The PAX2‐null immunophenotype defines multiple lineages with common expression signatures in benign and neoplastic oviductal epithelium

Abstract

The oviducts contain high grade serous cancer (HGSC) precursors (serous tubal intraepithelial neoplasia or STINs), which are γ-H2AXp- and TP53 mutation-positive. Although they express wild type p53, secretory cell outgrowths (SCOUTs) are associated with older age and serous cancer; moreover both STINs and SCOUTs share a loss of PAX2 expression (PAX2n). We evaluated PAX2 expression in proliferating adult and embryonic oviductal cells, normal mucosa, SCOUTs, Walthard cell nests (WCNs), STINs and HGSCs, and the expression of genes chosen empirically or from SCOUT expression arrays. Clones generated in vitro from embryonic gynecologic tract and adult fallopian tube were Krt7p/PAX2n/EZH2p and underwent ciliated (PAX2n/EZH2n/FOXJ1p) and basal (Krt7n/EZH2n/Krt5p) differentiation. Similarly non-ciliated cells in normal mucosa were PAX2p but became PAX2n in multilayered epithelium undergoing ciliated or basal (Walthard cell nests or WCN) cell differentiation. PAX2n SCOUTs fell into two groups; Type I were secretory or secretory/ciliated with a “tubal” phenotype and were ALDH1n and β-cateninmem (membraneous only). Type II displayed a columnar to pseudostratified (endometrioid) phenotype, with an EZH2p, ALDH1p, β-cateninnc (nuclear and cytoplasmic), stathminp, LEF1p, RCN1p and RUNX2p expression signature. STINs and HGSCs shared the Type I immunophenotype of PAX2n, ALDH1n, β-cateninmem, but highly expressed EZH2p, LEF1p, RCN1p, and stathminp. This study, for the first time, links PAX2n with proliferating fetal and adult oviductal cells undergoing basal and ciliated differentiation and shows that this expression state is maintained in SCOUTs, STINs and HGSCs. All three entities can demonstrate a consistent perturbation of genes involved in potential tumor suppressor gene silencing (EZH2), transcriptional regulation (LEF1), regulation of differentiation (RUNX2), calcium binding (RCN1) and oncogenesis (stathmin). This shared expression signature between benign and neoplastic entities links normal progenitor cell expansion to abnormal and neoplastic outgrowth in the oviduct and exposes a common pathway that could be a target for early prevention.

The conceptual advances of carcinogenic sequence model in high-grade serous ovarian cancer

“…Non-ciliated cells, such as secretory cells, in normal fallopian tubal epithelium were PAX2-positive, but ciliated cells were PAX2-negative (25). The protein encoded by the PAX2 gene induces epithelial invagination to form a tubular structure in Müllerian duct precursors of the coelomic epithelium.…”

“…However, a small proportion of SCOUT is identified by p53+ and p73+ in fallopian tubes from women with inheri ted and sporadic HGSC (5). SCOUT, p53 signature, STIC and HGSC share a positive staining for STMN1 and EZH2 and negative staining for PAX2 (25). P53 signature, STIC and HGSC exhibit a negative staining for ALDH1A1 (31).…”

“…A member of the PAX family, PAX8, also plays a role in organogenesis of the Müllerian system and is a marker of fallopian tubal secretory cells and ovarian surface epithelium (OSE) (16,27). Other molecular characteristics identified in fallopian tube epithelium are as follows: Fallopian tubal epithelium comprises different phenotypic and molecular subtypes; secretory cells (BCL2+, PAX2+, PAX8+, HMFG2+, p73-, FOXJ1-, and acety lated tubulin-) and cilia ted cells (BCL2-, PAX2-, PAX8-, HMFG2-, p73+, FOXJ1+, LhS28+, acetylated tubulin+, and Sall2+) (16,(25)(26)(27). p73 is a homologue of the p53 and induces cell cycle arrest, conferring its tumor suppressive activity.…”

“…This lesion is identified by BCL2+, STMN1+, EZH2+, p53-, p73-, PAX2-, PAX8-, MIB1-, ALDH1A1-, and γ-H2AX- (5,13,25,31). The majority of SCOUT is typically associated with wild-type p53 expression (do not overexpress p53) and a loss of PAX2 and p73 expression (13,25). SCOUT may be a non-obligate precursor of HGSC.…”

“…Investigators have characterized the stepwise changes of molecular profiles identified by genomic, proteomic and immunohistochemical approaches, including BCL2 (BCL2 apoptosis regulator), p73 (tumor protein p73), PAX2 (paired box 2), p53, PAX8 (paired box 8), H2AX (H2A histone family member X), STMN1 (stathmin 1), EZH2 (enhancer of zeste 2 polycomb repressive complex 2 subunit), Ki67, ALDH1A1 (aldehyde dehydrogenase 1 family member A1), CTNNB1 (β-catenin), CCNE1 (cyclin E1), LAMC1 (Laminin γ1), and HMGA2 (high mobility group AT-hook 2) genes and telomere shortening (Table I) (3,5,12,13,16,(25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35)(36)(37).…”