Enhanced growth of primary tumors in cancer-prone mice after immunization against the mutant region of an inherited oncoprotein.

One major objective of tumor immunologists is to prevent cancer development in individuals at high risk. (TG.AC x C57BL/6)F1 mice serve as a model for testing the feasibility of this objective. The mice carry in the germline a mutant ras oncogene that has an arginine at codon 12 instead of glycine present in the wild-type, and after physical (wounding) or chemical promotion, these mice have a high probability for developing papillomas that progress to cancer. Furthermore, F1 mice immunized with Arg(12) mutant ras peptide in complete Freund's adjuvant (CFA) develop T cells within 10 d that proliferate in vitro on stimulation with the Arg(12) mutant ras peptide. Within 14 d, these mice have delayed-type hypersensitivity to the peptide. Immunization with CFA alone or with a different Arg(12) mutant ras peptide in CFA induced neither response. To determine the effect of immunization on development of tumors, mice immunized 3 wk earlier were painted on the back with phorbol 12-myristate 13-acetate every 3 d for 8 wk. The time of appearance and the number of papillomas were about the same in immunized and control mice, but the tumors grew faster and became much larger in the mice immunized with the Arg(12) mutant ras peptide. Thus, the immunization failed to protect against growth of papillomas. The peptide-induced CD4(+) T cells preferentially recognized the peptide but not the native mutant ras protein. On the other hand, mice immunized with Arg(12) mutant ras peptide and bearing papillomas had serum antibodies that did bind native mutant ras protein. Together, these studies indicate that active immunization of cancer-prone individuals may result in immune responses that fail to eradicate mutant oncogene-expressing tumor cells, but rather induce a remarkable enhancement of tumor growth.

The relationship of untreated borderline infiltrates by the Banff criteria to acute rejection in renal allograft biopsies.

The relationship of borderline infiltrates to acute rejection by Banff criteria in renal allografts of patients receiving only maintenance immunosuppression is not clear. Renal allograft biopsies with borderline lesions that were not treated with additional anti-rejection therapy were retrospectively studied. Sixty-five such biopsies were identified from 50 patients, and their outcome was determined by serum creatinine and/or histologic findings in subsequent biopsies, up to 40 d after the initial biopsy. In addition to the borderline infiltrates, there was evidence of acute cyclosporine or tacrolimus toxicity (58%), acute tubular necrosis (12%), and urinary obstruction (12%). Forty-day follow-up after 30 (46%) biopsies revealed serum creatinine < 110% of baseline, and repeat biopsies were not indicated. In 17 (26%), the serum creatinine initially decreased, then increased, and follow-up biopsies showed acute rejection in nine. In 18 (28%), the creatinine remained elevated and follow-up biopsies revealed acute rejection in nine. The untreated borderline infiltrates were thus nonprogressive after 47 biopsies (72%) and progressed to histologic acute rejection after 18 (28%). When there was increasing or persistently elevated creatinine after the initial biopsy, 51% of cases (18 of 35) progressed to acute rejection. Infiltrates that progressed to rejection had more frequent glomerulitis (7 of 18 versus 3 of 47, P = 0.003) and Banff acute score indices (i+t+v+g) >2 (16 of 18 versus 29 of 47, P = 0.03). A majority (72%) of borderline infiltrates not given additional anti-rejection therapy did not progress to acute rejection over 40 d of follow-up, suggesting that conservative management of these lesions, at least in the short term, may be more appropriate than routine treatment as acute rejection.

Complications in 100 living-liver donors.

OBJECTIVE: A review of 100 living-liver donors was performed to evaluate the perisurgical complications of the procedure and thus to help quantify the risks to the donor. SUMMARY BACKGROUND DATA: Despite the advantages of living-donor liver transplantation (LDLT), the procedure has received criticism for the risk it imposes on healthy persons. A paucity of data exists regarding the complications and relative safety of the procedure. METHODS: One hundred LDLTs performed between November 1989 and November 1996 were reviewed. Donor data were obtained by chart review, anesthesia records, and the computerized hospital data base. Patient variables were compared by Fisher's exact test and the Student's t test. RESULTS: There were 57 women and 43 men with a median age of 29. Donors were divided into two groups: group A (first 50 donors), and group B (last 50 donors). There were 91 left lateral segments and 9 left lobes. There were no deaths. Fourteen major complications occurred in 13 patients; 9 occurred in group A and 5 in group B. Biliary complications consisted of five bile duct injuries (group A = 4, group B = 1) and two cut edge bile leaks. Complications were more common in left lobe resections (55%) than in left lateral segment grafts (10%). Minor complications occurred in 20% of patients. A significant reduction in overall complications (major and minor) was observed between the groups (group A, n = 24 [45%] vs. group B, n = 10 [20%]). In addition, surgical time and hospital stay were both significantly reduced. CONCLUSIONS: Although the procedure is safe, many LDLT donors have a perisurgical complication. Surgical experience and technical modifications have resulted in a significant reduction in these complications, however. To minimize the risks for these healthy donors, LDLT should be performed at institutions with extensive experience.

Tumor cells induce cytolytic T cells to a single immunodominant mutant peptide.

Two different approaches have shown that cancers express mutant proteins that may be recognized as tumor-specific antigens. On the one hand, DNA sequences known to be mutant in tumor cells have been used to select for mutant peptides that induce tumor-specific T cells (the so-called "reverse immunologic" approach). On the other, T cells induced by vaccination with whole tumor cells have been used to identify tumor-specific mutations in proteins ("direct immunologic approach"). While both approaches generate tumor-specific T cells that can lyse cancer cells expressing the relevant mutant protein, the present study suggests that there may be crucial differences. Mutant epitopes originally defined from DNA sequences have so far been immunorecessive, and tumor cells themselves generally appear unable to induce specific CD8+ T cells that recognize the encoded mutant gene product. In contrast, we find that mutant epitopes identified by CD8+ T cells stimulated by immunization with whole tumor cells induce cytolytic T cells to such mutant peptides. In fact, much or all of the response appears to be to a single mutant octapeptide that seems to be immunodominant. One possible reason for the failure of immunorecessive antigens to induce a response may be the presence of lower amounts of the antigen in the cancer cell, but other mechanisms are possible as well. For example, in the host bearing a growing tumor, neither purified proteins nor peptides might be known; thus, only immunodominant unique antigens may be able to restimulate and activate tumor-specific memory T cells that localize in the tumor following active immunization.

Antigenic cancer cells grow progressively in immune hosts without evidence for T cell exhaustion or systemic anergy.

One enigma in tumor immunology is why animals bearing malignant grafts can reject normal grafts that express the same nonself-antigen. An explanation for this phenomenon could be that different T cell clones react to the normal graft and the malignant cells, respectively, and only the tumor-reactive clonotypes may be affected by the growing tumor. To test this hypothesis, we used a T cell receptor transgenic mouse in which essentially all CD8(+) T cells are specific for a closely related set of self-peptides presented on the MHC class I molecule Ld. We find that the tumor expressed Ld in the T cell receptor transgenic mice but grew, while the Ld-positive skin was rejected. Thus, despite an abundance of antigen-specific T cells, the malignant tissue grew while normal tissue expressing the same epitopes was rejected. Therefore, systemic T cell exhaustion or anergy was not responsible for the growth of the antigenic cancer cells. Expression of costimulatory molecules on the tumor cells after transfection and preimmunization by full-thickness skin grafts was required for rejection of a subsequent tumor challenge, but there was no detectable effect of active immunization once the tumor was established. Thus, the failure of established tumors to attract and activate tumor-specific T cells at the tumor site may be a major obstacle for preventive or therapeutic vaccination against antigenic cancer.

The immunodominant antigen of an ultraviolet-induced regressor tumor is generated by a somatic point mutation in the DEAD box helicase p68.

The genetic origins of CD8+ T cell-recognized unique antigens to which mice respond when immunized with syngeneic tumor cells are unknown. The ultraviolet light-induced murine tumor 8101 expresses an H-2Kb-restricted immunodominant antigen, A, that induces cytolytic CD8+ T cells in vivo A+ 8101 cells are rejected by naive mice while A- 8101 tumor cells grow. To identify the antigen H-2Kb molecules were immunoprecipitated from A+ 8101 cells and peptides were eluted by acid. The sensitizing peptide was isolated by sequential reverse-phase HPLC and sequenced using microcapillary HPLC-triple quadruple mass spectrometry. The peptide, SNFVFAGI, matched the sequence of the DEAD box protein p68 RNA helicase except for a single amino acid substitution, caused by a single nucleotide change. This mutation was somatic since fibroblasts from the mouse of tumor origin expressed the wild-type sequence. The amino acid substitution created an anchor for binding of the mutant peptide to H-2Kb. Our results are consistent with mutant p68 being responsible for rejection of the tumor. Several functions of p68, which include nucleolar assembly and inhibition of DNA unwinding, may be mediated through its IQ domain, which was altered by the mutation. This is the first description of a somatic tumor-specific mutation in the coding region of a nucleic acid helicase.

A unique tumor antigen produced by a single amino acid substitution.

Mice immunized against a cancer recognize antigens unique to that cancer, but the molecular structures of such antigens are unknown. We isolated CD4+ T cell clones recognizing an antigen uniquely expressed on the UV-induced tumor 6132A; some clones inhibited the growth of tumors bearing the specific antigen. A T cell hybridoma was used to purify this antigen from nuclear extracts by RP-HPLC and SDS-PAGE using T cell immunoblot assays. A partial amino acid sequence was nearly identical to a sequence in ribosomal protein L9. The cDNA sequence of L9 from 6132A PRO cells differed from the normal sequence at one nucleotide; this mutation encoded histidine instead of leucine at position 47. A synthetic peptide containing this mutation was over 1000-fold more stimulatory of T cells than was the wild-type peptide. These results indicate that this unique tumor antigen is derived from a single amino acid substitution in a cellular protein.