The structure-function relationships of insulin-like growth factor 1 Ec in C2C12 cells

Insulin-like growth factor 1 (IGF1) is a crucial growth factor, that regulates skeletal muscles development during cell growth and repair. Recently, its alternative splicing variant, named IGF1Ec, also named mechano-growth factor (MGF), has gained attentions as a new damage repair factor. However, the structure-function relationships of IGF1Ec have not been fully clarified due to contradictory reports. In this study, we systematically investigated physiologic responses of C2C12 muscle cells to IGF1Ec, IGF1 and MGF E peptide. Our data indicate that while the N-terminal sequence of IGF1Ec, which is homolog in part with IGF1, promotes proliferation; the C-terminal sequence of IGF1Ec, which is identical to MGF E, promotes differentiation and migration of C2C12 cells. Our results suggest that MGF E cannot completely replace all the functions of IGF1Ec on muscle repair and regeneration, and elucidate the relationships between structure and function of IGF1Ec.

IGF-IEc expression is associated with advanced clinical and pathological stage of prostate cancer

BACKGROUND

Recent evidence suggests a role for the insulin-like growth factor-1Ec (IGF-IEc) transcript variant in cancer biology. The aim of the present study was to investigate whether IGF-IEc expression is associated with prostate cancer stage.

MATERIALS AND METHODS

Formalin-fixed and paraffin-embedded prostate cancer surgical specimens from 83 patients were assessed by immunohistochemistry for IGF-IEc expression.

RESULTS

Normal prostate epithelium was negative or demonstrated mild IGF-IEc cytoplasmic expression whereas prostate cancer exhibited mild to strong cytoplasmic immunoexpression. The mean IGF-1Ec expression, was significantly lower (p=0.004) in localized (stage ≤ IIb) prostate cancer, compared to locally advanced tumors (stage ≥ III). Only one out of 83 (1.2%) prostate cancer samples was completely negative for IGF-IEc. A weak-positive correlation was also observed between IGF-IEc expression levels and Gleason score (r=0.247; p=0.024).

CONCLUSION

The present data demonstrate that the expression of IGF-IEc is positively-associated with more advanced stage and higher Gleason score of prostate carcinomas.