A New Antigen Recognized by Cytolytic T Lymphocytes on a Human Kidney Tumor Results from Reverse Strand Transcription

Abstract

By stimulating blood lymphocytes from a renal cell carcinoma patient in vitro with the autologous tumor cells, we obtained cytolytic T lymphocyte (CTL) clones that killed several autologous and allogeneic histocompatibility leukocyte antigen (HLA)-B7 renal carcinoma cell lines. We identified the target antigen of these CTLs by screening COS cells transfected with the HLA-B7 cDNA and with a cDNA library prepared with RNA from the tumor cells. The antigenic peptide recognized by the CTLs has the sequence LPRWPPPQL and is encoded by a new gene, which we named RU2. This gene is transcribed in both directions. The antigenic peptide is not encoded by the sense transcript, RU2S, which is expressed ubiquitously. It is encoded by an antisense transcript, RU2AS, which starts from a cryptic promoter located on the reverse strand of the first intron and ends up on the reverse strand of the RU2S promoter, which contains a polyadenylation signal. This mechanism of antigen expression is unprecedented and further illustrates the notion that many peptides recognized by T cells cannot be predicted from the primary structure of the major product of the encoding gene. Antisense transcript RU2AS is expressed in a high proportion of tumors of various histological types. It is absent in most normal tissues, but is expressed in testis and kidney, and, at lower levels, in urinary bladder and liver. Short-term cultures of normal epithelial cells from the renal proximal tubule expressed significant levels of RU2AS message and were recognized by the CTLs. Therefore, this antigen is not tumor specific, but corresponds to a self-antigen with restricted tissue distribution.

Evidence of graft-versus-tumour effect following allogeneic haematopoietic stem cell transplantation in renal cancer other than clear cell type

“…1 Main evidence of the potency of GVT effect is represented by sustained remissions obtained after NST in patients with metastatic renal cell carcinoma (RCC) refractory to conventional cytokine-based immunotherapy. 2,3 This evidence supports the notion that RCC harbours immunogenic peculiarities [4][5][6] that render this tumour responsive to immunotherapies. 7 Interestingly, only clear cell carcinoma, but not other RCC histotypes, has been reported to respond to NST.…”

LUCA-15-encoded sequence variants regulate CD95-mediated apoptosis

“…Indeed, while once thought to exist only in the realm of viral regulation of host gene expression, it now appears that antisense regulation is a far more widespread mechanism of cellular control, involving both antisense mRNA and protein (Van Den Eynde et al, 1999). One well characterized example is very similar to the case described here for LUCA-15, in which the 3'-UTRs of two genes from C. elegans, Lin-14 and Lin-28, contain conserved sequences that are antisense to the RNA of a third gene, Lin-4 (Moss et al, 1997;Wightman et al, 1993;Lee et al, 1993).…”

Immunity to melanoma: unraveling the relation of tumor immunity and autoimmunity

“…Boon et al, more than a decade ago, described that a nucleotide point mutation encoding a single amino-acid change could be recognized by CD8+lymphocytes through enhanced binding to MHC (Lurquin et al, 1989). Furthermore, it has recently been established that the immune system can recognize products of alternative transcripts from cryptic start sites, alternative splicing, novel open reading frames, pseudogenes (Moreau-Aubry et al, 2000) and even products of antisense strands of DNA (Van Den Eynde et al, 1999).…”