Histopathological analysis potential for unveiling hormone signaling in endocrine-related tumors.

Elucidating the mechanisms of action of steroid hormones will contribute to the development of therapeutic strategies for hormone-dependent tumors. Recent advances in genetic engineering have revealed the complex and diverse mechanisms of steroid hormone signaling; however, these techniques are limited to in vitro or animal experiments. It is believed that verifying hormone signals elucidated using human pathological tissue specimens will directly aid in treatment and diagnosis. However, pathological tissue specimens are generally formalin-fixed paraffin-embedded (FFPE), and protein/gene analyses of FFPE tissues are limited. Protein detection using immunohistochemistry with specific antibodies in FFPE tissues is a classical technique essential for diagnosis and treatment decisions in various types of cancer. In steroid hormone signaling, the expression and localization of receptors, hormone-related enzymes, and proteins encoded by response genes can be clarified using immunohistochemistry. Although protein-protein interactions such as receptor dimers and DNA-binding proteins are mainly detected in vitro, they can be examined in FFPE tissues using in situ proximity ligation assays and southwestern histochemistry, respectively. Using these detection methods, including immunohistochemistry, it is possible to analyze each hormone signaling pathway in hormone-related tumors histopathologically. Although FFPE tissues still suffer from gene and protein denaturation, their advantages include the ability to retrospectively study target factors/signals and obtain spatial information through microscopy. This review describes a visualization method for elucidating steroid hormone signaling in hormone-dependent tumors using FFPE tissues.