Serum Prolactin Contributes to Enhancing Prolactin Receptor and pJAK2 in Type I Endometrial Cancer Cells in Young Women Without Insulin Resistance

Endometrial cancer with a POLE mutation progresses frequently through the type I pathway despite its high-grade endometrioid morphology: a cohort study at a single institution in Japan

POLE-mutated endometrial cancer (EC) frequently shows high-grade endometrioid histology, which represents heterogeneity in the dualistic classification of EC. This study aimed to assess the clinicopathology and pathogenesis of POLE-mutated EC due to the scarcity of related information for Asian women. POLE variants were sequenced in tissues of Japanese women with EC. The tumor mutation burden (TMB) was assessed in tissues with a POLE variant of unknown significance. In the POLE-mutated EC tissues, the immunostaining expression of CD8, hormonal receptors, and p53 was evaluated, and the POLE variants in cancer and atypical endometrial hyperplasia (AEH) lesions were assessed by laser-capture microdissection. POLE variants were identified in five patients (3.9%) with high-grade endometrioid carcinoma among 127 patients with EC (S459F in two tissues and P441P in three tissues with a high TMB). The five cancer tissues coexisted with normal endometrium and/or AEH. Both AEH and cancer cells showed hormonal receptor positivity and harbored the same POLE mutation. Two patients showed a subclonal overexpression pattern of p53 in cancer and AEH lesions. In conclusion, POLE-mutated EC progresses through the type I pathway, even though it frequently shows high-grade endometrioid morphology. The common POLE mutation sites in EC might vary among races.

The Relevant Participation of Prolactin in the Genesis and Progression of Gynecological Cancers

Prolactin (PRL) is a hormone produced by the pituitary gland and multiple non-pituitary sites, vital in several physiological processes such as lactation, pregnancy, cell growth, and differentiation. However, PRL is nowadays known to have a strong implication in oncogenic processes, making it essential to delve into the mechanisms governing these actions. PRL and its receptor (PRLR) activate a series of effects such as survival, cellular proliferation, migration, invasion, metastasis, and resistance to treatment, being highly relevant in developing certain types of cancer. Because women produce high levels of PRL, its influence in gynecological cancers is herein reviewed. It is interesting that, other than the 23 kDa PRL, whose mechanism of action is endocrine, other variants of PRL have been observed to be produced by tumoral tissue, acting in a paracrine/autocrine manner. Because many components, including PRL, surround the microenvironment, it is interesting to understand the hormone's modulation in cancer cells. This work aims to review the most important findings regarding the PRL/PRLR axis in cervical, ovarian, and endometrial cancers and its molecular mechanisms to support carcinogenesis.

Prolactin Enhances the Proliferation of Proliferative Endometrial Glandular Cells and Endometrial Cancer Cells

To elucidate the mechanism of endometrial cancer (EC) development in young hyperprolactinemic women, this study assessed the hormonal receptor expression, proliferation, and signaling induced by prolactin in endometrial glands (EG) and EC. Prolactin receptor (PRLR) and estrogen receptor alpha (ER-α) in EG were evaluated during the menstrual cycle by immunohistochemistry. The following parameters were compared between EM-E6/E7/TERT cells, which originated from proliferative EG and Ishikawa cells. The expression levels of PRLR, pJAK2 (phosphorylated Janus Activating Kinase 2), its downstream pathways (MAPK, PI3K, and STAT), and ER-α were assessed after adding prolactin by Western blotting. U0126 was used as a MAPK inhibitor. The proliferation caused by estradiol was also examined by MTS assay after adding prolactin. PRLR expression in the EG was significantly higher in the proliferative phase than in the secretory phase, and it was correlated with ER-α expression during the menstrual cycle. After adding prolactin, the expression of pJAK2, PRLR and ER-α was significantly increased in both cell lines, MAPK was activated after adding prolactin in both cell lines, and PI3K and STAT were activated only in EM-E6/E7/TERT cells. The increased proliferation induced by estradiol was enhanced after adding prolactin in both cell lines. All changes caused by prolactin were inhibited in Ishikawa cells pretreated with U0126. Long-term effects of serum prolactin on persistent proliferative endometrium in the presence of estradiol may induce abnormal proliferation of EG in hyperprolactinemic women. Prolactin-PRLR signaling via MAPK may play a crucial role in the progression of EC in hyperprolactinemic women.