Prostate-specific membrane antigen

Anti-prostate specific membrane antigen designer T cells for prostate cancer therapy

BACKGROUND

Designer T cells are T lymphocytes engineered toward specific antibody-type membrane antigens through chimeric immunoglobulin-T-cell receptor (IgTCR) genes that have been used for adoptive cellular immunotherapy. We have extended this approach to prostate specific membrane antigen (PSMA) as a means to attack prostate cancer.

METHODS

A chimeric anti-PSMA IgTCR gene was constructed based on an anti-PSMA monoclonal antibody, 3D8. Both T-cell lines and primary cultured human T lymphocytes were transduced with the chimeric anti-PSMA IgTCR construct and were analyzed for IgTCR expression, specific activation by PSMA, cytotoxicity against PSMA-expressing tumor cells in vitro, and retardation of tumor growth in an animal model.

RESULTS

The IgTCR was incorporated into the TCR-CD3 complex and formed a functional chimeric complex. The IgTCR-modified T cells were specifically activated through the chimeric receptor with PSMA as measured by IL-2 production and increased CD25 expression and specifically lysed the PSMA-expressing prostate cancer cells in vitro as well as retarded tumor growth in an animal model.

CONCLUSIONS

The anti-PSMA designer T cells exhibit an antibody-type specificity that can recognize PSMA expressing tumor cells in a MHC-independent fashion, resulting in T-cell activation, target cell lysis in vitro and inhibition of tumor growth in vivo.

Dipeptidyl peptidase IV activity and/or structure homologues (DASH) and their substrates in cancer

Post-translational modification of proteins is an important regulatory event. Numerous biologically active peptides that play an essential role in cancerogenesis contain an evolutionary conserved proline residue as a proteolytic-processing regulatory element. Proline-specific proteases could therefore be viewed as important "check-points". Limited proteolysis of such peptides may lead to quantitative but, importantly, due to the change of receptor preference, also qualitative changes of their signaling potential. Dipeptidyl peptidase-IV (DPP-IV, EC 3.4.14.5, identical with CD26) was for many years believed to be a unique cell membrane protease cleaving X-Pro dipeptides from the N-terminal end of peptides and proteins. Subsequently, a number of other molecules were discovered, exhibiting various degree of structural homology and DPP-IV-like enzyme activity, capable of cleaving similar set of substrates. These comprise for example, seprase, fibroblast activation protein alpha, DPP6, DPP8, DPP9, attractin, N-acetylated-alpha-linked-acidic dipeptidases I, II and L, quiescent cell proline dipeptidase, thymus-specific serine protease and DPP IV-beta. It is tempting to speculate their potential participation on DPP-IV biological function(s). Disrupted expression and enzymatic activity of "DPP-IV activity and/or structure homologues" (DASH) might corrupt the message carried by their substrates, promoting abnormal cell behavior. Consequently, modulation of particular enzyme activity using e.g. DASH inhibitors, specific antibodies or DASH expression modification may be an attractive therapeutic concept in cancer treatment. This review summarizes recent information on the interactions between DASH members and their substrates with respect to their possible role in cancer biology.

Inhibition of prostate-specific membrane antigen (PSMA)-positive tumor growth by vaccination with either full-length or the C-terminal end of PSMA

For experimental immunotherapy of prostate cancer, we used a model system to target a defined region of the extracellular domain of prostate-specific membrane antigen (PSMA). PSMA is a surface antigen expressed by prostate epithelium that is upregulated approximately 10-fold in most prostate tumors. We vaccinated BALB/c mice with NIH3T3 cells cotransfected with pST/neo plus pEF-BOS-based vectors expressing either the full-length 750-amino acid human PSMA or only the C-terminal 180-amino acid region (PSMc). PSMc lies C-terminal to the transferrin receptor-like sequence in the extracellular domain of PSMA. BALB/c mice were injected i.p. 4 times at weekly intervals with vaccine cells. Vaccinated mice were then challenged s.c. with Renca/PSMA, a BALB/c renal cell carcinoma line transfected to express human PSMA. Growth of Renca/PSMA tumors was substantially retarded and host survival significantly prolonged in mice prevaccinated with either 3T3/PSMA or 3T3/PSMc. Furthermore, antiserum from vaccinated mice intensely immunocytochemically stained LNCaP, a PSMA-positive human prostate cancer cell line. In contrast, control mice similarly prevaccinated i.p. with 3T3/neo (NIH3T3 cells transfected with pST/neo alone) developed Renca/PSMA tumors, which were palpable within 2 weeks and lethal by 5 weeks. Serum from 3T3/neo-vaccinated mice did not immunocytochemically stain LNCaP cells. The antitumor activity induced by vaccination with 3T3/PSMc was also demonstrated via growth inhibition of established LNCaP tumors xenografted in athymic mice following passive transfer of immune serum from vaccinated mice. Our results suggest that vaccination with PSMc induces adaptive humoral activity, which is directed against the extracellular region of human PSMA and can significantly inhibit human prostate cancer growth in athymic mice, and that administration of antibodies to PSMA may provide a passive treatment modality for immunocompromised patients.

Prostate-specific membrane antigen (PSMA): current benefits and future value

We will review the evolution, benefits, and limitations of PSMA testing in the past, as well as its current and future value. Prostate cancer has been the most frequently diagnosed cancer and the second leading cause of cancer death in men in the United States. It has a wide spectrum of biological behavior between latent (indolent) and progressive (aggressive). Further identification of prostate-specific membrane antigen (PSMA) as a prognostic proliferation marker may enhance our understanding of the types of prostate cancer. A review of PSMA testing in the past as well as currently was conducted. Studies were reviewed that deal with detection of PSMA in serum and seminal fluid, reverse transcriptase-polymerase chain reaction (RT-PCR), immunoscintigraphy, and immunohistochemical assays. PSMA is expressed primarily in benign and cancerous prostatic epithelial cells. It is up-regulated in hormone resistant states, and in metastatic situations or other clinical situations where there is tumor recurrence or extension. Based on current results, PSMA detected in the serum by western blotting can assist in the identification, staging, and monitoring of metastatic prostate cancer. In addition, PSMA shows a promising role in directed imaging and therapy of recurrent or metastatic disease.

Cytotoxicity of combined essential fatty acids on a human prostate cancer cell line

In this study the effect of single and concomitantly added n-6 or n-3 polyunsaturated fatty acids (PUFAs) was investigated on human prostate cells. Data obtained from the single fatty acids (FAs) experiments showed that except for oleic acid (OA), arachidonic (AA) and linoleic acid (LA), which had very little (less than 10% cells dead) effect on the cells, an increase in dead cells was observed at physiological concentrations of, eicosapentaenoic acid (EPA), gamma-linolenic acid (GLA) and alpha-linolenic acid (ALA). However, this was not the case when combining these acids at physiological concentrations. A slight increase in cell death was only obtained with three combinations of ALA, namely with AA, OA, or GLA. Other combinations with ALA, such as with LA or EPA, had respectively no effect on cell number or increased the cell number by causing less cells to die. Other PUFAs combinations tested, did not show the three groups mentioned with ALA, but only the last two types, namely, no effect, or a decrease in the amount of cell death. The latter might mean that the FA combination had stimulated the cells, since a decrease in the amount of dead cells was observed. Therefore, it is concluded that the characteristics of combined FAs may differ from single FAs, which may explain some controversies in the literature and in response to treatments.