Characterization of the expression of HTm4 (MS4A3), a cell cycle regulator, in human peripheral blood cells and normal and malignant tissues.
Bottom Line: Early reports demonstrated that HTm4 is largely restricted to the haematopoietic lineage, and is involved in cell cycle control, via a regulatory interaction with the kinase-associated phosphatase, cyclin A and cyclin-dependent kinase 2 (CDK2).Very weak HTm4 expression is found in monocytes, granulocytes and B cells, but not in T cells, by lineage specific haematopoietic cell flow cytometry analysis.Malignant tissue microarray analysis showed HTm4 expression in a wide variety of adenocarcinomas, including breast, prostate and ovarian.
Affiliation: Harvard Medical School, Department of Pathology, Brigham and Women's Hospital, Boston, MA 02115, USA.Show MeSH
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Mentions: Immunohistochemical studies on normal human tissue microarrays were performed to evaluate for HTm4 expression. Both the immunoreactive cell type and the intensity of staining were noted and are detailed in Table 1. In general, HTm4 expression was restricted to a limited number of cell types including subset of leucocytes (primarily macrophages) in nodal and splenic tissues, and, in addition, small numbers of cell types in some non-haematopoietic tissues including ductal epithelium of the breast, testis (seminiferous tubules and rete), pancreas, prostate, stomach, thymus and the haematopoietic cells within foetal liver (Fig. 6A–I). The strong staining of immature haematolymphoid cells in the foetal liver (Fig. 6I) and cortical lymphoblasts of the thymus (Fig. 6J) are in keeping with a role for HTm4 in haematopoietic cell development. Absent staining was observed in thyroid, oesophagus, small bowel, colon (Fig. 6J), gallbladder, kidney, heart, skin or aorta. Control immunoglobulin staining failed to show any reactivity with these tissues (data not shown). As we have previously reported, germinal centre B cells within secondary follicles also showed HTm4 expression . Interestingly, adult brain also showed moderate levels of HTm4 expression in focal glial elements and neurons (Table 1), but to a lesser extent than in the foetal brain, in keeping with the weak level of expression noted in the Western blot in foetal brain and inability to detect the protein in adult brain (Fig. 4).
Affiliation: Harvard Medical School, Department of Pathology, Brigham and Women's Hospital, Boston, MA 02115, USA.