Total HLA class I loss in a sarcomatoid renal carcinoma cell line caused by the coexistence of distinct mutations in the two encoding β2-microglobulin genes

Abstract

In renal cell carcinoma (RCC), HLA class I downregulation has been found in about 40% of the lesions examined. Since only scanty information is available about the molecular basis of these defects, we have investigated the mechanism(s) underlying HLA class I antigen down-regulation or loss in six RCC cell lines. Five of them express HLA class I antigens although at various levels; on the other hand, HLA class I antigens are not detectable on the remaining cell line, the RCC52 cell line, belonging to a sarcomatoid subtype, even following incubation with IFN-γ. β 2 -microglobulin (β 2 m) was not detected in RCC52 cells. Surprisingly, RCC52 cells harbor two mutations in the β 2 m genes in exon 1: a single G deletion (delG) in codon 6, which introduces a premature stop at codon 7, and a CT dinucleotide deletion (delCT), which leads to a premature stop at codon 55. Analysis of eight clonal sublines isolated from the RCC52 cell line showed that the two β 2 m gene mutations are carried separately by RCC52 cell subpopulations. The delG/delCT double mutations were detected in two sublines with a fibroblast-like morphology, while the delCT mutation was detected in the remaining six sublines with an epithelial cell morphology. Furthermore, loss of heterozygosity (LOH) of the β 2 m gene at STR D15S-209 was found only in the epithelioid subpopulation, indicating loss of one copy of chromosome 15. Immunostaining results of the tumor lesion from which the cell line RCC52 was originated were consistent with the phenotyping/ molecular findings of the cultured cells. This is the first example of the coexistence of distinct β 2 m defects in two different tumor subpopulations of a RCC, where loss of one copy of chromosome 15 occurs in one of the subpopulations with total HLA class I antigen loss.

Differential expression of CD44 and CD24 markers discriminates the epitheliod from the fibroblastoid subset in a sarcomatoid renal carcinoma cell line: evidence suggesting the existence of cancer stem cells in both subsets as studied with sorted cells

“…In line with our previous observations [28, 29], HLA class I was not detected on the cell surface or in the cytoplasm of either CD44/CD24 sorted cells. Moreover, surface E-cadherin was detected in the CD44 bright /CD24 dim sorted but not in the CD44 bright /CD24 bright sorted cells.…”

“…Their origins, sources and characteristics were previously described [28, 29]. All the cell lines were maintained in RPMI-1640 medium (Gibco, Grand Island, NY), containing 2 mM L-glutamine, 100 units/ml penicillin, 100 μg/ml streptomycin, 1 mM sodium private and 10% FBS which had been previously heat-inactivated at 56°C for 30 min.…”

Bare lymphocyte syndrome: An opportunity to discover our immune system

“…In addition, some of the immunological abnormalities in CVID match those of the BLS syndrome, like loss of B cell-T cell interaction, defective germinal center response, hypogammaglobulinemia, etc., and the possibility for these cases cannot be ruled out until the archives of CVID are not screened [144]. Cancers due to the loss or mutation of ␤2M are also reported but no such mutations are defined for BLS disease [145][146][147]. Similarly, squamous cell carcinoma in a TAP2 deficient patient has raised a serious question about the risk linked to MHC deficiency [40].…”

Immunotherapy of cancer is a part of biotherapy

“…In other words, its tumor killing should be effective for patients in whom the surface HLA-class I expression on cancer cells was deficient or lost [22,23] , or whose tumors were drug-resistant [24] , as long as the patient's tumor cells could all be detected by the CAR-T cells to be infused [24,25] . It is well known that the expression of HLA class I in cancer cells of patients with the advanced stage or under the influence of treatment tends to become deficient or lost totally [22,23,26] , one way for tumor cells to escape from the host immune surveillance. Of note, these modes of adoptive cell transfer are considered personalized immunotherapies, as patients' own immune cells are processed, expanded, and infused back to the individual patients.…”