Cellules dendritiques et gliomes : un espoir en immunothérapie ?

Immunotherapy has been explored for several decades to try to improve the prognosis of gliomas, but until recently no therapeutic benefit has been achieved. The discovery of dendritic cells, the most potent professional antigen presenting cells to initiate specific immune response, and the possibility of producing them ex vivo gave rise to new protocols of active immunotherapy. In oncology, promising experimental and clinical therapeutic results were obtained using these dendritic cells loaded with tumor antigen. Patients bearing gliomas have deficit antigen presentation making this approach rational. In several experimental glioma models, independent research teams have showed specific antitumor responses using these dendritic cells. Phase I/II clinical trials have demonstrated the feasibility and the tolerance of this immunotherapeutic approach. In neuro-oncology, the efficiency of such an approach remains to be established, similarly in oncology where positive phase III studies are missing. Nevertheless, dendritic cells comprise a complex network which is only partially understood and capable of generating either immunotolerance or immune response. Numerous parameters remain to be explored before any definitive conclusion about their utility as an anticancer weapon can be drawn. It seems however logical that immunotherapy with dendritic cells could prevent or delay tumor recurrence in patients with minor active disease. A review on glioma and dendritic cells is presented.

TRF2 inhibition promotes anchorage-independent growth of telomerase-positive human fibroblasts

Although telomere instability is observed in human tumors and is associated with the development of cancers in mice, it has yet to be established that it can contribute to the malignant transformation of human cells. We show here that in checkpoint-compromised telomerase-positive human fibroblasts an episode of TRF2 inhibition promotes heritable changes that increase the ability to grow in soft agar, but not tumor growth in nude mice. This transforming activity is associated to a burst of telomere instability but is independent of an altered control of telomere length. Moreover, it cannot be recapitulated by an increase in chromosome breaks induced by an exposure to gamma-radiations. Since it can be revealed in the context of telomerase-proficient human cells, telomere dysfunction might contribute to cancer progression even at late stages of the oncogenesis process, after the telomerase reactivation step.

Dendritic cells are essential for priming but inefficient for boosting antitumour immune response in an orthotopic murine glioma model

The prognosis of malignant gliomas remains dismal and alternative therapeutic strategies are required. Immunotherapy with dendritic cells (DCs) pulsed with tumour antigens emerges as a promising approach. Many parameters influence the efficacy of DC-based vaccines and need to be optimised in preclinical models. The present study compares different vaccine schedules using DCs loaded with tumour cell lysate (DC-Lysate) for increasing long-term survival in the GL26 orthotopic murine glioma model, focusing on the number of injections and an optimal way to recall antitumour immune response. Double vaccination with DC-Lysate strongly prolonged median survival compared to unvaccinated animals (mean survival 87.5 days vs. 25 days; p < 0.0001). In vitro data showed specific cytotoxic activity against GL26. However, late tumour relapses frequently occurred after 3 months and only 20% of mice were finally cured at 7 months. While one, two or three DC injections gave identical survival, a boost using only tumour lysate after initial DC-Lysate priming dramatically improved long-term survival in vaccinated mice, compared to the double DC-Lysate group, with 67.5% of animals cured at 7 months (p < 0.0001). In vitro data showed better specific CTL response and also the induction of specific anti-GL26 antibodies in the DC-Lysate/Lysate group, which mediated Complement Dependent Cytotoxicity. These experimental data may be of importance for the design of clinical trials that currently use multiple DC injections.

Canarypox virus expressing wild type p53 for gene therapy in murine tumors mutated in p53

The antitumor activity of a recombinant canarypox virus expressing wild type murine p53 (ALVAC-p53) was investigated in two murine syngeneic tumors harboring an endogenous p53 mutation (CMS4 and TS/A). Direct intratumor injections of ALVAC-p53 in CMS4 pre-established subcutaneous tumors induced total tumor regression in 66% of mice. Furthermore, 100% of the cured mice was protected against a contralateral subsequent challenge with the parental tumor cells. The intravenous treatment of experimental lung metastasis by ALVAC-p53 also induced significant tumor growth inhibition in both models. The antitumor effect of ALVAC-p53 was only observed in immunocompetent animals and was associated with the generation of a specific antitumor immune response. ALVAC-p53 induced the expression of a functional p53 wild type protein as demonstrated by up-regulation of p21waf1 and induction of apoptosis. A vaccine strategy using intravenous or subcutaneous ALVAC-p53/NYVAC-p53 prime boost protocol failed to induce CTL against p53 wild type used as target tumor antigen, and failed to protect mice against challenge with the mutated tumor cells. The mechanism of the curative and protective effects observed after direct intratumor injections results from the induction of a specific antitumor response directed against other antigens than p53. Our results suggest that the local induction of tumor apoptosis, combined with the adjuvant effect of ALVAC vector, enhances the immunogenicity of the intratumor environment and allows induction of specific antitumor immune response.

T-cell repertoire analysis in chronic plaque psoriasis suggests an antigen-specific immune response

Psoriasis is a chronic inflammatory cutaneous disease of unknown etiology. Activation of T cells is thought to play a major role in the pathophysiology of psoriasis. In order to gain insight into the nature of the antigen (superantigen or nominal protein antigen) involved in psoriatic lesions, we have used a RT-PCR method to analyze the frequency of the 24 T cell receptor V beta chain (TCRBV) subfamilies and the size of the antigen-binding region (CDR3), using the immunoscope assay, in skin lesions of patients with chronic plaque-type psoriasis. Semi-quantitative analysis showed that no significant difference in V beta subfamily usage could be detected in T lymphocytes infiltrating lesional skin as compared to blood lymphocytes. Alternatively, determination of the size distribution of the CDR3 of all the V beta subfamilies revealed only in psoriatic skin a marked TCR oligoclonality defined by the presence in 3 to 5 V beta subfamilies of a single predominant CDR3 size which was associated with a unique V beta-J beta combination. Identical patterns of CDR3 length and V beta-J beta combination profiles were found in symetrical lesional sites from two psoriatic patients. This type of skewed CDR3 size profile is reminiscent of a local stimulation of T lymphocytes by nominal protein antigens. These data suggest that T lymphocytes infiltrating plaque-type psoriatic skin comprise expansions of oligoclonal T cells in response to stimulation by an antigen present in the skin.

Canarypox virus-mediated interleukin 12 gene transfer into murine mammary adenocarcinoma induces tumor suppression and long-term antitumoral immunity

The antitumoral activity of recombinant canarypox virus vectors (ALVAC) expressing murine interleukin 12 (IL-12) was evaluated in the syngeneic, nonimmunogenic murine mammary adenocarcinoma model (TS/A). Seven-day preestablished subcutaneous tumors (5- to 6-mm mean diameters) were injected on days 7, 10, 14, 17, 21, and 24 with the vector ALVAC-IL12 at 2.5 x 10(5) TCID50 (50% tissue culture infective dose). Total tumor regression occurred in 40 to 50% of the treated mice. Furthermore, 100% of the cured mice were protected against a contralateral subsequent challenge with the TS/A parental cells on day 28. The ALVAC-IL12 treatment is not effective in nude mice, suggesting the critical role of T cells. CD4 and CD8 T cells infiltrated the tumors treated with ALVAC-IL12 in the BALB/c model. Furthermore, in vivo depletion of CD4+ T cells totally abrogated the induction of the long-term antitumoral immune response by ALVAC-IL12. Interestingly, some tumor growth inhibition was also observed with ALVAC-betaGal treatment and a vaccinal effect was found in 33% of the treated animals, suggesting an adjuvant effect of the vector itself. Other ALVAC vectors expressing murine cytokines (IL-2, GM-CSF, IFN-gamma) were evaluated in the same model. Major antitumoral activity was observed with ALVAC-GM-CSF. However, a combination of ALVAC-GM-CSF and ALVAC-IL12 had no synergistic effect. These results suggest that in vivo gene transfer with canarypox virus expressing IL-12 may provide an effective and safe strategy for the treatment of human cancers.

Correlation between clinical response to interleukin 2 and HLA phenotypes in patients with metastatic renal cell carcinoma

HLA phenotypes were characterized for 79 patients with metastatic renal cell carcinoma treated with interleukin 2 (IL-2). HLA-A32 was associated with a clinical response (P = 0.025). The frequency of HLA-A3 and/or A32 was higher among responders than non-responders (P = 0.008). Thus, these results suggest that, in vivo, IL-2 may enhance cellular-mediated immunity against a tumour antigen and that some MHC molecules are more efficient than others for endogenous tumour antigen presentation.

B7.1 gene transduction of human renal-cell-carcinoma cell lines restores the proliferative response and cytotoxic function of allogeneic T cells

Renal-cell-carcinoma is one of the human tumors for which the immune response may control the growth of tumor cells. Conversely, T cells infiltrating this tumor have been reported to be impaired in proliferative and effector functions. Complete activation of T cells requires 2 signaling events, one through the antigen-specific receptor and one through the B7 ligand, CD28. In the present study, we first showed the absence of B7.1 expression on RCC tumors and cell lines, and the low proliferative response of allogeneic T cells upon stimulation with these cells. Transduction of the human gene for B7.1 rendered these cells potent stimulators of allogeneic mixed lymphocyte response. Furthermore, stimulation of purified CD4+ and CD8+ T-cell populations showed that transduced cell lines preferentially induced the proliferation of CD8+ T cells. Finally, mixed lymphocyte cultures in the presence of the B7.1+ cell lines led to the generation of cytotoxic T lymphocytes able to specifically recognize both the transduced stimulator and the parental cell line. We thus demonstrate that B7.1 expression on human tumor cell lines is capable of inducing MHC-class-I-dependent proliferation and differentiation into cytotoxic effectors of allogeneic CD8+ T cells. The lack of B7 expression on RCC cell lines is responsible for their failure to activate allogeneic T cells, a result which strongly suggests that the same mechanism may be implied in the impaired tumor-cell presentation to autologus T cells.

Restriction of the T-cell repertoire in tumor-infiltrating lymphocytes from nine patients with renal-cell carcinoma. Relevance of the CDR3 length analysis for the identification of in situ clonal T-cell expansions

Renal-cell carcinoma (RCC) is one of the human cancers which respond best to immunotherapy. To better characterize the mechanism of the immune response in RCC, we analyzed the T-cell receptor (TCR) beta-chain repertoire in primary RCC, metastases and paired peripheral blood lymphocytes (PBL) from 9 patients. For 3 of these, we analyzed T cells recovered from normal kidney, or from tumor-involved lymph nodes as well as tumor-infiltrating lymphocytes (TIL) expanded in vitro for adoptive immunotherapy. The initial semi-quantitative RT-PCR method for definition of the Vbeta gene usage was not informative enough to distinguish intratumoral clonal T-cell expansions. In contrast, the length pattern analysis of the complementary determining regions 3 (CDR3) allowed oligoclonal T-cell populations to be detected in fresh TIL form the 9 patients with RCC. Furthermore, these oligoclonal TIL populations were not present in normal renal tissue, autologous PBL or tumor-involved lymph nodes. Different clonal T-cell expansions were identified in the primary tumor and in a pulmonary metastasis from the same patient. The detection of clonal T-cell populations observed in RCC suggests an in situ expansion in response to potential tumor antigens. This report provides an overall and accurate description of the T-cell repertoire in a significant number of samples from patients with RCC.

T-cell repertoires in healthy and diseased human tissues analysed by T-cell receptor beta-chain CDR3 size determination: evidence for oligoclonal expansions in tumours and inflammatory diseases

Many examples of oligoclonal T-cell expansion in infiltrated diseased tissues have been reported. However, it remains to be established whether such observations can be generalized and to what extent oligoclonal patterns obtained after in vitro culture of T-cell infiltrates reflect in vivo situations. Using new high resolution analysis which requires no in vitro cellular expansion, we detected such oligoclonal T-cell expansions in 7/7 melanoma tumour biopsies, 3/3 biopsies of inflammatory skin during acute graft versus host disease (aGVHD) after allogeneic bone marrow transplantation (alloBMT) and 7/7 synovial membranes from patients with rheumatoid arthritis. Thus, oligoclonal T-cell expansions are readily observed when a sufficiently sensitive detection method is used, suggesting that similar expansions are the rule among T-cell infiltrates in different diseases. This observation and the monitoring of the in vivo evolution of such expansion during the course of the disease and during in vitro culture should have important clinical implications.

Oligoclonality of tumor-infiltrating lymphocytes from human melanomas

A PCR-based method that determines VDJ junction size patterns in 24 human TCR V beta subfamilies was used to analyze T cells infiltrating sequential malignant melanoma biopsies for the presence of clonal expansions. Infiltrating T cell populations were found to present clonal expansions over a more or less complex polyclonal background. Two clones from a single patient were sequenced and detected in three different tumor sites (skin biopsies), whereas only one of them was also present in peripheral blood. Biopsies from this patient did not show major repertoire changes during in vivo IL-2 treatment. In contrast, in biopsies from a second patient, the expression of all the detected V beta subfamilies was increased and a larger number of clones expanded, probably as a result of therapy. A similar evolution was found among infiltrating T cells cultured in vitro from a third patient for several weeks in the presence of IL-2, where the largely polyclonal repertoire of fresh T cells (from invaded lymph nodes) was dramatically reduced to mainly clonal expansions in all V beta subfamilies detected. The high resolution method used here enables a rapid, comprehensive, qualitative, and semiquantitative description of the T cell repertoire of heterogeneous cell populations. Its use in conjunction with a functional analysis of clones detected within these populations should provide a better understanding of the evolution of the T cell repertoire among tumor-infiltrating lymphocytes during the progression of the disease and as a response to immunotherapy.

Oligoclonality of tumor-infiltrating lymphocytes from human melanomas

A PCR-based method that determines VDJ junction size patterns in 24 human TCR V beta subfamilies was used to analyze T cells infiltrating sequential malignant melanoma biopsies for the presence of clonal expansions. Infiltrating T cell populations were found to present clonal expansions over a more or less complex polyclonal background. Two clones from a single patient were sequenced and detected in three different tumor sites (skin biopsies), whereas only one of them was also present in peripheral blood. Biopsies from this patient did not show major repertoire changes during in vivo IL-2 treatment. In contrast, in biopsies from a second patient, the expression of all the detected V beta subfamilies was increased and a larger number of clones expanded, probably as a result of therapy. A similar evolution was found among infiltrating T cells cultured in vitro from a third patient for several weeks in the presence of IL-2, where the largely polyclonal repertoire of fresh T cells (from invaded lymph nodes) was dramatically reduced to mainly clonal expansions in all V beta subfamilies detected. The high resolution method used here enables a rapid, comprehensive, qualitative, and semiquantitative description of the T cell repertoire of heterogeneous cell populations. Its use in conjunction with a functional analysis of clones detected within these populations should provide a better understanding of the evolution of the T cell repertoire among tumor-infiltrating lymphocytes during the progression of the disease and as a response to immunotherapy.

Inhibition of human colon cancer growth by antibody-directed human LAK cells in SCID mice

Advanced human colon cancer does not respond to lymphokine-activated killer (LAK) cells. In order to direct cytotoxic cells to the tumor, human LAK cells linked with antibodies to a tumor cell surface antigen were tested with established hepatic metastases in severe combined immunodeficient (SCID) mice. These cells had increased uptake into the tumor and suppression of tumor growth as compared with LAK cells alone, thereby improving the survival of tumor-bearing mice. Thus, tumor growth can be inhibited by targeted LAK cells, and SCID mice can be used to test the antitumor properties of human effector cells.