The role of transient receptor potential vanilloid 2 channel in cardiac aging

BACKGROUND

The aging heart is characterized by cellular and molecular changes leading to a decline in physiologic function and cardiac remodeling, specifically the development of myocyte hypertrophy and fibrosis. Transient receptor potential vanilloid 2 (TRPV2), a stretch-mediated channel and regulator of calcium homeostasis, plays a key role in the function and structure of the heart. TRPV2 also plays an important role in the adaptive and maladaptive compensatory mechanisms of the heart in response to pathologic and exercise-induced stress. Our current study seeks to elucidate the potential role of TRPV2 channels in the regulation of cardiac function in aging.

METHODS

Wild-type (WT) and TRPV2 functional knockout (FKO) mice were aged out to various time points, and their cardiac function was measured using advanced echocardiography. Furthermore, we histologically analyzed the heart morphology to determine myocyte hypertrophy, the development of fibrosis and the relative expression of TRPV2.

RESULTS

Our results demonstrate that even though TRPV2-FKO mice have impaired function at baseline, their cardiac function as measured via standard and advanced echocardiographic parameters (ejection fraction, cardiac output and circumferential strain) decreased less with aging in comparison with the WT group. Furthermore, there was less fibrosis and hypertrophy in the TRPV2-FKO group with aging in comparison with the WT. The expression of TRPV2 in the WT group did not significantly change with aging.

CONCLUSIONS

TRPV2 functional deletion is compatible with aging and associated with a decreased development of myocyte hypertrophy and fibrosis. It may be an important target for prevention of age-induced cardiac remodeling.

Transient Receptor Potential Vanilloid 2 Regulates Myocardial Response to Exercise

The myocardial response to exercise is an adaptive mechanism that permits the heart to maintain cardiac output via improved cardiac function and development of hypertrophy. There are many overlapping mechanisms via which this occurs with calcium handling being a crucial component of this process. Our laboratory has previously found that the stretch sensitive TRPV2 channels are active regulators of calcium handling and cardiac function under baseline conditions based on our observations that TRPV2-KO mice have impaired cardiac function at baseline. The focus of this study was to determine the cardiac function of TRPV2-KO mice under exercise conditions. We measured skeletal muscle at baseline in WT and TRPV2-KO mice and subjected them to various exercise protocols and measured the cardiac response using echocardiography and molecular markers. Our results demonstrate that the TRPV2-KO mouse did not tolerate forced exercise although they became increasingly exercise tolerant with voluntary exercise. This occurs as the cardiac function deteriorates further with exercise. Thus, our conclusion is that TRPV2-KO mice have impaired cardiac functional response to exercise.

Foxm1 expression in prostate epithelial cells is essential for prostate carcinogenesis

The treatment of advanced prostate cancer (PCa) remains a challenge. Identification of new molecular mechanisms that regulate PCa initiation and progression would provide targets for the development of new cancer treatments. The Foxm1 transcription factor is highly up-regulated in tumor cells, inflammatory cells, and cells of tumor microenvironment. However, its functions in different cell populations of PCa lesions are unknown. To determine the role of Foxm1 in tumor cells during PCa development, we generated two novel transgenic mouse models, one exhibiting Foxm1 gain-of-function and one exhibiting Foxm1 loss-of-function under control of the prostate epithelial-specific Probasin promoter. In the transgenic adenocarcinoma mouse prostate (TRAMP) model of PCa that uses SV40 large T antigen to induce PCa, loss of Foxm1 decreased tumor growth and metastasis. Decreased prostate tumorigenesis was associated with a decrease in tumor cell proliferation and the down-regulation of genes critical for cell proliferation and tumor metastasis, including Cdc25b, Cyclin B1, Plk-1, Lox, and Versican. In addition, tumor-associated angiogenesis was decreased, coinciding with reduced Vegf-A expression. The mRNA and protein levels of 11β-Hsd2, an enzyme playing an important role in tumor cell proliferation, were down-regulated in Foxm1-deficient PCa tumors in vivo and in Foxm1-depleted TRAMP C2 cells in vitro. Foxm1 bound to, and increased transcriptional activity of, the mouse 11β-Hsd2 promoter through the -892/-879 region, indicating that 11β-Hsd2 was a direct transcriptional target of Foxm1. Without TRAMP, overexpression of Foxm1 either alone or in combination with inhibition of a p19(ARF) tumor suppressor caused a robust epithelial hyperplasia, but was insufficient to induce progression from hyperplasia to PCa. Foxm1 expression in prostate epithelial cells is critical for prostate carcinogenesis, suggesting that inhibition of Foxm1 is a promising therapeutic approach for prostate cancer chemotherapy.

Comparison of three mathematical models for predicting the risk of additional axillary nodal metastases after positive sentinel lymph node biopsy in early breast cancer

Background

Women with breast cancer and a positive axillary sentinel lymph node (SLN) are recommended to undergo complete axillary lymph node dissection; however, further nodal disease is not always present. Mathematical models have been constructed to determine the risk of metastatic disease; three of these were evaluated independently.

Methods

Data from 108 women with breast cancer who had a positive SLN biopsy and completion axillary lymph node dissection were used. Measurements of additional parameters over those usually determined (such as size of SLN metastasis) were assessed under the supervision of two pathologists. These data were used to determine the predicted risk of non-SLN metastases using three mathematical models (from Memorial Sloan-Kettering Cancer Center (MSKCC), Cambridge University and Stanford University) and a comparison made with the observed findings. Analyses were made using the area under the receiver operating characteristic (ROC) curve (AUC).

Results

Some 53 (49·1 per cent) of 108 patients had a positive non-sentinel axillary lymph node metastasis. The AUC values were 0·63, 0·72 and 0·67 for the MSKCC, Cambridge and Stanford nomograms respectively.

Conclusion

This independent comparison found no significant difference between the models, although the Cambridge model had the advantage of requiring fewer measurements with a more accurate predictive performance.

CGH analysis of ductal carcinoma of the breast with basaloid/myoepithelial cell differentiation

2-18% of ductal carcinoma-No Special Type (NST) are reported to express basal cell keratin 14 and such tumours may have a different metastatic pattern and prognosis. We performed immunohistochemistry for cytokeratins 19 (luminal) and 14 (basal) on 92 ductal carcinoma-NST. Those tumours showing CK14 expression were further characterized by immunohistochemistry for myoepithelial cell phenotype and analysed by comparative genomic hybridization. The 7 cases of ductal carcinoma-NST exhibiting a basal cell phenotype were all grade III tumours and showed a molecular cytogenetic profile similar to more conventional myoepithelial cell carcinomas. Therefore it appears that grade III invasive ductal carcinomas contain a subset of tumours with specific morphological and cytogenetic characteristics, and probably prognosis for the patient.