Nivolumab with or without ipilimumab in patients with recurrent or metastatic cervical cancer (CheckMate 358): a phase 1-2, open-label, multicohort trial.

BACKGROUND: In preliminary findings from the recurrent or metastatic cervical cancer cohort of CheckMate 358, nivolumab showed durable anti-tumour responses, and the combination of nivolumab plus ipilimumab showed promising clinical activity. Here, we report long-term outcomes from this cohort. METHODS: CheckMate 358 was a phase 1-2, open-label, multicohort trial. The metastatic cervical cancer cohort enrolled patients from 30 hospitals and cancer centres across ten countries. Female patients aged 18 years or older with a histologically confirmed diagnosis of squamous cell carcinoma of the cervix with recurrent or metastatic disease, an Eastern Cooperative Oncology Group performance status of 0 or 1, and up to two previous systemic therapies were enrolled into the nivolumab 240 mg every 2 weeks group, the randomised groups (nivolumab 3 mg/kg every 2 weeks plus ipilimumab 1 mg/kg every 6 weeks [NIVO3 plus IPI1] or nivolumab 1 mg/kg every 3 weeks plus ipilimumab 3 mg/kg every 3 weeks for four cycles then nivolumab 240 mg every 2 weeks [NIVO1 plus IPI3]), or the NIVO1 plus IPI3 expansion group. All doses were given intravenously. Patients were randomly assigned (1:1) to NIVO3 plus IPI1 or NIVO1 plus IPI3 via an interactive voice response system. Treatment continued until disease progression, unacceptable toxicity, or consent withdrawal, or for up to 24 months. The primary endpoint was investigator-assessed objective response rate. Anti-tumour activity and safety were analysed in all treated patients. This study is registered with ClinicalTrials.gov (NCT02488759) and is now completed. FINDINGS: Between October, 2015, and March, 2020, 193 patients were recruited in the recurrent or metastatic cervical cancer cohort of CheckMate 358, of whom 176 were treated. 19 patients received nivolumab monotherapy, 45 received NIVO3 plus IPI1, and 112 received NIVO1 plus IPI3 (45 in the randomised group and 67 in the expansion group). Median follow-up times were 19·9 months (IQR 8·2-44·8) with nivolumab, 12·6 months (7·8-37·1) with NIVO3 plus IPI1, and 16·7 months (7·2-27·5) with pooled NIVO1 plus IPI3. Objective response rates were 26% (95% CI 9-51; five of 19 patients) with nivolumab, 31% (18-47; 14 of 45 patients) with NIVO3 plus IPI1, 40% (26-56; 18 of 45 patients) with randomised NIVO1 plus IPI3, and 38% (29-48; 43 of 112 patients) with pooled NIVO1 plus IPI3. The most common grade 3-4 treatment-related adverse events were diarrhoea, hepatic cytolysis, hyponatraemia, pneumonitis, and syncope (one [5%] patient each; nivolumab group), diarrhoea, increased gamma-glutamyl transferase, increased lipase, and vomiting (two [4%] patients each; NIVO3 plus IPI1 group), and increased lipase (nine [8%] patients) and anaemia (seven [6%] patients; pooled NIVO1 plus IPI3 group). Serious treatment-related adverse events were reported in three (16%) patients in the nivolumab group, 12 (27%) patients in the NIVO3 plus IPI1 group, and 47 (42%) patients in the pooled NIVO1 plus IPI3 group. There was one treatment-related death due to immune-mediated colitis in the NIVO1 plus IPI3 group. INTERPRETATION: Nivolumab monotherapy and nivolumab plus ipilimumab combination therapy showed promise in the CheckMate 358 study as potential treatment options for recurrent or metastatic cervical cancer. Future randomised controlled trials of nivolumab plus ipilimumab or other dual immunotherapy regimens are warranted to confirm treatment benefit in this patient population. FUNDING: Bristol Myers Squibb and Ono Pharmaceutical.

Circulating cancer-specific CD8 T cell frequency is associated with response to PD-1 blockade in Merkel cell carcinoma.

Understanding cancer immunobiology has been hampered by difficulty identifying cancer-specific T cells. Merkel cell polyomavirus (MCPyV) causes most Merkel cell carcinomas (MCCs). All patients with virus-driven MCC express MCPyV oncoproteins, facilitating identification of virus (cancer)-specific T cells. We studied MCPyV-specific T cells from 27 patients with MCC using MCPyV peptide-HLA-I multimers, 26-color flow cytometry, single-cell transcriptomics, and T cell receptor (TCR) sequencing. In a prospective clinical trial, higher circulating MCPyV-specific CD8 T cell frequency before anti-PD-1 treatment was strongly associated with 2-year recurrence-free survival (75% if detectable, 0% if undetectable, p = 0.0018; ClinicalTrial.gov: NCT02488759). Intratumorally, such T cells were typically present, but their frequency did not significantly associate with response. Circulating MCPyV-specific CD8 T cells had increased stem/memory and decreased exhaustion signatures relative to their intratumoral counterparts. These results suggest that cancer-specific CD8 T cells in the blood may play a role in anti-PD-1 responses. Thus, strategies that augment their number or mobilize them into tumors could improve outcomes.

Intratumoral SIRPα-deficient macrophages activate tumor antigen-specific cytotoxic T cells under radiotherapy.

Radiotherapy (RT)-induced tumoricidal immunity is severely limited when tumors are well-established. Here, we report that depleting SIRPα on intratumoral macrophages augments efficacy of RT to eliminate otherwise large, treatment-resistant colorectal (MC38) and pancreatic (Pan02 and KPC) tumors, inducing complete abscopal remission and long-lasting humoral and cellular immunity that prevent recurrence. SIRPα-deficient macrophages activated by irradiated tumor-released DAMPs exhibit robust efficacy and orchestrate an anti-tumor response that controls late-stage tumors. Upon RT-mediated activation, intratumoral SIRPα-deficient macrophages acquire potent proinflammatory features and conduct immunogenic antigen presentation that confer a tumoricidal microenvironment highly infiltrated by tumor-specific cytotoxic T cells, NK cells and inflammatory neutrophils, but with limited immunosuppressive regulatory T cells, myeloid derived suppressor cells and post-radiation wound-healing. The results demonstrate that SIRPα is a master regulator underlying tumor resistance to RT and provide proof-of-principle for SIRPα-deficient macrophage-based therapies to treat a broad spectrum of cancers, including those at advanced stages with low immunogenicity and metastases.

Correction to: Ionizing radiation modulates the phenotype and function of human CD4+ induced regulatory T cells.

An amendment to this paper has been published and can be accessed via the original article.

Ionizing radiation modulates the phenotype and function of human CD4+ induced regulatory T cells.

BACKGROUND: The use of immunotherapy strategies for the treatment of advanced cancer is rapidly increasing. Most immunotherapies rely on induction of CD8+ tumor-specific cytotoxic T cells that are capable of directly killing cancer cells. Tumors, however, utilize a variety of mechanisms that can suppress anti-tumor immunity. CD4+ regulatory T cells can directly inhibit cytotoxic T cell activity and these cells can be recruited, or induced, by cancer cells allowing escape from immune attack. The use of ionizing radiation as a treatment for cancer has been shown to enhance anti-tumor immunity by several mechanisms including immunogenic tumor cell death and phenotypic modulation of tumor cells. Less is known about the impact of radiation directly on suppressive regulatory T cells. In this study we investigate the direct effect of radiation on human TREG viability, phenotype, and suppressive activity. RESULTS: Both natural and TGF-ß1-induced CD4+ TREG cells exhibited increased resistance to radiation (10 Gy) as compared to CD4+ conventional T cells. Treatment, however, decreased Foxp3 expression in natural and induced TREG cells and the reduction was more robust in induced TREGS. Radiation also modulated the expression of signature iTREG molecules, inducing increased expression of LAG-3 and decreased expression of CD25 and CTLA-4. Despite the disconcordant modulation of suppressive molecules, irradiated iTREGS exhibited a reduced capacity to suppress the proliferation of CD8+ T cells. CONCLUSIONS: Our findings demonstrate that while human TREG cells are more resistant to radiation-induced death, treatment causes downregulation of Foxp3 expression, as well as modulation in the expression of TREG signature molecules associated with suppressive activity. Functionally, irradiated TGF-ß1-induced TREGS were less effective at inhibiting CD8+ T cell proliferation. These data suggest that doses of radiotherapy in the hypofractionated range could be utilized to effectively target and reduce TREG activity, particularly when used in combination with cancer immunotherapies.

NAD-linked mechanisms of gene de-repression and a novel role for CtBP in persistent adenovirus infection of lymphocytes.

BACKGROUND: Adenovirus (AdV) infection is ubiquitous in the human population and causes acute infection in the respiratory and gastrointestinal tracts. In addition to lytic infections in epithelial cells, AdV can persist in a latent form in mucosal lymphocytes, and nearly 80% of children contain viral DNA in the lymphocytes of their tonsils and adenoids. Reactivation of latent AdV is thought to be the source of deadly viremia in pediatric transplant patients. Adenovirus latency and reactivation in lymphocytes is not well studied, though immune cell activation has been reported to promote productive infection from latency. Lymphocyte activation induces global changes in cellular gene expression along with robust changes in metabolic state. The ratio of free cytosolic NAD+/NADH can impact gene expression via modulation of transcriptional repressor complexes. The NAD-dependent transcriptional co-repressor C-terminal Binding Protein (CtBP) was discovered 25 years ago due to its high affinity binding to AdV E1A proteins, however, the role of this interaction in the viral life cycle remains unclear. METHODS: The dynamics of persistently- and lytically-infected cells are evaluated. RT-qPCR is used to evaluate AdV gene expression following lymphocyte activation, treatment with nicotinamide, or disruption of CtBP-E1A binding. RESULTS: PMA and ionomycin stimulation shifts the NAD+/NADH ratio in lymphocytic cell lines and upregulates viral gene expression. Direct modulation of NAD+/NADH by nicotinamide treatment also upregulates early and late viral transcripts in persistently-infected cells. We found differential expression of the NAD-dependent CtBP protein homologs between lymphocytes and epithelial cells, and inhibition of CtBP complexes upregulates AdV E1A expression in T lymphocyte cell lines but not in lytically-infected epithelial cells. CONCLUSIONS: Our data provide novel insight into factors that can regulate AdV infections in activated human lymphocytes and reveal that modulation of cellular NAD+/NADH can de-repress adenovirus gene expression in persistently-infected lymphocytes. In contrast, disrupting the NAD-dependent CtBP repressor complex interaction with PxDLS-containing binding partners paradoxically alters AdV gene expression. Our findings also indicate that CtBP activities on viral gene expression may be distinct from those occurring upon metabolic alterations in cellular NAD+/NADH ratios or those occurring after lymphocyte activation.

Epigenetics and the dynamics of chromatin during adenovirus infections.

The DNA genome of eukaryotic cells is compacted by histone proteins within the nucleus to form chromatin. Nuclear-replicating viruses such as adenovirus have evolved mechanisms of chromatin manipulation to promote infection and subvert host defenses. Epigenetic factors may also regulate persistent adenovirus infection and reactivation in lymphoid tissues. In this review, we discuss the viral proteins E1A and protein VII that interact with and alter host chromatin, as well as E4orf3, which separates host chromatin from sites of viral replication. We also highlight recent advances in chromatin technologies that offer new insights into virus-directed chromatin manipulation. Beyond the role of chromatin in the viral replication cycle, we discuss the nature of persistent viral genomes in lymphoid tissue and cell lines, and the potential contribution of epigenetic signals in maintaining adenovirus in a quiescent state. By understanding the mechanisms through which adenovirus manipulates host chromatin, we will understand new aspects of this ubiquitous virus and shed light on previously unknown aspects of chromatin biology.

Effector function of CTLs is increased by irradiated colorectal tumor cells that modulate OX-40L and 4-1BBL and is reversed following dual blockade.

BACKGROUND: Sub-lethal doses of ionizing radiation (IR) can alter the phenotype of target tissue by modulating genes that influence effector T cell activity. Previous studies indicate that cancer cells respond to radiation by up-regulating surface expression of death receptors, cell adhesion molecules and tumor-associated antigens (TAA). However, there is limited information available regarding how T cells themselves are altered following these interactions with irradiated tumor cells. METHODS: Here, several human colorectal tumor cell lines were exposed to radiation (0-10 Gy) in vitro and changes in the expression of molecules costimulatory to effector T cells (4-1BBL, OX-40L, CD70, ICOSL) were examined by flow cytometry. T cell effector function was assessed to determine if changes in these proteins were directly related to the changes in T cell function. RESULTS: We found OX-40L and 4-1BBL to be the most consistently upregulated proteins on the surface of colorectal tumor cells post-IR while ICOSL and CD70 remained largely unaltered. Expression of these gene products correlated with enhanced killing of irradiated human colorectal tumor cells by TAA-specific T-cells. Importantly, blocking of both OX-40L and 4-1BBL reversed radiation-enhanced T-cell killing of human tumor targets as well as T-cell survival and activation. CONCLUSIONS: Overall, results of this study suggest that, beyond simply rendering tumor cells more sensitive to immune attack, radiation can be used to specifically modulate expression of genes that directly stimulate effector T cell activity.

Immunomodulatory effects of radiation: what is next for cancer therapy?

Despite its former reputation as being immunosuppressive, it has become evident that radiation therapy can enhance antitumor immune responses. This quality can be harnessed by utilizing radiation as an adjuvant to cancer immunotherapies. Most studies combine the standard radiation dose and regimens indicated for the given disease state, with novel cancer immunotherapies. It has become apparent that low-dose radiation, as well as doses within the hypofractionated range, can modulate tumor cells making them better targets for immune cell reactivity. Herein, we describe the range of phenotypic changes induced in tumor cells by radiation, and explore the diverse mechanisms of immunogenic modulation reported at these doses. We also review the impact of these doses on the immune cell function of cytotoxic cells in vivo and in vitro.

Combination Treatment with Sublethal Ionizing Radiation and the Proteasome Inhibitor, Bortezomib, Enhances Death-Receptor Mediated Apoptosis and Anti-Tumor Immune Attack.

Sub-lethal doses of radiation can modulate gene expression, making tumor cells more susceptible to T-cell-mediated immune attack. Proteasome inhibitors demonstrate broad anti-tumor activity in clinical and pre-clinical cancer models. Here, we use a combination treatment of proteasome inhibition and irradiation to further induce immunomodulation of tumor cells that could enhance tumor-specific immune responses. We investigate the effects of the 26S proteasome inhibitor, bortezomib, alone or in combination with radiotherapy, on the expression of immunogenic genes in normal colon and colorectal cancer cell lines. We examined cells for changes in the expression of several death receptors (DR4, DR5 and Fas) commonly used by T cells for killing of target cells. Our results indicate that the combination treatment resulted in increased cell surface expression of death receptors by increasing their transcript levels. The combination treatment further increases the sensitivity of carcinoma cells to apoptosis through FAS and TRAIL receptors but does not change the sensitivity of normal non-malignant epithelial cells. Furthermore, the combination treatment significantly enhances tumor cell killing by tumor specific CD8⁺ T cells. This study suggests that combining radiotherapy and proteasome inhibition may simultaneously enhance tumor immunogenicity and the induction of antitumor immunity by enhancing tumor-specific T-cell activity.

Radiation-induced modulation of immunogenic genes in tumor cells is regulated by both histone deacetylases and DNA methyltransferases.

Radiation treatment is a pivotal therapy for several cancer types, including colorectal cancer. It has been shown that sublethal doses of radiation modulate gene expression, making tumor cells more susceptible to T-cell-mediated immune attack. We have recently shown that low dose radiation enhances expression of multiple death receptors (Fas, DR4 and DR5) and co-stimulatory molecules (4-1BBL and OX-40L) in colorectal cancer (CRC) cells; however, it is unclear how ionizing radiation (IR) enhances expression of these molecules mechanistically. In the present study, we elucidate the molecular mechanisms by which radiation controls expression of these molecules in CRC. Here we report that, enhanced expression of these genes following radiation treatment of CRC cells is due, in part, to changes in DNA methylation and histone acetylation. We observed that radiation (5 Gy) significantly increased histone acetylation at the promoter regions of 4-1BBL, Fas and DR5 but not OX-40L. However, radiation did not induce changes in the global levels of acetylated histone H3 suggesting specificity of IR-induced changes. Furthermore, evaluation of epigenetic controlling enzymes revealed that IR did not alter overall cellular levels of HDACs (HDAC1, HDAC2 or HDAC3) or DNMTs (DNMT1, DNMT3a, or DNMT3b). Instead, radiation decreased binding of HDAC2 and HDAC3 at the promoter regions of Fas and 4-1BBL, respectively. Radiation also resulted in reduced DNMT1 at both the Fas and 4-1BBL promoter regions but not a control gene. We conclude that single dose radiation can influence the expression of immune response relevant genes in colorectal tumor cells by altering the binding of epigenetic enzymes, and modulating histone acetylation, at specific gene promoters.

Combination regimens of radiation therapy and therapeutic cancer vaccines: mechanisms and opportunities.

Radiation therapy (RT) is widely used with curative or palliative intent in the clinical management of multiple cancers. Although mainly aimed at direct tumor cell killing, mounting evidence suggests that radiation can alter the tumor to become an immunostimulatory milieu. Data suggest that the immunogenic effects of radiation can be exploited to promote synergistic antitumor effects in combination with immunotherapeutic agents. We review concepts associated with the immunogenic consequences of RT and highlight how preclinical findings are translating into clinical benefit for patients receiving combination regimens of RT and therapeutic cancer vaccines.

Turning T cells on: epigenetically enhanced expression of effector T-cell costimulatory molecules on irradiated human tumor cells.

BACKGROUND: Sub-lethal doses of radiation can alter the phenotype of target tissue by modulating gene expression and making tumor cells more susceptible to T-cell-mediated immune attack. We have previously shown that sub-lethal tumor cell irradiation enhances killing of colorectal carcinoma cells by tumor-specific cytotoxic T cells by unknown mechanisms. Recent data from our lab indicates that irradiation of tumor cells results in the upregulation of OX40L and 41BBL, and that T cells incubated with irradiated tumor cells displayed improved CTL survival, activation and effector activity. The objective of this current study was to determine the mechanism of enhanced OX40L and 41BBL expression in human colorectal tumor cells. METHODS: Two colorectal carcinoma cell lines, HCT116 and SW620, were examined for changes in the expression of 41BBL and OX40L in response to inhibition of histone deacetylases (using TSA) and DNA methyltransferases (using 5-Aza-2'-deoxycytidine) to evaluate if epigenetic mechanisms of gene expression can modulate these genes. Tumor cells were treated with radiation, TSA, or 5-Aza-dC, and subsequently evaluated for changes in gene expression using RT-qPCR and flow cytometry. Moreover, we assessed levels of histone acetylation at the 41BBL promoter using chromatin immunoprecipitation assays in irradiated HCT116 cells. RESULTS: Our data indicate that expression of 41BBL and OX40L can indeed be epigenetically regulated, as inhibition of histone deacetylases and of DNA methyltransferases results in increased OX40L and 41BBL mRNA and protein expression. Treatment of tumor cells with TSA enhanced the expression of these genes more than treatment with 5-Aza-dC, and co-incubation of T cells with TSA-treated tumor cells enhanced T-cell survival and activation, similar to radiation. Furthermore, chromatin immunoprecipitation experiments revealed significantly increased histone H3 acetylation of 41BBL promoters specifically following irradiation. CONCLUSIONS: Full understanding of specific mechanisms of immunogenic modulation (altered expression of immune relevant genes) of irradiated tumor cells will be required to determine how to best utilize radiation as a tool to enhance cancer immunotherapy approaches. Overall, our results suggest that radiation can be used to make human tumors more immunogenic through epigenetic modulation of genes stimulatory to effector T-cells.

Sub-lethal irradiation of human colorectal tumor cells imparts enhanced and sustained susceptibility to multiple death receptor signaling pathways.

BACKGROUND: Death receptors (DR) of the TNF family function as anti-tumor immune effector molecules. Tumor cells, however, often exhibit DR-signaling resistance. Previous studies indicate that radiation can modify gene expression within tumor cells and increase tumor cell sensitivity to immune attack. The aim of this study is to investigate the synergistic effect of sub-lethal doses of ionizing radiation in sensitizing colorectal carcinoma cells to death receptor-mediated apoptosis. METHODOLOGY/PRINCIPAL FINDINGS: The ability of radiation to modulate the expression of multiple death receptors (Fas/CD95, TRAILR1/DR4, TRAILR2/DR5, TNF-R1 and LTßR) was examined in colorectal tumor cells. The functional significance of sub-lethal doses of radiation in enhancing tumor cell susceptibility to DR-induced apoptosis was determined by in vitro functional sensitivity assays. The longevity of these changes and the underlying molecular mechanism of irradiation in sensitizing diverse colorectal carcinoma cells to death receptor-mediated apoptosis were also examined. We found that radiation increased surface expression of Fas, DR4 and DR5 but not LTßR or TNF-R1 in these cells. Increased expression of DRs was observed 2 days post-irradiation and remained elevated 7-days post irradiation. Sub-lethal tumor cell irradiation alone exhibited minimal cell death, but effectively sensitized three of three colorectal carcinoma cells to both TRAIL and Fas-induced apoptosis, but not LTßR-induced death. Furthermore, radiation-enhanced Fas and TRAIL-induced cell death lasted as long as 5-days post-irradiation. Specific analysis of intracellular sensitizers to apoptosis indicated that while radiation did reduce Bcl-X(L) and c-FLIP protein expression, this reduction did not correlate with the radiation-enhanced sensitivity to Fas and/or TRAIL mediated apoptosis among the three cell types. CONCLUSIONS/SIGNIFICANCE: Irradiation of tumor cells can overcome Fas and TRAIL resistance that is long lasting. Overall, results of these investigations suggest that non-lethal doses of radiation can be used to make human tumors more amenable to attack by anti-tumor effector molecules and cells.