth resistance to anti-proliferative cytokines. Importantly, co-expression of SOCS1 with BCR-ABL led to the development of a MPD phenotype with a prolonged disease latency compared to BCR-ABL alone in a murine bone marrow transplantation model. Interestingly, SOCS1 co-expression protected 20% of mice from MPD development. In summary, we conclude that under pro-proliferative cytokine stimulation at the onset of myeloproliferative diseases SOCS1 acts as a tumor suppressor, while under anti-proliferative conditions it exerts oncogenic function. Therefore SOCS1 can promote opposing functions depending on the cytokine environment.

The Phosphatases STS1 and STS2 Regulate Hematopoietic Stem and Progenitor Cell Fitness.

FLT3 and c-KIT are crucial regulators of hematopoietic stem and progenitor cells. We investigated the role of STS1 and STS2 on FLT3 and c-KIT phosphorylation, activity, and function in normal and stress-induced hematopoiesis. STS1/STS2-deficient mice show a profound expansion of multipotent progenitor and lymphoid primed multipotent progenitor cells with elevated colony-forming capacity. Although long-term hematopoietic stem cells are not increased in numbers, lack of STS1 and STS2 significantly promotes long-term repopulation activity, demonstrating a pivotal role of STS1/STS2 in regulating hematopoietic stem and progenitor cell fitness. Biochemical analysis identified STS1/STS2 as direct phosphatases of FLT3 and c-KIT. Loss of STS1/STS2 induces hyperphosphorylation of FLT3, enhances AKT signaling, and confers a strong proliferative advantage. Therefore, our study reveals that STS1 and STS2 may serve as novel pharmaceutical targets to improve hematopoietic recovery after bone marrow transplantation.

Development of a molecular multimarker assay for the analysis of circulating tumor cells in adenocarcinoma patients.

BACKGROUND: The analysis of circulating tumor cells (CTCs) is emerging as a promising diagnostic tool in oncology. However, even if a variety of methods for CTC isolation have been already developed, their specificity and/or sensitivity still remain problematic. The aim of this study was to develop an immunomagnetic/real-time reverse transcription polymerase chain reaction (RT-PCR) assay for the molecular detection of circulating tumor cells (CTCs) in peripheral blood (PB) of adenocarcinoma cancer patients. METHODS: The presence of CTCs was evaluated in 945 PB blood samples from 247 adenocarcinoma cancer patients and in 42 healthy controls by immunomagnetic enrichment using the antibodies BM7 and VU1D9 followed by real-time RT-PCR analysis of the marker genes KRT19, MUC1, EPCAM, CEACAM5, BIRCS, SCGB2A2, and ERBB2. RESULTS: The developed assay showed not only high specificity, as none of the healthy controls were found positive for the multimarker gene panel, but also great sensitivity as CTCs were detected in adenocarcinomas arising from 10 different organs. According to tumor primary origin, CTC positivity was detected in 33.3% of Ampulla of Vater adenocarcinomas, 69.6% of bile ducts adenocarcinomas, 61.3% of breast adenocarcinomas, 61.3% of cardia adenocarcinomas, 60.6% of colon adenocarcinomas, 66.7% of esophagus adenocarcinomas, 57.1% of pancreas adenocarcinomas, 66.7% of rectum adenocarcinomas, 33.3% of small intestine adenocarcinomas, and 62.2% of stomach adenocarcinomas. CONCLUSIONS: Our results suggest that the current developed technique can be used to detect CTCs in all major adenocarcinomas, with great sensitivity without compromising specificity.

Multimarker gene analysis of circulating tumor cells in pancreatic cancer patients: a feasibility study.

OBJECTIVE: The aim of this study was to develop an immunomagnetic/real-time reverse transcriptase polymerase chain reaction (RT-PCR) assay and assess its clinical value for the molecular detection of circulating tumor cells (CTCs) in peripheral blood of pancreatic cancer patients. METHODS: The presence of CTCs was evaluated in 34 pancreatic cancer patients before systemic therapy and in 40 healthy controls, through immunomagnetic enrichment, using the antibodies BM7 and VU1D9 [targeting mucin 1 and epithelial cell adhesion molecule (EpCAM), respectively], followed by real-time RT-PCR analysis of the genes KRT19, MUC1, EPCAM, CEACAM5 and BIRC5. RESULTS: The developed assay showed high specificity, as none of the healthy controls were found to be positive for the multimarker gene panel. CTCs were detected in 47.1% of the pancreatic cancer patients before the beginning of systemic treatment. Shorter median progression-free survival (PFS) was observed for patients who had at least one detectable tumor-associated transcript, compared with patients who were CTC negative. Median PFS time was 66.0 days [95% confidence interval (CI) 44.8-87.2] for patients with baseline CTC positivity and 138.0 days (95% CI 124.1-151.9) for CTC-negative patients (p = 0.01, log-rank test). CONCLUSION: Our results suggest that in addition to the current prognostic methods, CTC analysis represents a potential complementary tool for prediction of outcome in pancreatic cancer patients.