Epigenetics of Endocrine Tumors in Women and Dietary Prevention

Endocrine tumors, primarily breast, followed by uterine, ovarian, and cervical cancer, are frequent malignancies in women (Fig. 9.1). The development of these tumors can be linked to activation of oncogenes whose protein products contribute to stimulation of cancer processes such as cell proliferation, inflammation, invasion, angiogenesis, and metastasis; and/or inactivation of tumor suppressor genes which oppose the function of oncogenes and encode for proteins that inhibit cell proliferation, regulate DNA repair, and induce apoptosis. According to the Knudson “two-hits” hypothesis, hereditary cancers result from inherited gene mutations (first hit) in one copy of a cancer susceptibility gene (Fig. 9.2a). This is also referred to as haploinsufficiency when a single-copy loss in a tumor suppressor gene is sufficient for promotion of cancer. The second allele (second hit) is usually inactivated somatically (loss of heterozygosity) during growth and development (http://www.cancer.org). Interestingly, only a small fraction (5–10 %) of cancers is linked to germline mutations of tumor suppressor genes and tends to occur early in life. Examples of tumor suppressor genes mutated in hereditary cancers are Rb, p53, Apc, BRCA-1, and BRCA-2. This scenario differs from that of sporadic tumors which represent the majority of tumors. They usually occur later in life in the context of other genetic and/or environmental insults (Nature 476:163–9, 2011) and when both alleles for a specific tumor suppressor gene are somatically inactivated. Therefore, understanding the mechanisms that lead to somatic inactivation of tumor suppressor genes provides rich opportunities for prevention of both hereditary and sporadic tumors including endocrine malignancies in women.