Restoration of the expression of transporters associated with antigen processing in lung carcinoma increases tumor-specific immune responses and survival

A wide variety of human carcinomas have low expression of tumor-associated antigen presentation in the context of MHC class I antigens due to defects in the antigen presentation pathway. This immune evasion mechanism renders many tumors unrecognizable by host immune surveillance mechanisms. The present study examines the expression of HLA, tapasin, transporter associated with antigen processing 1 (TAP1), and beta2 microglobulin in human small cell lung carcinoma and non-small cell lung carcinoma. Immunohistochemical staining showed severe impairment of the antigen presentation pathway in all patients. In order to recover tumor immunogenicity, a nonreplicating adenovirus expressing human TAP1 (AdhTAP1) was used to restore the expression of TAP1 in the antigen presentation pathway-deficient mouse lung carcinoma cell line, CMT.64. Infection of CMT.64 cells with AdhTAP1 increased MHC class I antigen surface expression, antigen presentation, and susceptibility to antigen-specific CTLs. Fluorescence-activated cell sorting and ELISPOT analysis showed that AdhTAP1 treatment significantly increased dendritic cell cross-presentation and cross-priming of tumor antigens. Furthermore, ex vivo and in vivo AdhTAP1 treatment significantly retarded tumor growth and increased survival of mice bearing CMT.64 tumors. Fluorescence-activated cell sorting analysis and immunohistochemical staining showed a significant increase in CD8+ and CD4+ T cells and CD11c+ dendritic cells infiltrating the tumors. The results show that TAP should be considered as a part of the immunotherapies for various cancers because it is likely to provide a general method for increasing immune responses against tumors regardless of the antigenic composition of the tumor or the MHC haplotypes of the host.

Combining the antigen processing components TAP and Tapasin elicits enhanced tumor-free survival

PURPOSE

Tpn is a member of the MHC class I loading complex and functions to bridge the TAP peptide transporter to MHC class I molecules. Metastatic human carcinomas often express low levels of the antigen-processing components Tapasin and TAP and display few functional surface MHC class I molecules. As a result, carcinomas are unrecognizable by effector CTLs. The aim of this study is to examine if Tapasin (Tpn) plays a critical role in the escape of tumors from immunologic recognition.

EXPERIMENTAL DESIGN

To test our hypothesis, a nonreplicating adenovirus vector encoding human Tpn (AdhTpn) was constructed to restore Tpn expression in vitro and in vivo in a murine lung carcinoma cell line (CMT.64) that is characterized by down-regulation of surface MHC class I due to deficiency in antigen-processing components.

RESULTS

Ex vivo, Tpn expression increased surface MHC class I and restored susceptibility of tumor cells to antigen-specific CTL killing, and AdhTpn infection of dendritic cells also significantly increased cross-presentation and cross-priming. Furthermore, tumor-bearing animals inoculated with AdhTpn demonstrated a significant increase in CD8(+) and CD4(+) T cells and CD11c(+) dendritic cells infiltrating the tumors. Provocatively, whereas syngeneic mice bearing tumors that were inoculated with AdhTpn a significant reduction in tumor growth and increased survival compared with vector controls, combining AdhTpn inoculation with AdhTAP1 resulted in a significant augmentation of protection from tumor-induced death than either component alone.

CONCLUSIONS

This is the first demonstration that Tpn alone can enhance survival and immunity against tumors but additionally suggests that Tpn and TAP should be used together as components of immunotherapeutic vaccine protocols to eradicate tumors.

Tumour immunity and T cell memory are induced by low dose inoculation with a non-replicating adenovirus encoding TAP1

Despite continued progress in understanding the pathophysiology of tumours, curative therapeutic options are still lacking for the metastatic form of the disease. One approach that has gathered considerable interest is the creation of therapeutic vaccines using genetically engineered non-replicating viruses as vehicles to revive immunosurveillance mechanisms that may eradicate residual tumour cells. A perceived problem with this approach is that the number of non-replicating viruses used as a vaccine inoculum does not remotely approximate the total number of cells in the body, nor even the number of tumour cells in the case of large tumour burden or metastasis. Here, we addressed the hypothesis that a limited amount of inoculum (1x10(8) PFU) of recombinant non-replicating adenovirus encoding human TAP1 (AdhTAP1) can induce protective immunity against 1.5x10(5) TAP-deficient, metastatic melanoma cells transplanted into a normal mouse (total of approximately 1x10(11) body cells). We show that efficacious anti-tumour cytolytic T cell responses are indeed induced by injecting melanoma-bearing animals with small numbers of recombinant viruses, resulting in increases in tumour-infiltrating dendritic cells, enhanced memory T cell subpopulations and, most importantly, in increased animal survival. This novel approach uses a limited input inoculum relative to the tumour cell mass, and thus achieves an efficacious outcome that has so far eluded other vaccine, immunotherapeutic or gene therapeutic strategies where there is a requisite for the majority of tumour cells to be transduced for beneficial outcome to be achieved.