Identification of microRNA-214 as a negative regulator of colorectal cancer liver metastasis by way of regulation of fibroblast growth factor receptor 1 expression.

UNLABELLED: The purpose of this study was to identify microRNAs (miRNAs) involved in the pathology of colorectal cancer (CRC) liver metastasis and investigate their underlying mechanisms. A total of 39 miRNAs were identified to be differentially expressed between 16 primary CRC tissues with liver metastases and 16 CRC tissues without liver metastases from 32 patients by Affymetric miRNA microarrays. A panel of eight miRNAs were confirmed to be significantly and differentially expressed between CRC tissues with and without liver metastases through quantitative reverse-transcription polymerase chain reaction (RT-PCR) analysis in the 32 patients. In a validated cohort of 99 CRC patients (44 with and 55 without liver metastases), only miR-214 was validated to be significantly down-regulated in CRC with liver metastases, which was associated with an unfavorable prognosis. Ectopic expression of miR-214 suppressed proliferation, migration, and invasion in vitro, tumor growth and liver metastasis in an in vivo xenograft mouse model, whereas miR-214 knockdown promoted proliferation, migration, and invasion in CRC cell lines. Further studies indicated that fibroblast growth factor receptor 1 (FGFR1) was a potential target of miR-214. Restoring miR-214 expression in CRC cells decreased endogenous FGFR1 messenger RNA (mRNA) and protein levels. FGFR1 knockdown mimicked the tumor suppressive effect of miR-214 on CRC cells, while reintroduction of FGFR1 abolished the tumor suppressive effect of miR-214 on CRC cells. Moreover, miR-214 expression levels were inversely correlated with FGFR1 in CRC patients. CONCLUSION: Down-regulation of miR-214 expression was correlated with increased FGFR1 expression levels, which may contribute to increased CRC liver metastasis. miR-214 may serve as a potential marker to predict survival, and the miR-214-FGFR1 axis may be a therapeutic target in CRC patients.

Dietary energy balance modulates epithelial-to-mesenchymal transition and tumor progression in murine claudin-low and basal-like mammary tumor models.

Using novel murine models of claudin-low and basal-like breast cancer, we tested the hypothesis that diet-induced obesity (DIO) and calorie restriction (CR) differentially modulate progression of these aggressive breast cancer subtypes. For model development, we characterized two cell lines, "mesenchymal (M)-Wnt" and "epithelial (E)-Wnt," derived from MMTV-Wnt-1 transgenic mouse mammary tumors. M-Wnt, relative to E-Wnt, cells were tumor-initiating cell (TIC)-enriched (62% vs. 2.4% CD44(high)/CD24(low)) and displayed enhanced ALDEFLUOR positivity, epithelial-to-mesenchymal transition (EMT) marker expression, mammosphere-forming ability, migration, invasion, and tumorigenicity (P < 0.001; each parameter). M-Wnt and E-Wnt cells clustered with claudin-low and basal-like breast tumors, respectively, in gene expression profiles and recapitulated these tumors when orthotopically transplanted into ovariectomized C57BL/6 mice. To assess the effects of energy balance interventions on tumor progression and EMT, mice were administered DIO, control, or CR diets for 8 weeks before orthotopic transplantation of M-Wnt or E-Wnt cells (for each cell line, n = 20 mice per diet) and continued on their diets for 6 weeks while tumor growth was monitored. Relative to control, DIO enhanced M-Wnt (P = 0.01), but not E-Wnt, tumor progression; upregulated EMT- and TIC-associated markers including N-cadherin,fibronectin, TGFß, Snail, FOXC2, and Oct4 (P < 0.05, each); and increased intratumoral adipocytes. Conversely, CR suppressed M-Wnt and E-Wnt tumor progression (P < 0.02, each) and inhibited EMT and intratumoral adipocyte accumulation. Thus, dietary energy balance interventions differentially modulate EMT and progression of claudin-low and basal-like tumors. EMT pathway components may represent targets for breaking the obesity-breast cancer link, particularly for preventing and/or controlling TIC-enriched subtypes such as claudin-low breast cancer.

TrkBT1 induces liver metastasis of pancreatic cancer cells by sequestering Rho GDP dissociation inhibitor and promoting RhoA activation.

Many genetic and molecular alterations, such as K-ras mutation and NF-kappaB activation, have been identified in pancreatic cancer. However, the mechanisms by which pancreatic cancer metastasizes still remain to be determined. Although we previously showed that the tropomyosin-related kinase B (TrkB) was significantly correlated with the development of liver metastasis, its function in pancreatic cancer metastasis remained unresolved. In the present study, we showed that overexpressed TrkB is an alternatively spliced transcript variant of TrkB (TrkBT1) with a unique COOH-terminal 12-amino acid sequence and is mainly localized in the cytoplasm. Our results showed that overexpression of Flag-tagged TrkBT1 but not a Flag-tagged TrkBT1 COOH-terminal deletion mutant (Flag-TrkBT1DeltaC) in nonmetastatic pancreatic cancer cells enhanced cell proliferation, promoted formation of colonies in soft agar, stimulated tumor cell invasion, and induced liver metastasis in an orthotopic xenograft mouse model of pancreatic cancer. TrkBT1 interacted with Rho GDP dissociation inhibitor (GDI) in vivo, but Flag-TrkBT1DeltaC did not. Furthermore, overexpression of Flag-TrkBT1 and knockdown of RhoGDI expression by RhoGDI short hairpin RNAs promoted RhoA activation, but Flag-TrkBT1DeltaC overexpression did not. Therefore, our results showed that TrkBT1 overexpression induces liver metastasis of pancreatic cancer and uncovered a unique signaling mechanism by which TrkBT1 sequesters GDI and activates RhoA signaling.