Expression patterns of HDAC6 in correlation to ARID1A status in different subtypes of endometriosis: A retrospective tissue microarray analysis

Endometriosis is a disease affecting approximately 10% of reproductive age women. Loss of the tumor suppressor gene AT-rich interactive domain-containing protein 1A (ARID1A) occurs in some endometriosis cases. Histone deacetylase 6 (HDAC-6) is an enzyme with implication in several diseases including different cancer types and immunological disorders, where it is involved in protein trafficking and degradation, cell shape, and migration. In ARID1A-deficient ovarian cancer increased HDAC-6 expression lead to apoptosis-inhibiting post-translational modification of p53. It is not known if HDAC-6 expression is also altered in ARID1A-deficient endometriosis. The aim of this study was to assess HDAC-6 expression in endometriotic lesions in correlation to ARID1A-status. Two tissue-microarrays with 168 endometriotic lesions, including ovarian (64/168, 38 %), peritoneal (66/ 168, 39 %) and deep-infiltrating (38/168, 23 %) subtypes, and 73 endometrium of women without endometriosis were assessed. Mean ARID1A immunoreactivity score (IRS) in endometriosis group was 10.83 (+2.36) and 10.78 (+1.94) in the epithelium and stroma, respectively, while the respective mean HDAC6 IRS were 9.16 (+2.76) and 5.94 (+2.88). The comparison of the HDAC6 expression between endometriosis subtypes showed higher expression in deep-infiltrating endometriosis, in both, epithelium (p = 0.032) and stroma (p = 0.007). In ARID1A negative cases, epithelial expression of HDAC6 was higher in endometriosis compared to women without endometriosis (p = 0.031), and this was also specifically observed in the subset of ovarian endometriosis (p = 0.037). There were no significant differences in the stromal expression of HDAC6. In conclusion, our results demonstrate a complex expression pattern of HDAC6 depending on ARID1A status in different endometriosis subtypes. Further studies on HDAC6 and ARID1A are important to elucidate mechanisms involved in malignant transformation of endometriosis.