A novel diffuse large B-cell lymphoma-associated cancer testis antigen encoding a PAS domain protein

Abstract

Here we report that the OX-TES-1 SEREX antigen, which showed immunological reactivity with serum from four out of 10 diffuse large B-cell lymphoma (DLBCL) patients, is encoded by a novel gene, PAS domain containing 1 (PASD1). PASD1_v1 cDNA encodes a 639 amino-acid (aa) protein product, while an alternatively spliced variant (PASD1_v2), lacking intron 14, encodes a 773 aa protein, the first 638 aa of which are common to both proteins. The PASD1-predicted protein contains a PAS domain that, together with a putative leucine zipper and nuclear localisation signal, suggests it encodes a transcription factor. The expression of PASD1_v1 mRNA was confirmed by RT -PCR in seven DLBCL-derived cell lines, while PASD1_v2 mRNA appears to be preferentially expressed in cell lines derived from non-germinal centre DLBCL. Immunophenotyping studies of de novo DLBCL patients' tumours with antibodies to CD10, BCL-6 and MUM1 indicated that two patients mounting an immune response to PASD1 were of a poor prognosis nongerminal centre subtype. Expression of PASD1 mRNA was restricted to normal testis, while frequent expression was observed in solid tumours (25 out of 68), thus fulfilling the criteria for a novel cancer testis antigen. PASD1 has potential for lymphoma vaccine development that may also be widely applicable to other tumour types.

PASD1, a DLBCL-associated cancer testis antigen and candidate for lymphoma immunotherapy

“…2 Significantly, PASD1 was also detected in a range of other B-and T-cell malignancies (Table 1). Antibody PASD1-1 stained more tumors than antibody PASD1-2, and PASD1 expression in these tumors was predominantly cytoplasmic rather than nuclear suggesting the presence of PASD1 proteins other than PASD1_v2.…”

“…Their restricted normal tissue expression, commonly widespread expression in tumors and immunogenicity makes them attractive therapeutic targets and markers for early diagnosis of cancer. 1 We originally identified per ARNT SIM (PAS) domain containing 1 (PASD1) protein as a TAA in DLBCL 2 and acute myeloid leukemia (AML). 3 Circulating antibodies to this putative transcription factor were present in multiple high-risk DLBCL and AML patients.…”

“…3 Circulating antibodies to this putative transcription factor were present in multiple high-risk DLBCL and AML patients. 2,3 The PASD1 gene maps to chromosome Xq28, a locus containing many CTA genes, 1 and encodes two PASD1 transcripts, PASD1_v1 and PASD1_v2. In normal tissues, PASD1 mRNA was restricted to testis but its expression in DLBCL cell lines and solid tumors 2 identified PASD1 as a candidate DLBCL-associated CTA.…”

“…Neither antibody labeled the SUDHL-6 or SUDHL-10 (germinal center DLBCL-derived) cells suggesting PASD1 protein expression represents a potential DLBCL subtyping marker. 2 Cytoplasmic Figure 1 The detection of PASD1 protein expression in normal and malignant tissues. (a) Diagram of the PASD_v1 and PASD_v2 proteins illustrating the regions used to produce recombinant GST proteins for monoclonal antibody production (red arrows).…”

PASD1 (PAS domain containing 1)

“…PASD1_v2 lacks intron 14 and a retained stop signal (Liggins et al, 2004a). Differential splicing is predicted to create additional novel PASD1 isoforms as a protein smaller than PASD1_v1 and PASD1_v2 has been detected in OCiLy3 and FEPD cells .…”