Insulin receptor alternative splicing in breast and prostate cancer.

Cancer etiology represents an intricate, multifactorial orchestration where metabolically associated insulin-like growth factors (IGFs) and insulin foster cellular proliferation and growth throughout tumorigenesis. The insulin receptor (IR) exhibits two splice variants arising from alternative mRNA processing, namely IR-A, and IR-B, with remarkable distribution and biological effects disparities. This insightful review elucidates the structural intricacies, widespread distribution, and functional significance of IR-A and IR-B. Additionally, it explores the regulatory mechanisms governing alternative splicing processes, intricate signal transduction pathways, and the intricate association linking IR-A and IR-B splicing variants to breast and prostate cancer tumorigenesis. Breast cancer and prostate cancer are the most common malignant tumors with the highest incidence rates among women and men, respectively. These findings provide a promising theoretical framework for advancing preventive strategies, diagnostic modalities, and therapeutic interventions targeting breast and prostate cancer.

RNA-binding protein CUGBP1 controls the differential INSR splicing in molecular subtypes of breast cancer cells and affects cell aggressiveness.

The insulin receptor gene (INSR) undergoes alternative splicing to give rise to two functionally related, but also distinct, isoforms IR-A and IR-B, which dictate proliferative and metabolic regulations, respectively. Previous studies identified the RNA-binding protein CUGBP1 as a key regulator of INSR splicing. In this study, we show that the differential splicing of INSR occurs more frequently in breast cancer than in non-tumor breast tissues. In breast cancer cell lines, the IR-A:IR-B ratio varies in different molecular subtypes, knockdown or overexpression of CUGBP1 gene in breast cancer cells altered IR-A:IR-B ratio through modulation of IR-A expression, thereby reversed or enhanced the insulin-induced oncogenic behavior of breast cancer cells, respectively. Our data revealed the predominant mitogenic role of IR-A isoform in breast cancer and depicted a novel interplay between INSR and CUGBP1, implicating CUGBP1 and IR-A isoform as the potential therapeutic targets and biomarkers for breast cancer.

TIAM1 Upregulation Confers NVP-BEZ235 Resistance to Breast Cancer Cells Through FGFR/STAT3 Pathway.

Breast cancer is the most common cancer in women worldwide, and advanced breast cancer is the leading cause of cancer death in women. In present study, we aim to investigate that role of T-cell lymphoma invasion and metastasis-inducing protein1 (TIAM1) on NVP-BEZ235 resistance to breast cancer MCF7 and MDA-MB-361 cells. Briefly, MCF7 and MDA-MB-361 cells were treated with NVP-BEZ235 and the relative expressions of TIAM1 at both mRNA level and protein level were determined by RT-PCR and western blot. In addition, MCF7 and MDA-MB-361 cells were transfected with TIAM1 knockdown or overexpression vector. Then the IC50 of NVP-BEZ235 on MCF7 and MDA-MB-361 cells were detected by MTT assay. Finally, FGFR/STAT3 pathway protein members were investigated by western blot. Consequently, we found that the mRNA and protein expressions of TIAM1 and FGFR1/3 were dramatically upregulated in NVP-BEZ235-treated group in both MCF7 and MDA-MB-361 cells. Interestingly, TIAM1 knockdown via shRNA decreased the IC50 of NVP-BEZ235 of breast cancer cells, while TIAM1 overexpression increased the IC50 of NVP-BEZ235 of breast cancer cells, which suggested that TIAM1 was one of the contributors for NVP-BEZ235 resistance. In addition, FGFR members including FGFR1/3 showed similar results to TIAM1. Importantly, FGFR inhibitor AZD4547 decreased the IC50 of NVP-BEZ235, which suggested that FGFR downregulation reduced the NVP-BEZ235 resistance to breast cancer cells. In summary, our present study revealed that TIAM1 conferred NVP-BEZ235 resistance to breast cancer cells via activating FGFR/STAT3 pathway.

Identification of differentially expressed genes-related prognostic risk model for survival prediction in breast carcinoma patients.

Since the imbalance of gene expression has been demonstrated to tightly related to breast cancer (BRCA) genesis and growth, common genes expressed of BRCA were screened to explore the essence in-between. In current work, most common differentially expressed genes (DEGs) in various subtypes of BRCA were identified. Functional enrichment analysis illustrated the driving factor of deactivation of the cell cycle and the oocyte meiosis, which critically triggers the development of BRCA. Herein, we constructed a 12-gene prognostic risk model relative to differential gene expression. Subsequently, the K-M curves, analysis on time-ROC curve and Cox regression were performed to assess this risk model by determining the respective prognostic value, and the prediction performance were ascertained for both training and validation cohorts. In addition, multivariate Cox regression was analysed to reveal the independence between risk score and prognostic stage, and the accuracy and sensitivity of prognosis are particularly improved after clinical indicators are included into the analysis. In summary, this study offers novel insights into the imbalance of gene expression within BRCA, and highlights 12 selected genes associated with patient prognosis. The risk model can help individualize treatment for patients at different risks, and propose precise strategies and treatments for BRCA therapy.

PRAS40 hyperexpression promotes hepatocarcinogenesis.

BACKGROUND: Hepatocellular carcinoma (HCC) is one of the most common cancers, whereas the molecular mechanism remains largely unknown. PRAS40 (encoded by AKT1S1) phosphorylation was increased in human melanoma, prostate cancer and lung cancer specimens, which was considered as the results of Akt activation. However the mechanism in detail and its role in HCC stay elusive. METHODS: PRAS40 expression and phosphorylation were analyzed in HCC specimens, and the survival rates of patients were investigated. Functional analyses of PRAS40 in HCC were performed in vivo and in vitro. The miR-124-3p binding sites in PRAS40 were investigated using luciferase assay. MiR-124-3p expression in HCC specimens was examined by In Situ hybridization, and the correlation to PRAS40 level was evaluated. FINDINGS: The phosphorylation, protein and mRNA levels of PRAS40 were increased significantly in HCC specimens from our cohorts and TCGA database, which was positively correlated to the poor prognosis of HCC patients. Compared to Akt1s1+/+ mice, hepatocarcinogenesis was suppressed in Akt1s1-/- mice, and the activation of Akt was impaired. PRAS40 depletion resulted in the inhibition of HCC cellular proliferation. Tumor suppressor miR-124-3p was found to downregulate PRAS40 expression by targeting its 3'UTR. MiR-124-3p levels were inversely correlated to PRAS40 protein and phosphorylation levels in HCC specimens. The proliferation inhibition by miR-124-3p mimics was partially reversed by exogenous PRAS40 introduction in HCC cells. INTERPRETATION: PRAS40 hyperexpression induced by loss of miR-124-3p contributes to PRAS40 hyperphosphorylation and hepatocarcinogenesis. These results could be expected to offer novel clues for understanding hepatocarcinogenesis and developing approaches.

Targeting the EphB4 receptor tyrosine kinase sensitizes HER2-positive breast cancer cells to Lapatinib.

Clinical data analysis reveals that the expression of the EphB4 receptor tyrosine kinase is significantly elevated in HER2-positive breast cancer and high levels of EphB4 strongly correlate with poor disease prognosis. However, the impact of EphB4 activation on HER2-positive breast cancer cells and the potential of EphB4 as a therapeutic target remain to be explored. Here, we show that EphB4 overexpression confers gain-of-function activities to HER2-positive breast cancer cells, rendering resistance to a HER2/EGFR inhibitor Lapatinib. Furthermore, using integrated transcriptomic and tyrosine phosphoproteomic analyses, followed by biochemical confirmation, we establish that EphB4 activation engages the SHP2/GAB1-MEK signaling cascade and downstream c-MYC activation, and thereby limits the overall drug responses to Lapatinib. Finally, we demonstrate that, in HER2-positive breast tumors, inhibition of EphB4 combined with Lapatinib is more effective than either alone. These findings provide new insights into the signaling networks dictating therapeutic response to Lapatinib as well as a rationale for co-targeting EphB4 in HER2-positive breast cancer.

The coexpression of EphB4 and EphrinB2 is associated with poor prognosis in HER2-positive breast cancer.

OBJECTIVE: HER2 overexpression is associated with aggressive phenotypes in breast cancer, including increased tumor proliferation, greater invasiveness, and reduced overall survival. The overall response rate to HER2-targeted therapies remains <30%. There is an urgent need for the identification of efficient markers to predict patients with a poor prognosis. This study was designed to investigate the correlation between EphB4 and EphrinB2 expression and the clinicopathological characteristics of HER2-positive breast cancer. MATERIALS AND METHODS: A total of 111 primary HER2-positive breast cancer patients were enrolled in this study (diagnosed since December 2005 to November 2010 from the Second Hospital of Dalian Medical University). The protein expression of EphB4 and EphrinB2 was examined by immunohistochemistry using paraffin-embedded tumor tissues. RESULTS: There was a significant correlation between EphB4 and EphrinB2 expression (P=0.013, r=0.255). Kaplan-Meier analysis showed that the prognosis of patients with a high expression of both EphB4 and EphrinB2 was significantly worse than the prognosis of patients with either EphB4 or EphrinB2 expression and patients with negative expression (hazard ratio [HR] =1.935, P=0.0224). However, high expression of EphB4 or EphrinB2 alone was not an independent prognostic factor to predict worse overall survival. To summarize, HER2-positive breast cancer patients with overexpression of both EphB4 and EphrinB2 were associated with the worst prognosis. CONCLUSION: High expression of EphB4 and EphrinB2 correlated with poor overall survival, which can serve as an independent prognostic indicator in primary HER2-positive breast cancer patients.

Exceptionally high UBE2C expression is a unique phenomenon in basal-like type breast cancer and is regulated by BRCA1.

Ubiquitin-conjugating enzyme 2C (UBE2C) is overexpressed in various types of cancer, leading to poor outcomes and drug resistance. UBE2C may also have a critical role in phenotypes associated with poor prognosis in breast cancer; however, the relationship between UBE2C expression and clinical outcome in breast cancer subtypes has not previously been investigated. We firstly analyzed breast cancer patient data and immunohistochemistry of breast cancer patient samples. We demonstrated that UBE2C was associated with poor prognosis in breast cancer, particularly basal-like breast cancer, a subtype with aggressive clinical features. Interestingly, we found that there was a close relationship between the expression of BRCA1 and UBE2C in the MCF-7 and MDA-MB-231 breast cancer cell lines. Upregulation of BRCA1 could inhibit the expression of UBE2C. In cells with BRCA1 silenced down, expression of UBE2C was obviously increased, with a concurrent decrease in cellular sensitivity to doxorubicin. Suppression of UBE2C expression by RNA interference led to decrease the mRNA expressions of BCRP, MRP1 and P-gp in doxorubicin-treated MDA-MB-231 cells. Moreover, treatment with 1µg/ml doxorubicin led to increased expression of UBE2C. The results show high expression of UBE2C is a potential prognostic factor of poor outcome in basal-like breast cancer. Moreover, loss of BRCA1 function results in an increase in UBE2C expression and chemical resistance to doxorubicin in breast cancer cells.

The role of EphB4 and IGF-IR expression in breast cancer cells.

OBJECTIVE: to investigate the role of EphB4 and IGF-1R in the proliferation and migration of breast cancer. METHODS: The relative mRNA levels of EphB4 were measured by RT-PCR. The proliferation of the cells was determined by MTT assay, and cells migration and invasive ability was analyzed using the scratch migration assay. RESULTS: The expression of EphB4 in control group was significantly decreased when compared with IGF-I group (P<0.001). The expression of EphB4 in IGF-I+LY and LY group were lower than that of the control group (P<0.001).The cell proliferation and migration ability of the cells in IGF-I group increased significantly compared to the cells in the control group (P<0.001), while the cells in IGF-1+LY group and LY group showed a decreased proliferation and migration ability compared to the control group (P<0.001). CONCLUSION: IGF-IR might be a upstream gene of EphB4. Besides, higher expression of EphB4 shows increased tumor proliferation and migration in breast cells. The study of EphB4 upstream gene and signaling pathway can provide more targeted anti-tumor point selection for targeted therapy.