[CD5-positive diffuse large B-cell lymphoma with gastrointestinal infiltration presenting with protein-losing enteropathy].

Protein-losing enteropathy is rarely associated with malignant lymphoma. This report describes the case of a 67-year-old man with diffuse large B-cell lymphoma (DLBCL) and concomitant protein-losing enteropathy who was admitted to our hospital for evaluation of watery diarrhea, edema, and abdominal fullness. On admission, the patient reported a history of weight gain. Subsequent examination showed ascites, hepatosplenomegaly, and hypoalbuminemia. Notably, 99mTc-labeled human serum albumin scintigraphy revealed protein loss from the intestine, and the patient was diagnosed with protein-losing enteropathy. Endoscopy revealed erosive and edematous hyperplasia of the gastric-colonic mucosa, and histopathological evaluation of a biopsy specimen showed proliferation of CD20+ and CD5+ tumor cells. Thus, the diagnosis of DLBCL was histopathologically confirmed. Lymphomatous infiltration of the bone marrow was observed; however, no lymphadenopathy was detected. Based on these findings, the patient was diagnosed with protein-losing enteropathy associated with gastrointestinal infiltration of CD5+ DLBCL. Hypoalbuminemia and diarrhea improved following the initiation of R-CHOP regimen. The DLBCL showed a favorable response to treatment, and gastrointestinal lesions and hepatosplenomegaly improved, along with the resolution of protein-losing enteropathy.

Glycosylation Status of CD43 Protein Is Associated with Resistance of Leukemia Cells to CTL-Mediated Cytolysis.

To improve cancer immunotherapy, it is important to understand how tumor cells counteract immune-surveillance. In this study, we sought to identify cell-surface molecules associated with resistance of leukemia cells to cytotoxic T cell (CTL)-mediated cytolysis. To this end, we first established thousands of monoclonal antibodies (mAbs) that react with MLL/AF9 mouse leukemia cells. Only two of these mAbs, designated R54 and B2, bound preferentially to leukemia cells resistant to cytolysis by a tumor cell antigen-specific CTLs. The antigens recognized by these mAbs were identified by expression cloning as the same protein, CD43, although their binding patterns to subsets of hematopoietic cells differed significantly from each other and from a pre-existing pan-CD43 mAb, S11. The epitopes of R54 and B2, but not S11, were sialidase-sensitive and expressed at various levels on leukemia cells, suggesting that binding of R54 or B2 is associated with the glycosylation status of CD43. R54high leukemia cells, which are likely to express sialic acid-rich CD43, were highly resistant to CTL-mediated cytolysis. In addition, loss of CD43 in leukemia cells or neuraminidase treatment of leukemia cells sensitized leukemia cells to CTL-mediated cell lysis. These results suggest that sialic acid-rich CD43, which harbors multiple sialic acid residues that impart a net negative surface charge, protects leukemia cells from CTL-mediated cell lysis. Furthermore, R54high or B2high leukemia cells preferentially survived in vivo in the presence of adaptive immunity. Taken together, these results suggest that the glycosylation status of CD43 on leukemia is associated with sensitivity to CTL-mediated cytolysis in vitro and in vivo. Thus, regulation of CD43 glycosylation is a potential strategy for enhancing CTL-mediated immunotherapy.