Nuclear factor-κB2 represses Sp1-mediated transcription at the CD99 promoter

Morphologic and immunophenotypical features distinguishing Merkel cell polyomavirus-positive and negative Merkel cell carcinoma

In 2008, Feng et al. identified Merkel cell polyomavirus integration as the primary oncogenic event in ~80% of Merkel cell carcinoma cases. The remaining virus-negative Merkel cell carcinoma cases associated with a high mutational load are most likely caused by UV radiation. The current study aimed to compare the morphological and immunohistochemical features of 80 virus-positive and 21 virus-negative Merkel cell carcinoma cases. Microscopic evaluation revealed that elongated nuclei-similar to the spindle-shape variant of small cell lung cancer-were less frequent in Merkel cell polyomavirus-positive Merkel cell carcinoma compared to the virus-negative subset (p = 0.005). Moreover, virus-negative cases more frequently displayed a "large-cell neuroendocrine carcinoma" phenotype with larger cell size (p = 0.0026), abundant cytoplasm (p = 4×10^-7) and prominent nucleoli (p = 0.002). Analysis of immunohistochemical data revealed frequent positivity for thyroid transcription factor 1 and cytokeratin 7, either absence or overexpression of p53, as well as frequent lack of neurofilament expression in virus-negative cases. By contrast, cytokeratin 8, 18 and 20 and a CD99 with a dot pattern as well as high EMA expression were identified as characteristic features of virus-positive Merkel cell carcinoma. In particular, the CD99 dot-like expression pattern was strongly associated with presence of the Merkel cell polyomavirus in Merkel cell carcinoma (sensitivity = 81%, specificity = 90%, positive likelihood ratio = 8.08). To conclude, virus-positive and -negative Merkel cell carcinoma are characterized by distinct morphological and immunohistochemical features, which implies a significant difference in tumor biology and behavior. Importantly, we identified the CD99 staining pattern as a marker indicating the virus status of this skin cancer.

NFκB2 p52 stabilizes rhogdiβ mRNA by inhibiting AUF1 protein degradation via a miR-145/Sp1/USP8-dependent axis

Although overexpression of the non-canonical NFκB subunit p52 has been observed in several tumors, the function and mechanism of p52 in bladder cancer (BC) are less well understood. Here, we aimed at understanding the role and mechanism underlying p52 regulation of BC invasion. Human p52 was stably knockdown with shRNA targeting p52 in two bladder cancer cell lines (T24 and UMUC3). Two constitutively expressing constructs, p52 and p100, were stably transfected in to T24 or UMUC3, respectively. The stable transfectants were used to determine function and mechanisms responsible for p52 regulation of BC invasion. We demonstrate that p52 mediates human BC invasion. Knockdown of p52 impaired bladder cancer invasion by reduction of rhogdiβ mRNA stability and expression. Positively regulation of rhogdiβ mRNA stability was mediated by p52 promoting AUF1 protein degradation, consequently resulting in reduction of AUF1 binding to rhogdiβ mRNA. Further studies indicated that AUF1 protein degradation was mediated by upregulating USP8 transcription, which was modulated by its negative regulatory transcription factor Sp1. Moreover, we found that p52 upregulated miR-145, which directly bound to the 3'-UTR of sp1 mRNA, leading to downregulation of Sp1 protein translation. Our results reveal a comprehensive pathway that p52 acts as a positive regulator of BC invasion by initiating a novel miR-145/Sp1/USP8/AUF1/RhoGDIβ axis. These findings provide insight into the understanding of p52 in the pathology of human BC invasion and progression, which may be useful information in the development of preventive and therapeutic approaches for using p52 as a potential target.

CD99 at the crossroads of physiology and pathology

CD99 is a cell surface protein with unique features and only partly defined mechanisms of action. This molecule is involved in crucial biological processes, including cell adhesion, migration, death, differentiation and diapedesis, and it influences processes associated with inflammation, immune responses and cancer. CD99 is frequently overexpressed in many types of tumors, particularly pediatric tumors including Ewing sarcoma and specific subtypes of leukemia. Engagement of CD99 induces the death of malignant cells through non-conventional mechanisms. In Ewing sarcoma, triggering of CD99 by specific monoclonal antibodies activates hyperstimulation of micropinocytosis and leads to cancer cells killing through a caspase-independent, non-apoptotic pathway resembling methuosis. This process is characterized by extreme accumulation of vacuoles in the cytoplasmic space, which compromises cell viability, requires the activation of RAS-Rac1 downstream signaling and appears to be rather specific for tumor cells. In addition, anti-CD99 monoclonal antibodies exhibit antitumor activities in xenografts in the absence of immune effector cells or complement proteins. Overall, these data establish CD99 as a new opportunity to treat patients with high expression of CD99, particularly those that are resistant to canonical apoptosis-inducing agents.

CD99 refers to the activity of inflammatory bowel disease

BACKGROUND

Inflammatory bowel disease (IBD), composed of Crohn's disease (CD) and ulcerative colitis (UC), is an inflammatory autoimmune disease. CD99 has been reported to participate in migration of leukocytes and T cell activation. However, the roles of CD99 in IBD are obscure.

MATERIALS AND METHODS

CD99 expression was examined in peripheral blood mononuclear cells (PBMCs) and inflamed mucosa from IBD patients by qRT-PCR. Serum TNF-α and IL-17A levels were detected by ELISA. Correlations of CD99 expression with TNF-α, IL-17A, Crohn's disease activity index (CDAI), simple endoscopic score for CD (SES-CD), Mayo index, and Truelove grading were performed by Pearson's correlation.

RESULTS

CD99 expression was increased in PBMCs and inflamed mucosa from active CD and UC patients, and CD99 expression was also increased in the inflamed mucosa compared with unaffected control from the same patients. Serum TNF-α and IL-17A levels were increased in active CD or UC patients, and positively correlated with CD99 expression in PBMCs (CD: r = .402, p = .009; r = .350, p = .025. UC: r = .289, p = .028; r = .322, p = .014). Moreover, CD99 expression in inflamed mucosa was correlated with CDAI, SES-CD, Mayo index, and Truelove grading (r = .410, p = .012; r = .341, p = .005; r = .366, p = .002; r = .312, p = .011).

CONCLUSION

CD99 expression is increased in patients with active IBD, and positively correlated with disease activity. Therefore, CD99 expression can be used as an index to evaluate the activity of IBD.

CD99-dependent expansion of myeloid-derived suppressor cells and attenuation of graft-versus-host disease

CD99 is involved in many cellular events, such as the generation of Hodgkin and Reed-Sternberg cells, T cell costimulation, and leukocyte transendothelial migration. However, these studies have been limited to in vitro or in vivo experiments using CD99-deficient cell lines or anti-CD99 antibodies. In the present study, using CD99-deficient mice established by the exchangeable gene trap method, we investigated the physiologic function of murine CD99. In a B6 splenocytes → bm12 graft-versus-host disease model, wild-type cells were minimally lethal, whereas all mice that received CD99-deficient donor cells developed an early and more severe pathology. Graftversus-host disease in these mice was associated with insufficient expansion of myeloid-derived suppressor cells. This was confirmed by experiments illustrating that the injection of wild-type donor cells depleted of Mac-1(+) cells led to an almost identical disease course as the CD99-deficient donor system. Therefore, these results suggest that CD99 plays a crucial role in the attenuation of graft-versus-host disease by regulating the expansion of myeloid-derived suppressor cells.