Molecular characterization of defective antigen processing in human prostate cancer

Martin G. Sanda, Nicholas P. Restifo, Jonathan C. Walsh, Yutaka Kawakami, William G. Nelson, Drew M. Pardoll, Jonathan W. Simons

Research output: Contribution to journalArticlepeer-review

195 Scopus citations


Background:Gene-modified tumor cell vaccines have shown efficacy in animal models of malignancy, including prostate cancer. Class I major histocompatibility complex (MHC) assembly and function in the cellular targets of such therapies is pivotal in determining the efficacy of specific cytokine-secreting tumor vaccines.Purpose To help guide development of genetically engineered vaccine therapy for human prostate cancer, potential immune resistance pathways were evaluated by analysis of class I MHC assembly in prostate cancer cells. Method: Class I MHC assembly in metastasis-derived human prostate cancer cell lines (LNCaP, PPC-1, DU-145, PC-3, and TSU) and a normal prostate-derived cell line (TP-2) were characterized by phenotypic, molecular, and functional assays. Assembled class I MHC and antigen was measured by flow cytometry; mRNA levels of assembly components (class I MHC heavy chain,; β2-microglobulin, and the antigen transporter gene product TAP-2) were determined; and antigen processing was measured with a chimeric reconstituted system using vaccinia vectors. Restoration of antigen processing was attempted by interferon gamma stimulation and by transfection with mouse class I MHC heavy-chain cDNA. Results: Assembled class I MHC was underexpressed in two (LNCaP and PPC-1) of five prostate cancer cell lines compared with normal prostate-derived controls. PPC-1 cells underexpressed TAP-2 mRNA despite abundant class I MHC and β2-microglobulin message. Induction of TAP-2 by interferon gamma indicated that coding sequences for TAP-2 message were present in PPC-1. Resistance to cytotoxic T lymphocytes (CTL) lysis showed a functional defect in antigen transport by PPC-1 cells; reversal of the molecular defect with interferon gamma led to restoration of functional antigen processing. In contrast, LNCaP cells had competent antigen transport but deficient class I MHC heavy-chain function despite abundant class I MHC RNA; though refractory to stimulation by interferon gamma, this defect responded to transfection of class I MHC heavy-chain cDNA. Conclusions: Metastatic prostate cancer cells can escape T-cell recognition via divergent mechanisms of defective class I MHC assembly. The specific under-expression of TAP-2 gene product in PPC-1 cells contrasts with prior studies of TAP gene underexpression in lung cancer (which concurrently underexpressed class I MHC heavy chain) and provides evidence for a regulatory pathway controlling TAP-2 gene expression in human cancers that may not affect class I MHC heavy-chain expression- Implications:In clinical application of gene therapy for prostate cancer, these findings provide a rationale for focusing on strategies that can circumvent sole reliance on class I MHC-mediated tumor cell recognition by CTL. [J Natl Cancer Inst 87: 280-285, 1995]

Original languageEnglish (US)
Pages (from-to)280-285
Number of pages6
JournalJournal of the National Cancer Institute
Issue number4
StatePublished - Feb 15 1995

ASJC Scopus subject areas

  • Oncology
  • Cancer Research


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