Class-I MHC expression in the mouse lung carcinoma, line 1: a model for class-I inducible tumors

The importance of the age factor in cancer vaccination at older age

Cancer is an age-related disease, and with the graying of the society there is an increasing need to optimize cancer management and therapy to elderly patients. Vaccine therapy for cancer is less toxic than chemotherapy or radiation and could be, therefore, especially effective in older, more frail cancer patients. However, it has been shown that older individuals do not respond to vaccine therapy as well as younger adults. This has been attributed to T cell unresponsiveness, a phenomenon also observed in cancer patients per se. Therefore, research is needed to establish whether age-specific tumor-immunological variables permit optimal use of cancer vaccines and therapy in the elderly. This review summarizes the current knowledge of T cell unresponsiveness in cancer patients and elderly, and the results of cancer vaccination in preclinical models at young and old age. Finally, new directions that may lead to effective cancer vaccination at older age will be proposed.

Cancer vaccination: manipulation of immune responses at old age

The incidence of cancer has increased over the last decade, mainly due to an increase in the elderly population. Vaccine therapy for cancer is less toxic than chemotherapy or radiation and could be, therefore, especially effective in older, more frail cancer patients. However, it has been shown that older individuals do not respond to vaccine therapy as well as younger adults. This has been attributed to T-cell unresponsiveness, a phenomenon also observed in cancer patients per se. This review summarizes the current knowledge of impaired T-cell responses in cancer patients and the elderly, and the results of cancer vaccination in preclinical models at young and old age. Finally, various approaches how to manipulate immune responses against cancer by vaccination at older age will be proposed.

Cancer vaccines in old age

The incidence of cancer has increased over the last decade, mainly due to an increase in the elderly population. Vaccine therapy for cancer is less toxic than chemotherapy or radiation and could be, therefore, especially effective in older, more frail cancer patients. However, it has been shown that older individuals do not respond to vaccine therapy as well as younger adults. This has been attributed to T cell unresponsiveness, a phenomenon also observed in cancer patients per se. This review summarizes the current knowledge of T cell unresponsiveness in cancer patients and elderly, the results of cancer vaccination in preclinical models and in clinical trials, and recent data of cancer vaccination at young and old age in preclinical models. Finally, experimental approaches will be proposed how to make cancer vaccines more effective at older age.

Decline in MHC class I expression with increasing thickness of cutaneous melanomas in standard-strain transgenic mouse models

Major histocompatibility complex (MHC) class I proteins are required for the formation of complexes with antigenic peptides that enable cytotoxic T lymphocytes (CTLs) to recognize and lyse target cells. The frequent loss of MHC class I expression reported in human melanomas and melanoma cell lines may therefore be an obstacle to CTL-based immunotherapy. We have investigated the expression of MHC class I proteins in the cutaneous melanomas of Tyr-SV40E (C57BL/6 strain) transgenic mice in order to evaluate their potential as experimental models for immunotherapy. The SV40 large T (LT) oncoprotein, which is expressed exclusively in the melanocytic lineages of these mice, was used as a marker for flow cytometric analysis of the parenchymal (potential target) cells of 35 freshly dissociated samples from 28 primary tumours. All the tumours were ulcerated and exceeded the Breslow thickness indicative of a poor clinical prognosis in human melanoma. Using antibodies against H-2D(b) and H-2K(b) class I proteins, the LT antigen-positive cells were found to have high levels of both these MHC class I molecules in the thinnest tumours (2 mm), whereas the levels tended to decline with increasing tumour thickness. Among the tumours > 4 mm thick, five had no detectable MHC class I expression. Unexpectedly, the apparent loss of H-2D(b) and H-2K(b) proteins was observed not only in LT-positive cells but also in LT-negative cell populations. Expression of both H-2D(b) and H-2K(b) was restored in tumours derived from a class I-low melanoma cell line by treatment of the hosts with interferon-gamma. These results implicate a regulatory defect as a principal cause of the loss of MHC class I antigens, as noted by others in some human tumours, and they demonstrate that this loss is remediable, even in advanced stages of melanomas.

Tailoring cancer vaccines to the elderly: the importance of suitable mouse models

The incidence of cancer has increased over the last decade, mainly due to an increase in the elderly population. Vaccine therapy for cancer is potentially less toxic than chemotherapy or radiation and could, therefore, be especially effective in older, more frail cancer patients. However, it has been shown that older individuals do not respond to vaccine therapy as well as younger adults. This has been attributed to T cell unresponsiveness, a phenomenon also observed in cancer patients per se. Activation of tumor-specific T cells by cancer vaccines might be an approach, especially suitable for elderly patients, to eradicate or to prevent recurrence of tumors after primary treatment. To tailor pre-clinical testing of vaccine therapies to the elderly, it is important to have mouse models in which tumors develop at equivalent time points in their life span, as in humans. Such models are currently not available. This progress report first summarizes the current knowledge of tumor-immunological parameters potentially involved in T cell unresponsiveness in relation to aging in mice and humans. Secondly, it reviews those cancer vaccines that are known for their potential to induce tumor-specific T cell responses. Thirdly, it discusses the usefulness of currently available mouse models for pre-clinical testing of cancer vaccines applicable to the elderly population. Finally, experimental approaches are proposed, as to how to develop mouse models that allow the induction of specific tumors at will at different ages, expressing tumor-specific antigens in an 'immune competent' environment. These mouse models may teach us how to overcome immune deficits in the elderly, thereby facilitating the development of effective and safe cancer vaccines.

Activation of the HIV type 1 long terminal repeat and viral replication by dimethylsulfoxide and related solvents

The HIV-1 long terminal repeat (LTR) introduced into the macrophage cell line THP-1 and the T lymphocyte cell line Jurkat in association with the luciferase reporter gene is activated by the polar, aprotic solvents dimethylsulfoxide (DMSO), dimethylacetamide (DMAC), and dimethylformamide (DMF). These solvents also greatly potentiated the activation of the LTR in THP-1 cells by phorbol myristate acetate (PMA), tumor necrosis factor alpha (TNF-alpha), H202, and a Staphylococcus epidermidis product. Lipopolysaccharide (LPS) and lipoteichoic acid (LTA) at 1 microg/ml had no effect on the LTR in THP-1 cells unless the solvents were added. The aprotic solvents also greatly potentiated the activation of the LTR in Jurkat cells by PMA, TNF-alpha, and H202, whereas LPS, LTA, or the S. epidermidis product had no effect in the presence or absence of the solvents. DMSO, DMAC, and DMF also increased the production of intact virions by latently HIV-1-infected ACH-2, J1.1, U1, and OM10.1 cells under some experimental conditions. The use of the polar aprotic solvents DMSO, DMAC, and DMF, by amplification, may allow the better detection of a weak activator of the LTR and facilitate studies of the mechanism of activation.

Synergistic effects of co-expression of the TH1 cytokines IL-2 and IFN-gamma on generation of murine tumor-reactive cytotoxic cells

While the effect of cytokines on the generation of tumor-reactive cytotoxic cells has been a topic of active investigation, the effect of physiological cytokine combinations has not been determined. We have investigated the effect of co-expression of IL-2 and IFN-gamma on the generation of cytotoxic cells against the murine line 1 tumor in vivo. These cytokines were selected because they are normally produced in concert by a subset of T-helper cells called T-helper 1 (Th1). We transfected the line 1 murine carcinoma with cDNA for IL-2 and IFN-gamma, alone or combined. IFN-gamma alone does not elicit rejection of the transfectant, but IL-2 increases the tumorigenic dose by 10,000-fold above the parental cells. Co-expression of IFN-gamma and IL-2 increases this rejection to at least 100,000-fold above parental line 1. Unlike IL-2 transfectants, tumor cells expressing both IFN-gamma and IL-2 can also elicit rejection of admixed parental tumor cells. Finally, the IFN-gamma/IL-2 transfectants are more effective at generating memory cells that are cytolytic for the parental tumor. Our results show that synergistic interactions of Th1 cytokines can remarkably enhance the cytotoxic response to tumors.

Expression of major histocompatibility class I and class II antigens and intercellular adhesion molecule-1 on operable non-small cell lung carcinomas: frequency and prognostic significance

Major histocompatibility complex (MHC) antigens and adhesion molecules, such as the intercellular adhesion molecule-1 (ICAM-1), appear to play an important role in the immunological recognition and destruction of tumour cells. We, therefore, examined the expression patterns of these proteins on primary tumours of 91 patients with operable non-small cell lung cancer (NSCLC). Applying immunohistochemistry with monoclonal antibody (MAb) W6/32 against a common framework determinant of HLA class I antigens revealed a deficient expression in 33.0% of the cases analysed, while neo-expression of either HLA class II antigens (MAb TAL.1B5) or ICAM-1 (MAb PA3.58-14) was observed in 26.4 or 29.7% of tumours, respectively. Analysis of consecutive tumour specimens indicated that HLA antigens and ICAM-1 were frequently coexpressed. With regard to clinicopathological risk factors, we could demonstrate a preferential expression of those markers in patients with locally restricted and well-differentiated tumours or no lymph node metastases, which was more pronounced in adenocarcinomas than in squamous cell carcinomas. In contrast, the presence versus the absence of HLA antigens and ICAM-1 was not correlated with the rate of tumour recurrence or overall survival in patients with NSCLC. In conclusion, the co-ordinated expression of immunologically relevant cell surface molecules on primary NSCLC is a frequent event that correlates with distinct parameters of favourable prognosis. However, we have no evidence that the immune response facilitated by these molecules can effectively influence the clinical course of the disease.

Assembly of MHC class I molecules in ex vivo carcinoma cells induced by IFN-gamma or by a binding peptide

It has been reported that the assembly of MHC class I molecules in mutagenized cell lines could be induced by specific binding peptides. We have now demonstrated that the defect in assembly between heavy and light chains of class I molecules naturally occurred in tumor cells of one spontaneous ovarian carcinoma detected by one-dimensional isoelectric focusing of immunoprecipitates with anti-monomorphic class I MAb (W6/32) and by immunostaining with free heavy chain and beta 2m-specific MAbs. In vitro treatment of the tumor cells with IFN-gamma induced the assembly and surface expression of majority class I molecules (A2.1, B7, B15, Cw6, Cw7 out of A2.1, A2*, B7, B15, Cw6, Cw7). Moreover, assembly of A2 and Cw6 was induced by exposure of the tumor cells to a HLA A2-binding peptide K62 derived from influenza A matrix protein. Autologous blood T lymphocytes were activated in mixed lymphocyte-tumor cell culture (MLTC) by the IFN-gamma-treated but not by the unmanipulated tumor cells. Although activated lymphocytes damaged both IFN-gamma-treated and untreated tumor cells, the alpha class I MAb (W6/32) efficiently inhibited the lysis of IFN-gamma-treated targets, but not the untreated targets. These results indicate that the defect of MHC class I assembly may result in the escape of tumor cells from immune response.