Annexin A8 Identifies a Subpopulation of Transiently Quiescent c-Kit Positive Luminal Progenitor Cells of the Ductal Mammary Epithelium

Abstract

We have previously shown that Annexin A8 (ANXA8) is strongly associated with the basal-like subgroup of breast cancers, including BRCA1-associated breast cancers, and poor prognosis; while in the mouse mammary gland AnxA8 mRNA is expressed in low-proliferative isolated pubertal mouse mammary ductal epithelium and after enforced involution, but not in isolated highly proliferative terminal end buds (TEB) or during pregnancy. To better understand ANXA8’s association with this breast cancer subgroup we established ANXA8’s cellular distribution in the mammary gland and ANXA8’s effect on cell proliferation. We show that ANXA8 expression in the mouse mammary gland was strong during pre-puberty before the expansion of the rudimentary ductal network and was limited to a distinct subpopulation of ductal luminal epithelial cells but was not detected in TEB or in alveoli during pregnancy. Similarly, during late involution its expression was found in the surviving ductal epithelium, but not in the apoptotic alveoli. Double-immunofluorescence (IF) showed that ANXA8 positive (+ve) cells were ER-alpha negative (−ve) and mostly quiescent, as defined by lack of Ki67 expression during puberty and mid-pregnancy, but not terminally differentiated with ∼15% of ANXA8 +ve cells re-entering the cell cycle at the start of pregnancy (day 4.5). RT-PCR on RNA from FACS-sorted cells and double-IF showed that ANXA8+ve cells were a subpopulation of c-kit +ve luminal progenitor cells, which have recently been identified as the cells of origin of basal-like breast cancers. Over expression of ANXA8 in the mammary epithelial cell line Kim-2 led to a G0/G1 arrest and suppressed Ki67 expression, indicating cell cycle exit. Our data therefore identify ANXA8 as a potential mediator of quiescence in the normal mouse mammary ductal epithelium, while its expression in basal-like breast cancers may be linked to ANXA8’s association with their specific cells of origin.

Harnessing 3D models of mammary epithelial morphogenesis: An off the beaten path approach to identify candidate biomarkers of early stage breast cancer

“…Indeed, ANXA2 plays a key role in the establishment of epithelial polarity and lumenogenesis by regulating actin cytoskeleton dynamics at the apical surface of the plasma membrane and recruiting to this compartment the Cdc42 Rho-GTPase [3, 22]. Similarly, ANXA8, known to be expressed in a subset of mammary progenitor cells and upregulated during mammary gland remodeling [19, 31], is involved in the formation of endosomes [15], which are implicated in the establishment and maintenance of epithelial cell polarity [16]. …”

“…ANXA2 not only is known to be involved in the regulation of membrane dynamics and actin remodeling [17], but also plays a key role in the establishment of epithelial cell polarity and lumen formation [3, 22], two fundamental processes required for normal mammary epithelial morphogenesis. Conversely, apart from evidence of ANXA8 expression in a subpopulation of mammary progenitor cells [19] and its modulation during mouse mammary gland involution [31], less clear is the morphogenetic function of ANXA8.…”

Prognostic Value of ANXA8 in Gastric Carcinoma

“…Early research on APL identified that over-expressed ANXA8 plays a significant role in the signal transduction pathway in the APL cells [12][13][14][15]. It has been reported that ANXA8 expression is apparently upregulated in breast cancer, with a great relevance of tumor stages, grades and positive lymph nodes [17][18][19]. Of note, ANXA8 is crucial in the maintenance of the late endosomal/lysosomal compartment physiological functions in cancer cells [16] and is able to interact with phosphatidylinositides and actin-associated membrane domains [25] which are closely related to cell migration, cytokinesis, vesicle transport and cellular immunity.…”

“…Meanwhile, ANXA8 has also been linked to the formation of endosomes and epidermal growth factor receptor (EGFR) turnover in Hela cells [16]. Other reports demonstrated that the expression of ANXA8 is significantly increased in breast cancer [17][18][19], pancreatic cancer [20][21][22], ovarian cancer [23] and cholangiocarcinoma [24]. Thus, ANXA8 is expected to be a new biomarker and molecular therapeutic target for the diagnosis, treatments and prognosis of multiple diseases, especially malignant tumors.…”

Annexin A8 (ANXA8) regulates proliferation of porcine endometrial cells via Akt signalling pathway

“…Altered expression of annexin A4 is related to endometrial receptivity during the implantation window in infertile patients with endometriosis (Jiang, Li, Xing, Wang, & Feng, ). A previous study has shown that one member of annexin family, ANXA8 , has an impact on the proliferation, quiescence and colony formation in mouse mammary epithelial cells (Iglesias et al, ). The low expression of ANXA8 leads to sprouting angiogenesis, migration and adhesion deficiency (Heitzig et al, ).…”