Declining melatonin levels and MT1 receptor expression in aging rats is associated with enhanced mammary tumor growth and decreased sensitivity to melatonin

Published on Thursday, 09 July 2015


Serum melatonin (MLT) levels have been reported to diminish significantly by the 5th and 6th decades of life as the incidence of breast cancer increases.

Given MLT's anti-cancer activity, we hypothesize that age-related decline in pineal MLT production leads to enhanced breast cancer development and growth as women age.

In this study, we sought to determine whether the growth of tissue-isolated mammary tumors in young, adult, and old female Buffalo rats relates to the age-related changes in MLT and its MT1 receptor.

Significant decreases in the peak nighttime serum MLT levels were observed in old as compared to adult and young rats. Significantly diminished nighttime and early morning levels of MT1-melatonin receptors were observed in uteri from old rats compared to adult and young rats.

Growth rates in transplanted, tissue-isolated, carcinogen-induced mammary tumors are significantly increased in old rats as compared to adult or young rats. The growth-suppressive actions of exogenous MLT are diminished in old rats compared to adult and young rats.

This decrease in tumor response correlates with reduced expression of the MT1 receptor in old as compared to young and adult rats. Thus, enhanced mammary tumor growth is associated with old age and diminished levels of MLT and MT1 receptor during old age, resulting in reduced sensitivity to exogenous MLT.

Finally, our studies demonstrate that the tissue-isolated tumor model is viable model system in which to study the role of aging on breast cancer growth.



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See also:

- About Melatonin;

- Evaluation of the safety and efficacy of the first-line treatment with somatostatin combined with melatonisn, retinoids, vitamin D3, and low doses of cyclophosphamide in 20 cases of breast cancer: a preliminary report;

- The Di Bella Method (DBM) improved survival, objective response and performance status in a retrospective observational clinical study on 122 cases of breast cancer;

- Complete objective response to biological therapy of plurifocal breast carcinoma.