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Tim F Greten

Publications and source records attributed to Tim F Greten.

12 recordsLinked to original sources
PubMed2026

Plasma cell-CD8+ T cell co-enrichment distinguishes immunotherapy-responsive hepatocellular carcinoma subtypes.

BACKGROUND: Hepatocellular carcinoma (HCC) is characterised by significant racial disparities in incidence and outcomes, yet whether these reflect distinct tumour biology or differential distribution of molecular subtypes among immunotherapy patients remains unclear. METHODS: We characterised molecular heterogeneity among 46 patients with HCC of differing background population from the NCI-CLARITY cohort receiving immune checkpoint inhibitor therapy, using transcriptomic and genomic profiling, with validation across multiple independent cohorts. RESULTS: Differential expression analysis comparing African American versus non-African American patients identified 126 genes, of which 55 demonstrated tumour-specific expression across independent validation cohorts with paired tumour-normal samples. Consensus clustering revealed two molecular subtypes with no significant race association, indicating these clusters capture tumour-intrinsic biology rather than ancestry. The genomic landscape showed minimal differences between subtypes. A prognostic signature derived from these expression profiles demonstrated significant risk stratification in the NCI-CLARITY cohort and TCGA-LIHC, but not in Asian cohorts, suggesting population-specific applicability. Immune deconvolution revealed that the two subtypes represent distinct immune microenvironments: one subtype exhibited markedly elevated plasma cell infiltration with strong plasma cell-CD8+T cell correlation suggesting coordinated adaptive immunity, along with elevated tertiary lymphoid structure signatures. The other subtype showed regulatory T cell-macrophage correlation and enrichment for immune-excluded phenotypes. The immune-enriched subtype trended towards higher immunotherapy response rates. CONCLUSIONS: Molecular heterogeneity in HCC reveals distinct tumour-immune ecosystems that transcend racial classification. Tumour immune heterogeneity in HCC reflects distinct molecular patterns, with immune hot tumours characterised by elevated tertiary lymphoid structure signatures and enriched plasma cell and CD8+T cells. These patterns may serve as prognostic biomarkers for immunotherapy patient stratification and demonstrate the value of diverse cohort representation in identifying clinically relevant therapeutic targets.

Gastrointestinal Cancer↗
PubMed2006

Genetically induced pancreatic adenocarcinoma is highly immunogenic and causes spontaneous tumor-specific immune responses.

Treatment options for pancreatic cancer are limited and often ineffective. Immunotherapeutic approaches are one possible option that needs to be evaluated in appropriate animal models. The aim of the present study was to analyze tumor-specific immune responses in a mouse model of pancreatic cancer, which mimics the human disease closely. C57BL/6 EL-TGF-alpha x Trp53-/- mice, which develop spontaneous ductal pancreatic carcinoma, were generated. EL-TGF-alpha x Trp53-/- mice developed spontaneous pancreatic tumors with pathomorphologic features close to the human disease. Tumor-specific CD8+ T-cell responses and IgG responses were analyzed in EL-TGF-alpha x Trp53-/- mice during tumor development and compared with mice with s.c. growing pancreatic tumors. In contrast to spontaneous pancreatic tumors, cell lines generated from these tumors were rejected after s.c. injection into wild-type mice but not in nude or RAG knockout mice. Direct comparison of spontaneous and s.c. injected tumors revealed an impaired infiltration of CD8+ T cells in spontaneous pancreatic tumors, which was also evident after adoptive transfer of tumor-specific T cells. Intratumoral cytokine secretion of tumor necrosis factor-alpha, IFN-gamma, IL-6, and MCP-1 was lower in spontaneous tumors as well as the number of adoptively transferred tumor-specific T cells. Our data provide clear evidence for tumor-specific immune responses in a genetic mouse model for pancreatic carcinoma. Comparative analysis of s.c. injected tumors and spontaneous tumors showed significant differences in tumor-specific immune responses, which will help in improving current immune-based cancer therapies against adenocarcinoma of the pancreas.

Animals↗
PubMed2005

Increased populations of regulatory T cells in peripheral blood of patients with hepatocellular carcinoma.

Hepatocellular carcinoma (HCC) is the fifth most common cancer worldwide with a poor prognosis and one for which immunotherapy remains a viable option. Experimental tumor models have shown that regulatory T cells, a functionally unique subset of T cells, can suppress effective antitumor immune responses. This suppression might explain the poor outcome of some of the immunotherapy protocols currently being used. A better understanding of the role of regulatory T cells in HCC is important for design of future immunotherapy-based clinical protocols. We have studied regulatory T cells from 84 patients with HCC and 74 controls, including healthy donors, patients with chronic hepatitis B virus and hepatitis C virus infection and nonviral liver cirrhosis. Regulatory T cells were identified by fluorescence-activated cell sorting using a panel of antibodies and by real-time PCR analysis for Foxp3 expression. Functional studies were done to analyze their inhibitory role. Finally, regulatory T cells were analyzed in tumors and ascites from patients with HCC. Patients with HCC have increased numbers of CD4+CD25+ regulatory T cells in their peripheral blood, which express high levels of HLA-DR, GITR, and low or no CD45RA. These cells were anergic toward T-cell receptor stimulation and, when cocultured with activated CD4+CD25- cells, potently suppressed their proliferation and cytokine secretion. There were also high numbers of regulatory T cells in tumor-infiltrating lymphocytes of HCC patients comparable with the increase in their peripheral blood. Our data suggest that the increase in frequency of regulatory T cells might play a role in modulation of the immune response against HCC and could be important in design of immunotherapeutic approaches.

Adult↗
PubMed2004

IKKbeta links inflammation and tumorigenesis in a mouse model of colitis-associated cancer.

A link between inflammation and cancer has long been suspected, but its molecular nature remained ill defined. A key player in inflammation is transcription factor NF-kappaB whose activity is triggered in response to infectious agents and proinflammatory cytokines via the IkappaB kinase (IKK) complex. Using a colitis-associated cancer model, we show that although deletion of IKKbeta in intestinal epithelial cells does not decrease inflammation, it leads to a dramatic decrease in tumor incidence without affecting tumor size. This is linked to increased epithelial apoptosis during tumor promotion. Deleting IKKbeta in myeloid cells, however, results in a significant decrease in tumor size. This deletion diminishes expression of proinflammatory cytokines that may serve as tumor growth factors, without affecting apoptosis. Thus, specific inactivation of the IKK/NF-kappaB pathway in two different cell types can attenuate formation of inflammation-associated tumors. In addition to suppressing apoptosis in advanced tumors, IKKbeta may link inflammation to cancer.

Animals↗
PubMed2004

Spontaneous tumor-specific humoral and cellular immune responses to NY-ESO-1 in hepatocellular carcinoma.

PURPOSE: Hepatocellular carcinoma (HCC) is the fifth most common cancer around the world. Although several therapeutic approaches for treatment of HCC are available, survival rates for HCC patients are still very poor because of inefficient treatment options. For HCC, as well as other tumors, antigen-specific immunotherapy remains a viable approach that is dependent on the definition of tumor-associated antigens. NY-ESO-1, a member of the cancer testis antigen family, is one possible candidate for a tumor-specific antigen in HCC. The aim of this study was to show the relevance of NY-ESO-1 in hepatocellular carcinoma. EXPERIMENTAL DESIGN: Sera samples from 189 HCC patients were analyzed for NY-ESO-1-specific antibodies. Forty-nine HCC patients were screened for NY-ESO-1 mRNA expression in HCC tissue. Selected patients were followed for up to 3 years to correlate their immune response with their clinical course of events. NY-ESO-1-specific CD4+ and CD8+ T-cell responses from NY-ESO-1 seropositive patients were analyzed and a NY-ESO-1+ specific cytotoxic T-cell line was generated. RESULTS: Twelve of 49 analyzed tumor samples expressed NY-ESO-1 mRNA and 23 of 189 patients showed NY-ESO-1-specific antibody responses. These humoral immune responses were accompanied by NY-ESO-1-specific functional CD4+ and CD8+ T-cell responses. Finally, NY-ESO-1 humoral responses were dependent on the presence of NY-ESO-1-expressing tumors. CONCLUSIONS: This is the first report of a spontaneous immune response in HCC patients to a known tumor-specific antigen, NY-ESO-1 protein. Our data favor the possibility of immunotherapeutic strategies for the treatment of HCC.

Adult↗
PubMed2004

Maintenance of peritoneal B-1a lymphocytes in the absence of the spleen.

Positive selection by autoantigens is believed to play an important role in the generation/maintenance of B-1a cells. Recently, it has been described that splenectomy results in the loss of an already established B-1a cell pool. To elucidate whether the spleen influences the peritoneal B-1a repertoire, we have analyzed the consequences of splenectomy in the recently established IgL-transgenic L2 mouse model. L2 mice are characterized by a severe block of B-2 development and predominance of B-1a cells, which exhibit a pronounced IgH oligoclonality, presumably due to positive selection by autoantigens. In this study, we show that, in striking contrast to splenectomized normal mice, L2 mice exhibit unchanged frequencies of peritoneal B-1a cells. The IgH repertoire of these B-1a cells, however, was severely perturbed in that the previously described predominant B-1a H chains were no longer present. The repertoire changes were partial since phosphatidylcholine-specific B-1a cells were present in similar numbers before and after splenectomy. Thus, splenic Ags appear to act as "survival factors" for major subsets of peritoneal B cells. The loss of B-1a cells in the absence of such factors is compensated by repertoire changes among B-1a cells in B cell lymphopenic L2 but not normal mice.

Amino Acid Sequence↗
PubMed2003

Apoptotic, but not necrotic, tumor cell vaccines induce a potent immune response in vivo.

Prophylactic tumor vaccination against subsequent tumor challenge depends on effective cross-priming in vivo. Professional APCs process tumor antigens from whole tumor cells and present them to CD4(+) and CD8(+) T cells. Data suggest that dendritic cells process antigens more efficiently from necrotic cells than from apoptotic cells in vitro. We compared the effect of apoptosis vs. necrosis in vivo using different tumor models (CT26, RENCA, B16 and CT26-HA). Apoptosis was induced by gamma-irradiation prior to injection and verified in vivo. Apoptotic CT26-HA, CT26-wt or RENCA prevented tumor outgrowth in 100%, 75% and 100%, respectively, of mice for more than 30 days after challenge. In contrast, injection of necrotic tumor cells led to protection of no more than 0-30%. Prolonged tumor-free survival was also observed in mice after vaccination with irradiated B16 cells. In vivo protection experiments correlated very well with in vitro cytotoxicity assays. Immunohistochemical analysis of the vaccine site showed a strong CD4(+) and CD8(+) T-cell response after injection of apoptotic cells, which was accompanied by the presence of dendritic cells. In contrast, necrotic cell vaccines attracted a strong local macrophage response. Our data clearly demonstrate that only apoptotic tumor cell vaccines induce a potent antitumor immune response.

Animals↗
PubMed2003

CD40 in hepatocellular carcinoma: relevant or not?

The expression of the CD40 receptor in different tumours suggests that it might be involved in tumour development and proliferation. In this article, we discuss recent findings on CD40 expression in hepatocellular carcinoma, its possible biological role for tumour development, and different experimental therapeutic strategies such as gene therapy and immunotherapy protocols.

Animals↗
PubMed2002

Peptide-beta2-microglobulin-MHC fusion molecules bind antigen-specific T cells and can be used for multivalent MHC-Ig complexes.

Recombinant soluble MHC molecules are widely used for visualization, activation and inhibition of antigen-specific immune responses. Using a genetic approach, we have generated two novel peptide-beta2-microglobulin-MHC constructs. We have linked the MHC molecule with the peptide of interest, without limiting the recognition by the cognate TCR. This molecule can also be joined with the IgG heavy chain resulting in a dimeric MHC-Ig fusion protein. These molecules bind antigen-specific T cells with high specificity and sensitivity, therefore, providing a valuable tool for detection as well as enrichment of antigen-specific T cells.

Animals↗
PubMed2002

Stat3 and NF-kappaB activation prevents apoptosis in pancreatic carcinogenesis.

BACKGROUND & AIMS: Human pancreatic adenocarcinoma has an overall poor prognosis. Therapeutic efforts are often ineffective because of late diagnosis and a high degree of chemoresistance. Overexpression of transforming growth factor alpha in the pancreas of transgenic mice causes the formation of premalignant ductal lesions and the development of invasive ductal adenocarcinoma. The aim of the present study was to explore regulation of proapoptotic and antiapoptotic signals during pancreatic tumor development in mice. METHODS: EL-TGFalpha-hGH transgenic mice crossbred to p53-deficient mice develop ductal pancreatic adenocarcinoma resembling the human disease. During the multistep carcinogenesis up-regulation of Bcl-x(L) is evident early and persists throughout tumorigenesis as detected by Real Time PCR, Western blot analysis, and immunofluorescence. RESULTS: Up-regulation of Bcl-x(L) is evident early in tumor development and persists throughout tumorigenesis. The transcription factors Stat3 and NF-kappaB induce increased Bcl-x(L) expression in the premalignant lesions and tumor cells. Inhibition of either transcription factor alone leads to Bcl-x(L) down-regulation in transient transfection assays. Functional analysis shows that blocking of both Stat3 and NF-kappaB together induces programmed cell death in murine pancreatic tumor cells. CONCLUSIONS: These findings indicate that apoptosis resistance precedes formation of invasive pancreatic cancer. Therefore, combined inhibition of Stat3 and NF-kappaB might represent a novel strategy for tumor prevention and therapy.

Animals↗