The host-tumor immune conflict: from immunosuppression to resistance and destruction

Downregulation of Interleukin-12 (IL-12) Responsiveness in Human T Cells by Transforming Growth Factor-β: Relationship With IL-12 Signaling

Interleukin-12 (IL-12) is a cytokine that plays a central role in the control of cell-mediated immunity. We have previously shown that transforming growth factor-β1 (TGF-β) inhibitory effects on human primary allogeneic cytotoxicity and proliferative responses interfere with IL-12 pathway. The present study was undertaken to further elucidate the biochemical basis of the functional interaction between these two cytokines and to define the site of TGF-β action on the signaling pathway activated by IL-12. Our data indicate that TGF-β induced an inhibition of interferon-γ (IFN-γ) production without affecting the IL-12Rβ1 and IL-12Rβ2 subunits mRNA expression by activated T cells. We further show that TGF-β has a significant inhibitory effect on the early signal transduction events following interaction of IL-12 with its receptor on activated T cells, resulting in the inhibition of both JAK2 and Tyk2 phosphorylation. In addition, TGF-β was found to significantly inhibit IL-12–induced phosphorylation of the STAT4 transcription factor. Electrophoretic mobility shift assay indicated that TGF-β induced a decrease in IL-12–induced STAT4 DNA binding activity in T lymphocytes. This study suggests that TGF-β influences IL-12 responsiveness at least in part by inhibiting early signaling events essential to gene induction in IL-12–activated T cells.

Expression of CD3-zeta on T-cells in primary cervical carcinoma and in metastasis-positive and -negative pelvic lymph nodes

Lymphocytic infiltrate is often present in cervical cancer lesions, possibly reflecting an ongoing, but ineffective, immune response to the tumour. Recently, evidence has accumulated for systemically impaired T-cell functions in cancer patients, associated with decreased expression of signal-transducing zeta (zeta) chain dimer molecules on circulating T-cells and NK-cells. Here, we report on the intralesional down-regulation of zeta chain expression on T-cells in cervical carcinoma. Paraffin-embedded or snap-frozen sections from 24 different cervical cancer specimens were studied. Paraffin-embedded tumour-positive (n = 7) and tumour-negative (n = 15) pelvic lymph nodes were also included in the study. Immunostaining was performed on consecutive sections with antibodies specific for CD3-epsilon or the CD3-associated zeta chain dimer. Antigen retrieval by sodium citrate/microwave treatment was essential for zeta staining of paraffin sections. The amount of zeta positive cells was quantitated and related to the number of CD3-epsilon+ cells in corresponding tumour areas. Of the 24 cervical cancer specimens studied, zeta chain dimer expression was reduced in seven cases and strongly reduced in the other 17 samples. In tonsil control sections, CD3-epsilon and CD3-zeta were always co-expressed in almost equal numbers. Also, both tumour-negative and -positive lymph nodes showed zeta chain expression which equalled that of CD3-epsilon expression. These data indicate that a decreased expression of signal-transducing zeta molecules on tumour-infiltrating T-cells is frequent in cervical cancer. The apparently unimpaired zeta chain expression within draining lymph nodes suggests that local tumour-derived factors at the primary site are instrumental in zeta chain down-regulation.

Downregulation of Interleukin-12 (IL-12) Responsiveness in Human T Cells by Transforming Growth Factor-β: Relationship With IL-12 Signaling

Interleukin-12 (IL-12) is a cytokine that plays a central role in the control of cell-mediated immunity. We have previously shown that transforming growth factor-β1 (TGF-β) inhibitory effects on human primary allogeneic cytotoxicity and proliferative responses interfere with IL-12 pathway. The present study was undertaken to further elucidate the biochemical basis of the functional interaction between these two cytokines and to define the site of TGF-β action on the signaling pathway activated by IL-12. Our data indicate that TGF-β induced an inhibition of interferon-γ (IFN-γ) production without affecting the IL-12Rβ1 and IL-12Rβ2 subunits mRNA expression by activated T cells. We further show that TGF-β has a significant inhibitory effect on the early signal transduction events following interaction of IL-12 with its receptor on activated T cells, resulting in the inhibition of both JAK2 and Tyk2 phosphorylation. In addition, TGF-β was found to significantly inhibit IL-12–induced phosphorylation of the STAT4 transcription factor. Electrophoretic mobility shift assay indicated that TGF-β induced a decrease in IL-12–induced STAT4 DNA binding activity in T lymphocytes. This study suggests that TGF-β influences IL-12 responsiveness at least in part by inhibiting early signaling events essential to gene induction in IL-12–activated T cells.

Is primary chemotherapy useful for all patients with primary invasive breast cancer?

Chemotherapy dose intensification in breast tumours is being evaluated in many multicentre trials, its indication being based on a clinical response in high-risk patients, thus selecting for tumours with rapid proliferation and low resistance. However, results from randomized trials are still pending. Clinical and pathological responses to therapy are valuable surrogate endpoints following primary chemotherapy. They will make it possible to distinguish at an early stage between patients who still retain an apoptotic response to chemotherapy and those patients whose disease will progress rapidly due to resistance mechanisms. For practical purposes, patients at risk and capable of responding represent the population of choice for primary systemic chemotherapy. Thus, by investigating mechanisms of response and resistance during the first courses of treatment we may target chemotherapy at those patients likely to benefit most from this treatment. A number of immunotherapy and vaccination trials are being conducted in many different centres. There is a lot of anecdotal evidence that cancer vaccines could help patients, but little yet in the way of solid, reproducible clinical data. Best responses to clinical testing would ideally be expected in early-stage disease because there is less tumour bulk and the patient's immune system is still able to respond. Patients with early breast cancer who are at high risk of recurrence and who have failed to respond to primary chemotherapy might be given the option of participating in adjuvant vaccination trials following the completion of local therapy.

The role of macrophages in antitumor defense of patients with ovarian cancer

Macrophages have diverse effects on tumor biology, including neovascularization, growth rate, and stroma formation. Tumor-associated macrophages (TAMs) represent a major subpopulation of the mononuclear leukocytes present in malignant ascites of ovarian cancer patients. TAMs appear to participate in the immunologic antitumor defense mechanism through cytotoxic activities, such as direct cellular cytotoxicity and the release of cytokines, and may represent key targets for a variety of therapeutic interventions.

Inhibition of the Differentiation of Dendritic Cells From CD34+ Progenitors by Tumor Cells: Role of Interleukin-6 and Macrophage Colony-Stimulating Factor

The escape of malignant cells from the immune response against the tumor may result from a defective differentiation or function of professional antigen-presenting cells (APC), ie, dendritic cells (DC). To test this hypothesis, the effect of human renal cell carcinoma cell lines (RCC) on the development of DC from CD34+progenitors was investigated in vitro. RCC cell lines were found to release soluble factors that inhibit the differentiation of CD34+ cells into DC and trigger their commitment towards monocytic cells (CD14+CD64+CD1a−CD86−CD80−HLA-DRlow) with a potent phagocytic capacity but lacking APC function. RCC CM were found to act on the two distinct subpopulations emerging in the culture at day 6 ([CD14+CD1a−] and [CD14−CD1a+]) by inhibiting the differentiation into DC of [CD14+CD1a−] precursors and blocking the acquisition of APC function of the [CD14−CD1a+] derived DC. Interleukin-6 (IL-6) and macrophage colony-stimulating factor (M-CSF) were found to be responsible for this phenomenon: antibodies against IL-6 and M-CSF abrogated the inhibitory effects of RCC CM; and recombinant IL-6 and/or M-CSF inhibited the differentiation of DC similarly to RCC CM. The inhibition of DC differentiation by RCC CM was preceeded by an induction of M-CSF receptor (M-CSFR; CD115) and a loss of granulocyte-macrophage colony-stimulating factor receptor  (GM-CSFR; CD116) expression at the surface of CD34+cells, two phenomenon reversed by anti–IL-6/IL-6R and anti–M-CSF antibodies, respectively. Finally, a panel of tumor cell lines producing IL-6 and M-CSF induced similar effects. Taken together, the results suggest that the inhibition of DC development could represent a frequent mechanism by which tumor cells will escape immune recognition.

Inhibition of the Differentiation of Dendritic Cells From CD34+ Progenitors by Tumor Cells: Role of Interleukin-6 and Macrophage Colony-Stimulating Factor

The escape of malignant cells from the immune response against the tumor may result from a defective differentiation or function of professional antigen-presenting cells (APC), ie, dendritic cells (DC). To test this hypothesis, the effect of human renal cell carcinoma cell lines (RCC) on the development of DC from CD34+progenitors was investigated in vitro. RCC cell lines were found to release soluble factors that inhibit the differentiation of CD34+ cells into DC and trigger their commitment towards monocytic cells (CD14+CD64+CD1a−CD86−CD80−HLA-DRlow) with a potent phagocytic capacity but lacking APC function. RCC CM were found to act on the two distinct subpopulations emerging in the culture at day 6 ([CD14+CD1a−] and [CD14−CD1a+]) by inhibiting the differentiation into DC of [CD14+CD1a−] precursors and blocking the acquisition of APC function of the [CD14−CD1a+] derived DC. Interleukin-6 (IL-6) and macrophage colony-stimulating factor (M-CSF) were found to be responsible for this phenomenon: antibodies against IL-6 and M-CSF abrogated the inhibitory effects of RCC CM; and recombinant IL-6 and/or M-CSF inhibited the differentiation of DC similarly to RCC CM. The inhibition of DC differentiation by RCC CM was preceeded by an induction of M-CSF receptor (M-CSFR; CD115) and a loss of granulocyte-macrophage colony-stimulating factor receptor  (GM-CSFR; CD116) expression at the surface of CD34+cells, two phenomenon reversed by anti–IL-6/IL-6R and anti–M-CSF antibodies, respectively. Finally, a panel of tumor cell lines producing IL-6 and M-CSF induced similar effects. Taken together, the results suggest that the inhibition of DC development could represent a frequent mechanism by which tumor cells will escape immune recognition.

Increased IL-12 P40 homodimer secretion by spleen cells during in vivo growth of the BW-19 T cell hybridoma accompanies suppression of natural immunity

The high capacity of the T cell hybridoma BW-19 to metastasize to the spleen, despite its high and moderate sensitivity to lysis by macrophages and natural killer (NK) cells, respectively, appears to be linked to its capacity to suppress local resident NK cell and macrophage activity. Such suppression of splenic NK cell and macrophage activity is accompanied by an increased production of the p40 subunit of interleukin-12 (IL-12) by spleen cells. Closer examination revealed that most of the p40 subunit is present under the form of the homodimer (p40)2, whereas the heterodimeric form of IL-12 is present only in small amounts. Since (p40)2 is known to be a strong antagonist of IL-12-mediated effects, i.e., NK cell activation and interferon-gamma (IFN-gamma) secretion, the increased production of (p40)2 after BW-19 cell inoculation may contribute to the suppression of NK cell and macrophage activity. In addition, we found that the high production of (p40)2 in our tumor model was accompanied by a drastic decrease in IL-2 and IFN-gamma production by spleen cells, further favoring the possibility that (p40)2 plays a role in the suppression of NK cell and macrophage cytotoxicity. Our results show that normal spleen cells can produce (p40)2 in response to cancer cell growth in vivo and are highly suggestive of a role for (p40)2 in the suppression of natural immunity.

Quantitative analysis of Th1, Th2 and TGF-beta1 cytokine expression in tumor, TIL and PBL of non-small cell lung cancer patients

For understanding the local immune response in human non-small cell lung cancer (NSCLC), we investigated both Th1 and Th2-type as well as TGF-beta1 cytokine mRNA expression in 10 fresh tumor biopsies, the corresponding tumor and short term TIL cell lines as well as patient PBMC. A methodology based on a highly sensitive quantitative RT-PCR was used. We found that IL-6 mRNA was highly expressed in all tumor biopsy samples analyzed (4 LLC, 3 ADC and 3 SCC). IL-10 mRNA was expressed in 7 of 10 biopsies whereas IL-4 mRNA expression was moderate. Analysis of type I cytokines revealed a low expression level of IL-2 mRNA, while IFNgamma and GM-CSF expression was high in the majority of the tumor lesions studied. Quantitatively, high amounts of Th2-type cytokine mRNA were detected at the tumor site with IL-6 as the predominant lymphokine. A high mRNA expression level of the immunosuppressive cytokine TGF-beta1 was observed in all NSCLC. To identify the cell types responsible for the production of TGF-beta1, IL-6, IL-10 and GM-CSF at the tumor site, tumor and TIL cell lines were derived from the corresponding biopsies. All the 3 tumor cell lines analysed were found to express high amount of TGF-beta1 but not IL-10 mRNA, 2 expressing IL-6 and GM-CSF. Five short term TIL cell lines established in the presence of IL-2 expressed high level of IL-10, IL-4 and IFNgamma but not IL-2 mRNA. Strikingly, high expression of IL-10 mRNA was also observed in all 6 patient PBMC analyzed as compared to controls. Together, our results indicate the existence of a local and peripheral Th-2-type cytokine pattern in patients bearing NSCLC.

Gene therapy for lung cancer

Gene therapy has received considerable attention and some speculation as to its value. Although few patients have been treated, the preliminary results of the phase I lung cancer gene therapy clinical trials are very promising. Clinically relevant basic research in the molecular pathogenesis and immunology of lung cancer is progressing. As improved vector technologies are developed, new opportunities will be available to initiate lung cancer gene therapy trials that are based on a more detailed understanding of lung cancer biology. In conclusion, although important biologic and technical questions remain unanswered, recent research suggests that gene therapy will have a profound impact on lung cancer treatment.

Immunogenicity and cross-reactivity with idiotypic IgA of VH CDR3 peptide in multiple myeloma

Multiple myeloma idiotypic protein is clone-specific and therefore represents an ideal tumour antigen for immune targeting. In this study we determined whether a synthetic peptide corresponding to the autologous idiotypic VH CDR3 sequence could elicit peptide-specific immune responses in a patient with IgA myeloma. Not unlike B-cell lymphoma, the immune repertoire of the patient contained T cells capable of mounting proliferative and cytotoxic responses to antigen-presenting cells loaded with the CDR3 peptide. Furthermore, the T cells were also able to secrete interferon-gamma upon peptide rechallenge. Antigen recognition by peptide-primed T cells was MHC dependent and could be blocked by antibodies to both monomorphic MHC class I and class II molecules. These results therefore indicate the presence of T-cell epitopes on the VH CDR3 sequence. In addition, CDR3 peptide-primed T cells were also able to mount similar immune responses when rechallenged with the intact IgA idiotypic protein, suggesting that functional T-cell epitopes had been derived from the CDR3 sequence of the idiotypic protein. Our results therefore provide a new perspective to the immunogenicity of the idiotypic protein in myeloma.