It is expressed on all leukocytes but highest on thymocytes[7][8][9] and is believed to augment T-celladhesion[10][11] and apoptosis of double positive T cells.[12] It has been found in endothelial cells and in the periodontium, including gingival fibroblasts and gingival epithelial cells.[5] It also participates in migration and activation.[13] There is also experimental evidence that it binds to cyclophilin A.[14]
It is found on the cell surface of Ewing's sarcoma tumors [15] and is positive in granulosa cell tumors.[16] It is more expressed in malignant gliomas than in the brain, and such overexpression results in higher levels of invasiveness and lower rates of survival.[17] Antibodies to CD99 are used in diagnostic immunohistochemistry to distinguish Ewing's sarcoma from other tumours of similar histological appearance, as well as for the identification of thymic tumours, and of spindle cell tumours, such as synovial sarcoma, haemangiopericytoma, and meningioma.[6] EWS/FLI is thought to regulate CD99, but knockdown of EWS/FLI results in only a modest reduction in CD99. When CD99 expression is knocked down in human cells with Ewing's sarcoma and those cells are grafted onto mice, tumor and bone metastasis development is reduced.[15]
Reducing CD99 expression results in higher β-III tubulin expression and more neurite outgrowth.[15]
Upregulating CD99 expression in the cell line L428, a Hodgkin's lymphoma line, resulted in those cells redifferentiating towards B cells. Consequently, the loss of B-cell differentiation in Hodgkin's lymphoma may be due to CD99 downregulation.[18]
Men appear to express higher levels of CD99 than women.[19]
Prognostic Value
In patients with diffuse large B-cell lymphoma (DLBCL) with the germinal center B-cell (GCB, classified according to the Muris algorithm) subtype, positive expression of CD99 resulted in better 2-year event free survival (EFS) and 2-year overall survival (OS) compared to negative expression of CD99. In patients with DLBCL with non-GCB, however, negative expression of CD99 resulted in better 2-year EFS and 2-year OS.[20]
In patients with non-small cell lung cancer (NSCLC), higher CD99 expression in the stroma results in better prognosis.[21]
Interactions
There is evidence that through suppressing β1 integrin affinity, CD99 inhibits cell-extracellular matrix adhesion.[22]
^Goodfellow P, Banting G, Sheer D, Ropers HH, Caine A, Ferguson-Smith MA, Povey S, Voss R (1983). "Genetic evidence that a Y-linked gene in man is homologous to a gene on the X chromosome". Nature. 302 (5906): 346–9. Bibcode:1983Natur.302..346G. doi:10.1038/302346a0. PMID6188056. S2CID4273099.
^ abKrisanaprakornkit S, Chotjumlong P, Pata S, Chruewkamlow N, Reutrakul V, Kasinrerk W (January 2013). "CD99 ligation induces intercellular cell adhesion molecule-1 expression and secretion in human gingival fibroblasts". Arch. Oral Biol. 58 (1): 82–93. doi:10.1016/j.archoralbio.2012.06.011. PMID22795566.
^ abLeong AS-Y, Cooper K, Leong FJW-M (2003). Manual of Diagnostic Cytology (2nd ed.). Greenwich Medical Media, Ltd. pp. 145–146. ISBN 978-1-84110-100-2.
^Aussel C, Bernard G, Breittmayer JP, Pelassy C, Zoccola D, Bernard A (September 1993). "Monoclonal antibodies directed against the E2 protein (MIC2 gene product) induce exposure of phosphatidylserine at the thymocyte cell surface". Biochemistry. 32 (38): 10096–101. doi:10.1021/bi00089a027. PMID8399135.
^Kasinrerk W, Tokrasinwit N, Moonsom S, Stockinger H (January 2000). "CD99 monoclonal antibody induce homotypic adhesion of Jurkat cells through protein tyrosine kinase and protein kinase C-dependent pathway". Immunology Letters. 71 (1): 33–41. doi:10.1016/S0165-2478(99)00165-0. PMID10709783.
^Bernard G, Breittmayer JP, de Matteis M, Trampont P, Hofman P, Senik A, Bernard A (March 1997). "Apoptosis of immature thymocytes mediated by E2/CD99". Journal of Immunology. 158 (6): 2543–50. PMID9058785.
^Kim HJ, Chong KH, Kang SW, Lee JR, Kim JY, Hahn MJ, Kim TJ (September 2004). "Identification of cyclophilin A as a CD99-binding protein by yeast two-hybrid screening". Immunology Letters. 95 (2): 155–9. doi:10.1016/j.imlet.2004.07.001. PMID15388255.
^Zhou XH, Huang XP, Huang ZP, Wang ZQ, Zhao T (February 2013). "[CD99 regulates redifferentiation of classical Hodgkin's lymphoma cell line L428 towards B cells]". Nan Fang Yi Ke da Xue Xue Bao (in Chinese). 33 (2): 235–8. PMID23443779.
^Lefèvre N, Corazza F, Duchateau J, Desir J, Casimir G (July 2012). "Sex differences in inflammatory cytokines and CD99 expression following in vitro lipopolysaccharide stimulation". Shock. 38 (1): 37–42. doi:10.1097/SHK.0b013e3182571e46. PMID22575993. S2CID7092987.
^Hong J, Park S, Park J, Jang SJ, Ahn HK, Sym SJ, Cho EK, Shin DB, Lee JH (December 2012). "CD99 expression and newly diagnosed diffuse large B-cell lymphoma treated with rituximab-CHOP immunochemotherapy". Ann. Hematol. 91 (12): 1897–906. doi:10.1007/s00277-012-1533-z. PMID22864685. S2CID26024499.
^Edlund K, Lindskog C, Saito A, Berglund A, Pontén F, Göransson-Kultima H, Isaksson A, Jirström K, Planck M, Johansson L, Lambe M, Holmberg L, Nyberg F, Ekman S, Bergqvist M, Landelius P, Lamberg K, Botling J, Ostman A, Micke P (November 2012). "CD99 is a novel prognostic stromal marker in non-small cell lung cancer". Int. J. Cancer. 131 (10): 2264–73. doi:10.1002/ijc.27518. PMID22392539. S2CID10052485.
Darling SM, Goodfellow PJ, Pym B, Banting GS, Pritchard C, Goodfellow PN (1987). "Molecular genetics of MIC2: a gene shared by the human X and Y chromosomes". Cold Spring Harb. Symp. Quant. Biol. 51 (1): 205–12. doi:10.1101/SQB.1986.051.01.025. PMID3472717.
Choi EY, Park WS, Jung KC, Kim SH, Kim YY, Lee WJ, Park SH (1998). "Engagement of CD99 induces up-regulation of TCR and MHC class I and II molecules on the surface of human thymocytes". J. Immunol. 161 (2): 749–54. PMID9670951.
Gordon MD, Corless C, Renshaw AA, Beckstead J (1998). "CD99, keratin, and vimentin staining of sex cord-stromal tumors, normal ovary, and testis". Mod. Pathol. 11 (8): 769–73. PMID9720506.
Fouchet C, Gane P, Cartron JP, Lopez C (2000). "Quantitative analysis of XG blood group and CD99 antigens on human red cells". Immunogenetics. 51 (8–9): 688–94. doi:10.1007/s002510000193. PMID10941840. S2CID19170267.
Jung KC, Kim NH, Park WS, Park SH, Bae Y (2003). "The CD99 signal enhances Fas-mediated apoptosis in the human leukemic cell line, Jurkat". FEBS Lett. 554 (3): 478–84. doi:10.1016/S0014-5793(03)01224-9. PMID14623115. S2CID21588654.
Mahmood MN, Salama ME, Chaffins M, Ormsby AH, Ma CK, Linden MD, Lee MW (2004). "Solitary sclerotic fibroma of skin: a possible link with pleomorphic fibroma with immunophenotypic expression for O13 (CD99) and CD34". J. Cutan. Pathol. 30 (10): 631–6. doi:10.1034/j.1600-0560.2003.00126.x. PMID14744088. S2CID37152987.