Combination immunotherapy induces distinct T-cell repertoire responses when administered to patients with different malignancies

Background

CTLA-4 blockade with ipilimumab is Food and Drug Administration-approved for melanoma as a monotherapy and has been shown to modulate the circulating T-cell repertoire. We have previously reported clinical trials combining CTLA-4 blockade with granulocyte-macrophage colony-stimulating factor (GM-CSF) in metastatic melanoma patients and in metastatic castration resistant prostate cancer (mCRPC) patients. Here, we investigate the effect that cancer type has on circulating T cells in metastatic melanoma and mCRPC patients, treated with ipilimumab and GM-CSF.

Methods

We used next-generation sequencing of T-cell receptors (TCR) to compare the circulating T cells of melanoma and mCRPC patients receiving the same treatment with ipilimumab and GM-CSF by Wilcoxon rank sum test. Flow cytometry was utilized to investigate specific T-cell populations. TCR sequencing results were correlated with each T-cell subpopulation by Spearman’s rank correlation coefficient. Of note, 14 metastatic melanoma patients had samples available for TCR sequencing and 21 had samples available for flow cytometry analysis; 37 mCRPC patients had samples available for sequencing of whom 22 have TCR data available at both timepoints; 20 of these patients had samples available for flow cytometry analysis and 16 had data available at both timepoints.

Results

While melanoma and mCRPC patients had similar pretreatment circulating T-cell counts, treatment induces greater expansion of circulating T cells in melanoma patients. Metastatic melanoma patients have a higher proportion of clones that increased more than fourfold after the treatment compared with mCRPC patients (18.9% vs 11.0%, p=0.017). Additionally, melanoma patients compared with mCRPC patients had a higher ratio of convergent frequency (1.22 vs 0.60, p=0.012). Decreases in clonality induced by treatment are associated with baseline CD8+ T-cell counts in both patient groups, but are more pronounced in the melanoma patients (r=−0.81, p<0.001 vs r=−0.59, p=0.02).

Trial registration numbers

NCT00064129; NCT01363206.

Attenuating CD3 affinity in a PSMAxCD3 bispecific antibody enables killing of prostate tumor cells with reduced cytokine release

BACKGROUND

Therapeutic options currently available for metastatic castration-resistant prostate cancer (mCRPC) do not extend median overall survival >6 months. Therefore, the development of novel and effective therapies for mCRPC represents an urgent medical need. T cell engagers (TCEs) have emerged as a promising approach for the treatment of mCRPC due to their targeted mechanism of action. However, challenges remain in the clinic due to the limited efficacy of TCEs observed thus far in solid tumors as well as the toxicities associated with cytokine release syndrome (CRS) due to the usage of high-affinity anti-CD3 moieties such as OKT3.

METHODS

Using genetically engineered transgenic rats (UniRat and OmniFlic) that express fully human IgG antibodies together with an NGS-based antibody discovery pipeline, we developed TNB-585, an anti-CD3xPSMA TCE for the treatment of mCRPC. TNB-585 pairs a tumor-targeting anti-PSMA arm together with a unique, low-affinity anti-CD3 arm in bispecific format. We tested TNB-585 in T cell-redirected cytotoxicity assays against PSMA+ tumor cells in both two-dimensional (2D) cultures and three-dimensional (3D) spheroids as well as against patient-derived prostate tumor cells. Cytokines were measured in culture supernatants to assess the ability of TNB-585 to induce tumor killing with low cytokine release. TNB-585-mediated T cell activation, proliferation, and cytotoxic granule formation were measured to investigate the mechanism of action. Additionally, TNB-585 efficacy was evaluated in vivo against C4-2 tumor-bearing NCG mice.

RESULTS

In vitro, TNB-585 induced activation and proliferation of human T cells resulting in the killing of PSMA+ prostate tumor cells in both 2D cultures and 3D spheroids with minimal cytokine release and reduced regulatory T cell activation compared with a positive control antibody that contains the same anti-PSMA arm but a higher affinity anti-CD3 arm (comparable with OKT3). In addition, TNB-585 demonstrated potent efficacy against patient-derived prostate tumors ex vivo and induced immune cell infiltration and dose-dependent tumor regression in vivo.

CONCLUSIONS

Our data suggest that TNB-585, with its low-affinity anti-CD3, may be efficacious while inducing a lower incidence and severity of CRS in patients with prostate cancer compared with TCEs that incorporate high-affinity anti-CD3 domains.

Abstract 2981: Clonal deletion of tumor-specific T cells by combination checkpoint blockade compromises antitumor efficacy in low tumor burden states

A myriad of combination immunotherapies is being developed as cancer treatments with the goal of enhancing antitumor immunity. We found that depending on the disease setting, combined immune checkpoint blockade may not always lead to synergistic antitumor effects. While combined anti-CTLA-4 and anti-PD-1 improves control of established tumors, this combination can paradoxically compromise antitumor immunity in the low tumor burden state in preclinical models as well as in melanoma patients. This paradoxical outcome results from treatment-induced apoptosis of tumor-specific T cells. These changes further alter the overall T-cell receptor repertoire. Activated tumor-specific T cells express higher levels of IFN-γ receptor and are more susceptible to apoptosis. Deficiency of IFN-γ receptor on immune cells rescues this phenotype and restores antitumor activity. Additionally, tumor-specific T cells lacking the IFN-γ receptor demonstrate a significant survival advantage compared to their wild-type counterparts in tumor-bearing mice receiving combination therapy. Finally, combination therapy induces significantly higher levels of IFN-γ in the low versus high tumor burden state on a per cell basis, reflecting their less exhausted immune status. Thus, the optimal immunotherapy strategy may depend on disease context, and may not always favor more potent combination immunotherapies.

Citation Format: Chien-Chun Steven Pai, Xiaoqing Lu, Donald Simons, Michel DuPage, Kole T. Roybal, Mingyi Chen, Serena Kwek, Amy-Jo Casbon, Gillian A. Kinsbury, Lawrence Fong. Clonal deletion of tumor-specific T cells by combination checkpoint blockade compromises antitumor efficacy in low tumor burden states [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2981.

Systemic GM-CSF Recruits Effector T Cells into the Tumor Microenvironment in Localized Prostate Cancer

Granulocytic-macrophage colony-stimulating factor (GM-CSF) is used as an adjuvant in cancer vaccine trials and has the potential to enhance antitumor efficacy with immunotherapy; however, its immunologic effects are not fully understood. Here, we report results from a phase I study of neoadjuvant GM-CSF in patients with localized prostate cancer undergoing radical prostatectomy. Patients received subcutaneous injections of GM-CSF (250 μg/m²/day) daily for 2 weeks (cohort 1; n = 6), 3 weeks (cohort 2; n = 6), or 4 weeks (cohort 3; n = 6). Treatment was well tolerated with all grade 1 or 2 adverse events. Two patients had a decline in prostate-specific antigen (PSA) of more than 50%. GM-CSF treatment increased the numbers of circulating mature myeloid dendritic cells, proliferating conventional CD4 T cells, proliferating CD8 T cells, and to a lesser magnitude FoxP3⁺ regulatory CD4 T cells. Although GM-CSF treatment did not augment antigen-presenting cell localization to the prostate, treatment was associated with recruitment of CD8⁺ T cells to the tumor. These results suggest that systemic GM-CSF can modulate T-cell infiltration in the tumor microenvironment. Cancer Immunol Res; 4(11); 948-58. ©2016 AACR.

Abstract 276: Recruitment of effector T cells into the tumor rim and center with neoadjuvant systemic GM-CSF in patients with localized prostate cancer

Background: Granulocyte-macrophage colony-stimulating factor (GM-CSF, sargramostim) is a bone marrow growth factor that is often used as an adjuvant in cancer vaccine clinical trials and has the potential to enhance antitumor efficacy in combination with immune checkpoint blockade in preclinical studies and clinical trials. The effect of GM-CSF remains controversial, however. In this study, we sought to characterize the systemic and tissue-specific effects of GM-CSF in prostate cancer patients in the preoperative setting.

Methods: Patients with localized prostate cancer were treated on an open-label phase I/II study of neoadjuvant GM-CSF prior to planned radical prostatectomy (NCT00305669). Patients received GM-CSF 250mcg/m2 subcutaneously on days 1-14 (cohort 1), days1-21 (cohort 2), or days 1-28 (cohort 3), and underwent radical prostatectomy (RP) within 5 days after the last dose of GM-CSF. Blood collected at baseline, day 14, pre-RP, and 6 weeks post-RP were analyzed for immune cell subsets by flow cytometry. Immune infiltration in RP tissue were evaluated by immunohistochemistry and quantified by digital image analysis with comparison to RP tissue from untreated prostate cancer patients as controls.

Results: 18 patients were evaluated with 6 patients at each dose level. Treatment with GM-CSF was associated with an increase in the number of myeloid cells including myeloid dendritic cells. Treatment was also associated with increases in circulating conventional CD4 and CD8 T cells and NK cells. The number of FoxP3+ regulatory CD4+ T cells was also increased, but to a much lower magnitude. At the time of radical prostatectomy, treatment was associated with a recruitment of CD3+ T cells to the tumor rim, and with cohort 3, at the centers of tumor. These T cells were predominantly CD8+ T cells, although conventional CD4+ T cells were also increased. No increase in monocytes or dendritic cells was seen in the tissue.

Conclusion: Daily injection of systemic GM-CSF induces an increase in circulating antigen presenting cells as well as T and NK cells. While this treatment does not enhance the frequency of antigen presenting cells in the tumor microenvironment, this treatment recruits effector CD8+ T cells into the tumor rims.

Citation Format: Xiao X. Wei, Stephen Chan, Jera Lewis, Serena Kwek, Vinh Dao, Lawrence Fong. Recruitment of effector T cells into the tumor rim and center with neoadjuvant systemic GM-CSF in patients with localized prostate cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 276. doi:10.1158/1538-7445.AM2015-276

An aberrant prostate antigen-specific immune response causes prostatitis in mice and is associated with chronic prostatitis in humans

Chronic prostatitis is a common disease of unclear etiology and has no specific treatment. Mice deficient in the expression of the autoimmune regulator (Aire) gene, which are defective in thymic expression of self antigens and central tolerance, develop spontaneous prostatitis. In this study, we found that Aire-deficient mice developed spontaneous B and T cell immune responses to a prostate autoantigen, seminal vesicle secretory protein 2 (SVS2), which we believe to be novel. We show that thymic expression of this self antigen was Aire dependent. Moreover, prostatitis was induced in WT mice through immunization with SVS2, demonstrating that immunity to SVS2 was sufficient to induce prostatitis. The clinical relevance of this antigen was highlighted by our observation that patients with chronic prostatitis possessed specific autoantibodies against the human SVS2-like seminal vesicle protein semenogelin. These results provide direct evidence that spontaneous chronic prostatitis is an autoimmune disease and is regulated by both central and peripheral tolerance. Moreover, SVS2 and semenogelin are among the relevant autoantigens in mice and humans, respectively.

Abstract 2539: CTLA-4 blockade for hormone refractory prostate cancer: Dose-dependent induction of CD8+ T cell activation and clinical responses

CTLA-4 is a costimulatory molecule expressed on activated T cells that delivers an inhibitory signal to these T cells. CTLA4 blockade with antibody treatment has been shown to augment T cell responses and anti-tumor immunity in animal models and is being developed as an immunotherapy for cancer patients. We performed a phase I trial in patients with metastatic, hormone refractory prostate cancer (HRPC) where sequential cohorts of 3-6 patients were treated with escalating doses (0.5, 1.5 or 3 mg/kg) of ipilimumab, a fully human anti-CTLA-4 antibody (Medarex/BMS), given IV on day 1 of each 28-day cycle x 4 cycles. Patients also received GM-CSF (sargramostim, Berlex) 250 mg/m2/d SC on days 1-14 of the 28-day cycles. Patients were monitored for toxicity as well as for T cell activation. PSA and radiographic tests were performed at baseline and through therapy to evaluate for clinical response. 24 patients have been treated in the initial phase of this study. Of 6 patients treated on the highest dose level (3.0 mg/kg x 4), 3 (50%) had confirmed PSA declines of &gt;50%, and one of these patients had a partial response in hepatic metastases. Immune-related adverse events associated with ipilimumab treatment were also seen more frequently at higher doses of treatment. Expansion of CD25+CD69+ CD8 T cells was also seem primarily at the highest dose level. The treatment also induced an antibody and CD8 T cell immune response to NY-ESO-1. These results demonstrate that CTLA-4 blockade induces not only the expansion of activated effector CD8 T cells in vivo in cancer patients, but also can induce from the endogenous T cell repertoire of these patients T cells that are specific for tumor-associated antigens. CD8 T cell activation, toxicity, and clinical responses also appear to be dose-dependent. Supported by NIH P50 CA89520.

Genome position and gene amplification

Genomic analyses of human cells expressing dihydrofolate reductase provide insight into the effects of genome position on the propensity for a drug-resistance gene to amplify in human cells.

Background

Amplifications, regions of focal high-level copy number change, lead to overexpression of oncogenes or drug resistance genes in tumors. Their presence is often associated with poor prognosis; however, the use of amplification as a mechanism for overexpression of a particular gene in tumors varies. To investigate the influence of genome position on propensity to amplify, we integrated a mutant form of the gene encoding dihydrofolate reductase into different positions in the human genome, challenged cells with methotrexate and then studied the genomic alterations arising in drug resistant cells.

Results

We observed site-specific differences in methotrexate sensitivity, amplicon organization and amplification frequency. One site was uniquely associated with a significantly enhanced propensity to amplify and recurrent amplicon boundaries, possibly implicating a rare folate-sensitive fragile site in initiating amplification. Hierarchical clustering of gene expression patterns and subsequent gene enrichment analysis revealed two clusters differing significantly in expression of MYC target genes independent of integration site.

Conclusion

These studies suggest that genome context together with the particular challenges to genome stability experienced during the progression to cancer contribute to the propensity to amplify a specific oncogene or drug resistance gene, whereas the overall functional response to drug (or other) challenge may be independent of the genomic location of an oncogene.

p53 is involved in tumor necrosis factor-alpha-induced apoptosis in the human prostatic carcinoma cell line LNCaP

The human prostatic carcinoma cell line LNCaP is sensitive to TNF-alpha treatment and expresses wild-type p53. To analyse the possible role of p53 in TNF-alpha-mediated apoptosis, we generated a derivative of LNCaP, LN-56, expressing a dominant-negative element of p53, GSE56. P53 inactivation in LN-56 was associated with an increased resistance to apoptosis induced by TNF-alpha. Surface expression of TNF-alpha receptors was unchanged in LN-56 compared to LNCaP. TNF-alpha treatment resulted in accumulation of p53 in LNCaP and upregulation of p21/WAF1. Activation of caspase-7 and PARP proteolysis were delayed in LN-56 under TNF-alpha treatment. TNF-alpha-induced apoptosis in LNCaP cells was accompanied by caspase-dependent proteolysis of p21/WAF1 and Rb, which was significantly attenuated in LN-56. Cytochrome c release was induced by TNF-alpha treatment in both cell lines, but caspase-9 was not activated. LNCaP and LN-56 were injected s.c. in nude mice and tumors were identified in all LN-56, but not LNCaP, bearing mice indicating that p53 plays an important role in growth control of prostatic neoplasms. Interestingly, accumulation of p53 in TNF-alpha-treated LNCaP cells was decreased in the presence of the caspase inhibitor Z-VAD-FMK, suggesting a new role of activated caspases in acceleration of p53 response. In summary, these results indicate that p53 is involved in TNF-alpha-mediated apoptosis in LNCaP.