Inhibition of DNMTs increases neoantigen-reactive T-cell toxicity against microsatellite-stable colorectal cancer in combination with radiotherapy

The therapeutic efficacy of immunotherapy is limited in the majority of colorectal cancer patients due to the low mutational and neoantigen burdens in this immunogenically "cold" microsatellite stability-colorectal cancer (MSS-CRC) cohort. Here, we showed that DNA methyltransferase (DNMT) inhibition upregulated neoantigen-bearing gene expression in MSS-CRC, resulting in increased neoantigen presentation by MHC class I in tumor cells and leading to increased neoantigen-specific T-cell activation in combination with radiotherapy. The cytotoxicity of neoantigen-reactive T cells (NRTs) to DNMTi-treated cancer cells was highly cytotoxic, and these cells secreted high IFNγ levels targeting MSS-CRC cells after ex vivo expansion of NRTs with DNMTi-treated tumor antigens. Moreover, the therapeutic efficacy of NRTs further increased when NRTs were combined with radiotherapy in vivo. Administration of DNMTi-augmented NRTs and radiotherapy achieved an ∼50 % complete response and extended survival time in an immunocompetent MSS-CRC animal model. Moreover, remarkably, splenocytes from these mice exhibited neoantigen-specific T-cell responses, indicating that radiotherapy in combination with DNMTi-augmented NRTs prolonged and increased neoantigen-specific T-cell toxicity in MSS-CRC patients. In addition, these DNMTi-augmented NRTs markedly increase the therapeutic efficacy of cancer vaccines and immune checkpoint inhibitors (ICIs). These data suggest that a combination of radiotherapy and epi-immunotherapeutic agents improves the function of ex vivo-expanded neoantigen-reactive T cells and increases the tumor-specific cytotoxic effector population to enhance therapeutic efficacy in MSS-CRC.

Neoantigen-augmented iPSC cancer vaccine combined with radiotherapy promotes antitumor immunity in poorly immunogenic cancers

Although irradiated induced-pluripotent stem cells (iPSCs) as a prophylactic cancer vaccine elicit an antitumor immune response, the therapeutic efficacy of iPSC-based cancer vaccines is not promising due to their insufficient antigenicity and the immunosuppressive tumor microenvironment. Here, we found that neoantigen-engineered iPSC cancer vaccines can trigger neoantigen-specific T cell responses to eradicate cancer cells and increase the therapeutic efficacy of RT in poorly immunogenic colorectal cancer (CRC) and triple-negative breast cancer (TNBC). We generated neoantigen-augmented iPSCs (NA-iPSCs) by engineering AAV2 vector carrying murine neoantigens and evaluated their therapeutic efficacy in combination with radiotherapy. After administration of NA-iPSC cancer vaccine and radiotherapy, we found that ~60% of tumor-bearing mice achieved a complete response in microsatellite-stable CRC model. Furthermore, splenocytes from mice treated with NA-iPSC plus RT produced high levels of IFNγ secretion in response to neoantigens and had a greater cytotoxicity to cancer cells, suggesting that the NA-iPSC vaccine combined with radiotherapy elicited a superior neoantigen-specific T-cell response to eradicate cancer cells. The superior therapeutic efficacy of NA-iPSCs engineered by mouse TNBC neoantigens was also observed in the syngeneic immunocompetent TNBC mouse model. We found that the risk of spontaneous lung and liver metastasis was dramatically decreased by NA-iPSCs plus RT in the TNBC animal model. Altogether, these results indicated that autologous iPSC cancer vaccines engineered by neoantigens can elicit a high neoantigen-specific T-cell response, promote tumor regression, and reduce the risk of distant metastasis in combination with local radiotherapy.

Colorectal cancer-specific IFNβ delivery overcomes dysfunctional dsRNA-mediated type I interferon signaling to increase the abscopal effect of radiotherapy

BACKGROUND

Cancer-intrinsic type I interferon (IFN-I) production triggered by radiotherapy (RT) is mainly dependent on cytosolic double-stranded DNA (dsDNA)-mediated cGAS/STING signaling and increases cancer immunogenicity and enhances the antitumor immune response to increase therapeutic efficacy. However, cGAS/STING deficiency in colorectal cancer (CRC) may suppress the RT-induced antitumor immunity. Therefore, we aimed to evaluate the importance of the dsRNA-mediated antitumor immune response induced by RT in patients with CRC.

METHODS

Cytosolic dsRNA level and its sensors were evaluated via cell-based assays (co-culture assay, confocal microscopy, pharmacological inhibition and immunofluorescent staining) and in vivo experiments. Biopsies and surgical tissues from patients with CRC who received preoperative chemoradiotherapy (neoCRT) were collected for multiplex cytokine assays, immunohistochemical analysis and SNP genotyping. We also generated a cancer-specific adenovirus-associated virus (AAV)-IFNβ1 construct to evaluate its therapeutic efficacy in combination with RT, and the immune profiles were analyzed by flow cytometry and RNA-seq.

RESULTS

Our studies revealed that RT stimulates the autonomous release of dsRNA from cancer cells to activate TLR3-mediated IFN-I signatures to facilitate antitumor immune responses. Patients harboring a dysfunctional TLR3 variant had reduced serum levels of IFN-I-related cytokines and intratumoral CD8+ immune cells and shorter disease-free survival following neoCRT treatment. The engineered cancer-targeted construct AAV-IFNβ1 significantly improved the response to RT, leading to systematic eradication of distant tumors and prolonged survival in defective TLR3 preclinical models.

CONCLUSION

Our results support that increasing cancer-intrinsic IFNβ1 expression is an immunotherapeutic strategy that enhances the RT-induced antitumor immune response in locally patients with advanced CRC with dysfunctional TLR3.

Activation of STING by the novel liposomal TLC388 enhances the therapeutic response to anti-PD-1 antibodies in combination with radiotherapy

Current immune checkpoint inhibiters (ICIs) have contrasting clinical results in poorly immunogenic cancers such as microsatellite-stable colorectal cancer (MSS-CRC). Therefore, understanding and developing the combinational therapeutics for ICI-unresponsive cancers is critical. Here, we demonstrated that the novel topoisomerase I inhibitor TLC388 can reshape the tumor immune landscape, corroborating their antitumor effects combined with radiotherapy as well as immunotherapy. We found that TLC388 significantly triggered cytosolic single-stranded DNA (ssDNA) accumulation for STING activation, leading to type I interferons (IFN-Is) production for increased cancer immunogenicity to enhance antitumor immunity. TLC388-treated tumors were infiltrated by a vast number of dendritic cells, immune cells, and costimulatory molecules, contributing to the favorable antitumor immune response within the tumor microenvironment. The infiltration of cytotoxic T and NK cells were more profoundly existed within tumors in combination with radiotherapy and ICIs, leading to superior therapeutic efficacy in poorly immunogenic MSS-CRC. Taken together, these results showed that the novel topoisomerase I inhibitor TLC388 increased cancer immunogenicity by ssDNA/STING-mediated IFN-I production, enhancing antitumor immunity for better therapeutic efficacy in combination with radiotherapy and ICIs for poorly immunogenic cancer.

Dual Inhibition of B7-H3 and EGFR Overcomes Acquired Chemoresistance in Colon Adenocarcinoma

Despite advances in therapeutic strategies for colorectal cancer (CRC), CRC has a high disease incidence with significant morbidity and mortality worldwide. Notably, immunotherapy has shown limited efficacy in treating metastatic CRC, underscoring the need for alternative immunotherapeutic targets for the management of metastatic colorectal cancer (mCRC). In the present study, we evaluated the levels of the immune checkpoint proteins PD-L1, PD-L2 and B7-H3 in a large cohort retrospective study. We found that tumor B7-H3 (52.7%) was highly expressed in primary tumors compared to that in PD-L1 (33.6%) or PD-L2 (34.0%). Elevated B7-H3 expression was associated with advanced stage and the risk of distant metastasis and correlated with poor disease-free survival (DFS), suggesting that tumor B7-H3 was an independent prognostic factor associated with worse DFS in colon adenocarcinoma patients (COAD), especially high-risk COAD patients who received adjuvant chemotherapy. Furthermore, we found that B7-H3 significantly promoted cell proliferation and tumor growth in CRC. B7-H3 may stabilize EGFR to activate its downstream pathway for cancer cell proliferation and resistance to oxaliplatin (OXP). Dual targeting of B7-H3 and EGFR markedly rescued the susceptibility to chemotherapy in colorectal cancer cells in vitro and in vivo. Overall, these results showed that B7-H3 exhibited a high prevalence in COAD patients and was significantly associated with worse prognosis in COAD patients. Dual targeting of B7-H3 and EGFR signaling might be a potential therapeutic strategy for high-risk COAD patients.

Prognostic Value of Immune Cells Subsets Within the Tumor Microenvironment in Patients With Rectal Adenocarcinoma

BACKGROUND/AIM

One-third of newly diagnosed colorectal cancer cases are rectal cancers. Multimodal treatment regimens including surgery, radiotherapy, and chemotherapy improve local control and survival outcome and decrease tumor relapse for patients with rectal adenocarcinoma (READ). However, stratification of patients to predict their responses is urgently needed to improve therapeutic responses.

PATIENTS AND METHODS

Immunostainings of CD3+, CD8+, and CD45RO+ immune cell subsets within the tumor microenvironment were evaluated using immunohistochemistry in two hundred seventy-nine READ patients.

RESULTS

In this study, we found that examination of the adaptive immune response by quantifying CD3+, CD8+, and CD45RO+ immune cell subsets, provides improved and independent prognostic value for patients with READ. Regardless of conventional clinical and pathologic parameters, the densities of T cell subsets were strongly related to a better prognosis in patients with READ. High density of intratumoral immune cells is associated with absence of nodal metastasis, lymphovascular invasion, and perineural invasion. Moreover, high tumor-infiltrating lymphocyte (TIL) subsets were associated with favorable survival outcome in patients with READ, especially high-risk patients with advanced READ.

CONCLUSION

Immune cell subsets including CD3, CD8, and CD45RO within the tumor microenvironment were independent prognostic factors for patients with READ.

TNFα modulates PANX1 activation to promote ATP release and enhance P2RX7-mediated antitumor immune responses after chemotherapy in colorectal cancer

ATP and its receptor P2RX7 exert a pivotal effect on antitumor immunity during chemotherapy-induced immunogenic cell death (ICD). Here, we demonstrated that TNFα-mediated PANX1 cleavage was essential for ATP release in response to chemotherapy in colorectal cancer (CRC). TNFα promoted PANX1 cleavage via a caspase 8/3-dependent pathway to enhance cancer cell immunogenicity, leading to dendritic cell maturation and T-cell activation. Blockade of the ATP receptor P2RX7 by the systemic administration of small molecules significantly attenuated the therapeutic efficacy of chemotherapy and decreased the infiltration of immune cells. In contrast, administration of an ATP mimic markedly increased the therapeutic efficacy of chemotherapy and enhanced the infiltration of immune cells in vivo. High PANX1 expression was positively correlated with the recruitment of DCs and T cells within the tumor microenvironment and was associated with favorable survival outcomes in CRC patients who received adjuvant chemotherapy. Furthermore, a loss-of-function P2RX7 mutation was associated with reduced infiltration of CD8+ immune cells and poor survival outcomes in patients. Taken together, these results reveal that TNFα-mediated PANX1 cleavage promotes ATP-P2RX7 signaling and is a key determinant of chemotherapy-induced antitumor immunity.

Dysfunctional TLR1 reduces the therapeutic efficacy of chemotherapy by attenuating HMGB1-mediated antitumor immunity in locally advanced colorectal cancer

Regional lymph node metastasis is an important predictor for survival outcome and an indicator for postoperative adjuvant chemotherapy in patients with colorectal cancer. Even with advances in adjuvant chemotherapeutic regimens, 5-year distant metastasis and survival rates are still unsatisfactory. Here, we evaluate the clinical significance of polymorphisms in receptors for HMGB1, which is the hallmark of chemotherapy-induced immunogenic cell death, in patients with stage II-III colon carcinoma (COAD). We found that high cytosolic HMGB1 is elicited in stage III COAD patients who received adjuvant chemotherapy. Patients with the TLR1-N248S polymorphism (rs4833095), which causes loss-of-function in HMGB1-mediated TLR1-TLR2 signaling, may influence the therapeutic efficacy of adjuvant chemotherapy, leading to a high risk of distant metastasis within 5 years [HR = 1.694, 95% CI = 1.063-2.698, p = 0.027], suggesting that TLR1-N248S is an independent prognostic factor for locally advanced colon carcinoma patients. We found that defective TLR1 impaired TLR1/2 signaling during dendritic cell (DC) maturation for the antitumor immune response under immunogenic chemotherapy oxaliplatin (OXP) treatment. Defective TLR1 on DCs impaired their maturation ability by HMGB1 and reduced the secretion of IFNγ from T cells to eradicate tumor cells in vitro. Moreover, systemic inhibition of TLR1/2 dramatically reduced the tumor-infiltrating immune cells by OXP treatment, leading to poor therapeutic response to OXP. In contrast, administration of a TLR1/2 agonist synergistically increased the benefit of OXP treatment and triggered a high density of tumor-infiltrating immune cells. We also observed that fewer tumor-infiltrating cytotoxic T lymphocytes were located within the tumor microenvironment in patients bearing the TLR1-N248S polymorphism. Overall, our results suggest that dysfunctional TLR1 may reduce the therapeutic response to adjuvant chemotherapy by impairing HMGB1-mediated DC maturation and attenuating the antitumor immune response in locally advanced colon carcinoma patients.

Neoantigen Cancer Vaccine for Immunologically Cold Microsatellite-stable Colorectal Cancer

PURPOSE/OBJECTIVE(S)

Immunotherapies, such as immune checkpoint inhibitors (ICIs), have revolutionized management of some cancers but have little benefit for microsatellite-stable colorectal cancer patients (MSS-CRC). This is, in part, due to the low mutations and neoantigen expression in this immunogenically "cold" MSS-CRC. Therefore, we aim to develop novel shared neoantigen-based therapeutic cancer vaccine to reinvigorate antitumor immunity and enhance the therapeutic benefit of radiotherapy in MSS-CRC.

MATERIALS/METHODS

To identify novel highly expressed and shared neoantigens, we collected 40 match-paired adjacent normal and tumor tissues from MSS-CRC patients for WES-seq, RNA-seq, and liquid chromatography-MS/MS (LC-MS/MS). By incorporating these databases, we established Neoantigen Discovery and Validation (NeoDiva) system to identify a cluster of highly expressed and shared neoantigens derived from non-coding regions and evaluate its immunogenicity by HLA-A*11 transgenic mice. We then develop a neoantigen-based therapeutic cancer vaccine by an engineered adenovirus-associated virus (AAV) to evaluate its therapeutic efficacy in combination with radiotherapy in MSS-CRC animal model.

RESULTS

We identified a cluster of highly expressed and shared neoantigens (HLA-A*11-restricted) derived from non-coding regions. The immunogenicity of these novel neoantigens was demonstrated by HLA-A*11 transgenic mice and ex vivo stimulation. Moreover, the engineered AAV-based neoantigen cancer vaccine significantly eradicates cancer cells, prevents distant metastasis, prolong survival period in combination with radiotherapy. By flow cytometry, ELISPOT and MHC-I-tetramer assay, we demonstrated the recruitment of tumor-infiltrating lymphocytes was remarkably increased and neoantigen-specific T cell response was enhanced. Moreover, these isolated neoantigen-specific T cells can recognize cancer cells and produce IFNg to kill cancer cells.

CONCLUSION

Neoantigens identified by our NeoDiVa platform, via the combination of radiotherapy and a novel AAV vaccine delivery system, boosted antigen-specific T-cell function and improve tumor control of limnologically "cold" MSS colorectal cancer in vivo. We are in the process of obtaining an IND and initiating Phase I/II clinical trial to validate safety and efficacy of these exciting findings.

Impact of Pattern Recognition Receptors on the Prognosis of Chemotherapy-treated Rectal Cancer Patients

BACKGROUND/AIM

Chemotherapeutic drugs or radiation can cause immunogenic cell death (ICD) and damage-associated molecular pattern (DAMP) release to activate pattern recognition receptor (PRR) in immune cells. Several PRRs bridge innate immunity and adaptive immunity and are implicated in the anticancer immune response. However, single nucleotide polymorphisms (SNPs) in PRRs are associated with chemotherapeutic drugs or radiation response in cancer treatment.

PATIENTS AND METHODS

We enrolled 117 patients with rectal cancer who received surgery with or without postoperative chemotherapy and examined the SNPs in PRRs from formalin-fixed, paraffin embedded tissues. The genotypes of RAGE (G82S/rs2070600), P2RX7 (E496A/rs3751143), and FPR1 (E346A/rs867228) were determined and analyzed using the MassARRAY platform.

RESULTS

We integrated the status of PRR polymorphism into the PRR score and found that the PRR score was significantly associated with 10-year disease-free survival (DFS) (p=0.025) in patients with rectal cancer. Moreover, the PRR score was an independent risk factor for 10-year DFS (HR=4.400, 95%CI=1.607-12.212, p=0.004) and 10-year overall survival (OS) (HR=4.674, 95%CI=1.423-16.038, p=0.011) in patients with rectal cancer treated postoperatively with adjuvant chemotherapy.

CONCLUSION

The PRR score is an independent prognostic factor for the survival outcome of patients with rectal cancer, especially those treated postoperatively with adjuvant chemotherapy. PRR score evaluation may be used as a biomarker in the clinic.

Health Economic Evaluation of Proton Therapy for Lung Cancer: A Systematic Review

BACKGROUND

To our knowledge, there have been no systematic reviews of health economic evaluations of proton therapy specific to lung cancer.

METHODS

We conducted this systematic review according to the predefined protocol [PROSPERO CRD42022365869]. We summarized the results of the included studies via structured narrative synthesis.

RESULTS

We identified four studies (all used passively scattered proton therapy) from 787 searches. Two cost analyses reported that proton therapy was more costly than photon therapy for early- or locally advanced-stage non-small cell lung cancer, one cost-utility analysis reported that proton therapy was dominated by nonproton therapy in early-stage non-small cell lung cancer, and one cost-utility analysis reported that proton therapy was not cost-effective (vs. photon) in locally advanced non-small cell lung cancer.

CONCLUSIONS

Passively scattered proton therapy was more costly and not cost-effective than photon therapy for early- and locally advanced-stage non-small cell lung cancer. Further health economic evaluations regarding modern proton therapy (such as scanning beam) for common radiotherapy indications of lung cancer are eagerly awaited.

Targeting CD73 increases therapeutic response to immunogenic chemotherapy by promoting dendritic cell maturation

The CD39-CD73-adenosinergic pathway converts adenosine triphosphate (ATP) to adenosine for inhibiting anti-tumor immune responses. Therefore, targeting CD73 to reinvigorate anti-tumor immunity is considered the novel cancer immunotherapy to eradicate tumor cells. To fully understand the critical role of CD39/CD73 in colon adenocarcinoma (COAD), this study aims to comprehensive investigate the prognostic significance of CD39 and CD73 in stage I-IV COAD. Our data demonstrated that CD73 staining strongly marked malignant epithelial cells and CD39 was highly expressed in stromal cells. Attractively, tumor CD73 expression was significantly associated with tumor stage and the risk of distant metastasis, which suggested CD73 was as an independent factor for colon adenocarcinoma patients in univariate COX analysis [HR = 1.465, 95%CI = 1.084-1.978, p = 0.013]; however, high stromal CD39 in COAD patients was more likely to have favorable survival outcome [HR = 1.458, p = 1.103-1.927, p = 0.008]. Notably, high CD73 expression in COAD patients showed poor response to adjuvant chemotherapy and high risk of distant metastasis. High CD73 expression was inversely associated with less infiltration of CD45⁺ and CD8⁺ immune cells. However, administration with anti-CD73 antibodies significantly increased the response to oxaliplatin (OXP). Blockade of CD73 signaling synergistically enhanced OXP-induced ATP release, which is a marker of immunogenic cell death (ICD), promotes dendritic cell maturation and immune cell infiltration. Moreover, the risk of colorectal cancer lung metastasis was also decreased. Taken together, the present study revealed tumor CD73 expression inhibited the recruitment of immune cells and correlated with a poor prognosis in COAD patients, especially patients received adjuvant chemotherapy. Targeting CD73 to markedly increased the therapeutic response to chemotherapy and inhibited lung metastasis. Therefore, tumor CD73 may be an independent prognostic factor as well as the potential of therapeutic target for immunotherapy to benefit colon adenocarcinoma patients.

A Novel Engineered AAV-Based Neoantigen Vaccine in Combination with Radiotherapy Eradicates Tumors

The potency of tumor-specific antigen (TSA) vaccines, such as neoantigen (neoAg)-based cancer vaccines, can be compromised by host immune checkpoint inhibitory mechanisms, such as programmed cell death protein 1 (PD-1)/programmed death ligand 1 (PD-L1), that attenuate neoAg presentation on dendritic cells (DC) and hinder T cell-mediated cytotoxicity. To overcome PD-1/PD-L1 inhibition in DCs, we developed a novel adeno-associated virus (meAAV) neoAg vaccine, modified with TLR9 inhibitory fragments, PD-1 trap, and PD-L1 miRNA, which extend the persistence of meAAV and activate neoAg-specific T-cell responses in immune-competent colorectal and breast cancer murine models. Moreover, we found that in combination with radiotherapy, the meAAV-based neoAg cancer vaccine not only elicited higher antigen presentation ability, but also maintained neoAg-specific cytotoxic T lymphocyte (CTL) responses. These functional PD-1 traps and PD-L1 miRNAs overcome host PD-1/PD-L1 inhibitory mechanisms and boost the therapeutic efficacy of radiotherapy. More importantly, combined radiotherapy and meAAV neoAg cancer vaccines significantly enhanced neoAg-specific CTL responses, increased CTL infiltration in tumor microenvironment, and decreased tumor-associated immunosuppression. This process led to the complete elimination of colorectal cancer and delayed tumor growth of breast cancer in tumor-bearing mice. Taken together, our results demonstrated a novel strategy that combines neoAg cancer vaccine and radiotherapy to increase the therapeutic efficacy against colorectal and breast cancers.

Engineered sTRAIL-armed MSCs overcome STING deficiency to enhance the therapeutic efficacy of radiotherapy for immune checkpoint blockade

Radiotherapy (RT) mainly elicits antitumor immunity via the cGAS/STING axis for type I interferon (IFN) production. However, dysregulation of cGAS/STING constrains radiotherapy-induced antitumor immunity and type I IFN-dependent cell death and is associated with shorter survival of patients with colorectal cancer (CRC). Due to their tumor tropism, mesenchymal stem cells (MSCs) have shown the potential to deliver therapeutic genes for cancer therapy. Here, we showed that MSCs enhance the sensitivity to RT by inducing TRAIL-dependent cell death and remodel the tumor microenvironment by recruiting CD8+ immune cells to upregulate PD-L1 in the tumor. By engineering MSCs to express CRC-specific soluble TRAIL via adenovirus-associated virus 2 (AAV2), we found that the therapeutic activity of MSC-sTRAIL was superior to that of MSCs alone when combined with RT. Combined treatment with MSC-sTRAIL and RT significantly reduced cell viability and increased apoptosis by inducing TRAIL-dependent cell death in STING-deficient colorectal cancer cells. MSC-sTRAIL directly triggered TRAIL-dependent cell death to overcome the deficiency of the cGAS/STING axis. Moreover, these combination treatments of MSC-sTRAIL and RT significantly remodeled the tumor microenvironment, which was more suitable for anti-PD-L1 immunotherapy. Taken together, this therapeutic strategy represents a novel targeted treatment option for patients with colorectal cancer, especially cGAS/STING-deficient patients.

Dual inhibition of TGFβ signaling and CSF1/CSF1R reprograms tumor-infiltrating macrophages and improves response to chemotherapy via suppressing PD-L1

TGFβ contributes to chemoresistance in advanced colorectal cancer (CRC) via diverse immune-microenvironment mechanisms. Here, we found that cancer cell autonomous TGFβ directly triggered tumor programmed cell death 1 ligand 1 (PD-L1) upregulation, resulting in resistance to chemotherapy. Inhibition of tumor PD-L1 expression sensitized cancer cells to chemotherapy, reduced lung metastasis and increased the influx of CD8⁺ T cells. However, chemorefractory cancer cell-derived CSF1 recruited TAMs for TGFβ-mediated PD-L1 upregulation via a vicious cycle. High infiltration of macrophages was clinically correlated with the status of tumor PD-L1 after chemotherapy treatment in CRC patients. We found that depletion of immunosuppressive CSF1R⁺ TAM infiltration and blockade of the TGFβ receptor resulted in an increased influx of cytotoxic CD8⁺ T and effector memory CD8⁺ cells, a reduction in regulatory T cells, and a synergistic inhibition of tumor growth when combined with chemotherapy. These findings show that CSF1R⁺ TAMs and TGFβ are the dominant components that regulate PD-L1 expression within the immunosuppressive tumor microenvironment, providing a therapeutic strategy for advanced CRC patients.

Protein phosphatase 2A inactivation induces microsatellite instability, neoantigen production and immune response

Microsatellite-instable (MSI), a predictive biomarker for immune checkpoint blockade (ICB) response, is caused by mismatch repair deficiency (MMRd) that occurs through genetic or epigenetic silencing of MMR genes. Here, we report a mechanism of MMRd and demonstrate that protein phosphatase 2A (PP2A) deletion or inactivation converts cold microsatellite-stable (MSS) into MSI tumours through two orthogonal pathways: (i) by increasing retinoblastoma protein phosphorylation that leads to E2F and DNMT3A/3B expression with subsequent DNA methylation, and (ii) by increasing histone deacetylase (HDAC)2 phosphorylation that subsequently decreases H3K9ac levels and histone acetylation, which induces epigenetic silencing of MLH1. In mouse models of MSS and MSI colorectal cancers, triple-negative breast cancer and pancreatic cancer, PP2A inhibition triggers neoantigen production, cytotoxic T cell infiltration and ICB sensitization. Human cancer cell lines and tissue array effectively confirm these signaling pathways. These data indicate the dual involvement of PP2A inactivation in silencing MLH1 and inducing MSI.

DNMT1 constrains IFNβ-mediated anti-tumor immunity and PD-L1 expression to reduce the efficacy of radiotherapy and immunotherapy

Radiotherapy can boost the therapeutic response to immune checkpoint inhibitors (ICIs) by recruiting T lymphocytes and upregulating PD-L1 expression within the tumor microenvironment (TME). However, in some cases, tumor PD-L1 expression cannot be induced, even in the presence of abundant T lymphocytes, in locally advanced colorectal cancer patients who receive preoperative neoadjuvant concurrent chemoradiotherapy (CCRT). In this study, we found that PD-L1 promoter methylation is negatively correlated with tumor PD-L1 expression and is an independent biomarker for locally advanced colorectal cancer patients. PD-L1 methylation (mCD274) was significantly associated with shorter disease-free survival (cg15837913 loci, p = .0124). By multivariate Cox proportional hazards analyses including influent factors, mCD274 was classified as an independent prognostic factor for poor 5-year DFS [cg15837913, hazard ratio: HR = 4.06, 95% CI = 1.407-11.716, p = .01]. We found that the immunomodulatory agent DNA methyltransferase inhibitor (DNMTi) led to demethylation of the PD-L1 promoter and increased radiotherapy-induced PD-L1 upregulation via interferon β (IFNβ). DNMTi not only induced tumor PD-L1 expression but increased the expression of immune-related genes as well as intratumoral T cell infiltration in vivo. Furthermore, DNMTi strongly enhanced the response to combined treatment with radiotherapy and anti-PD-L1 inhibitors, and prolonged survival in microsatellite stability (MSS) colorectal model. Therefore, DNMTi remodeled the tumor microenvironment to improve the effect of radiotherapy and anti-PD-L1 immunotherapy by directly triggering tumor PD-L1 expression and eliciting stronger immune responses, which may provide potential clinical benefits to colorectal cancer patients in the future.

An independent predictor of poor prognosis in locally advanced rectal cancer: rs867228 in formyl peptide receptor 1 (FPR1)

Formyl peptide receptor 1 (FPR1) plays a key regulatory role in innate and adaptive immunity. Recently, we reported that the CC genotype of FPR1-E346A (rs867228, c. 1037 A > C) is an independent biomarker for patients with locally advanced rectal cancer (LARC) who received preoperative concurrent chemoradiotherapy (CCRT). Pharmacologic inhibition of FPR1 decreased the migration and infiltration of T lymphocytes into tumor microenvironment after CCRT.

Polymorphism of formyl peptide receptor 1 (FPR1) reduces the therapeutic efficiency and antitumor immunity after neoadjuvant chemoradiotherapy (CCRT) treatment in locally advanced rectal cancer

Immunosurveillance and immunoscavenging prompted by preoperative chemoradiotherapy (CCRT) may contribute to improve local control and increase survival outcomes for patients with locally advanced rectal cancer (LARC). In this study, we investigated several genotypes of pattern recognition receptors (PRRs) and their impact on therapeutic efficacy in LARC patients treated with CCRT. We found that homozygosis of formyl peptide receptor 1 (FPR1) (E346A/rs867228) was associated with reduced 5-year overall survival (OS) by Kaplan-Meier analysis (62% vs. 81%, p = 0.014) and multivariate analysis [hazard ratio (HR) = 3.383, 95% CI = 1.374-10.239, p = 0.007]. Moreover, in an animal model, we discovered that the FPR1 antagonist, Boc-MLF (Boc-1), reduced CCRT therapeutic efficacy and decreased cytotoxic T cells and T effector memory cells after chemoradiotherapy treatment. Pharmacologic inhibition of FPR1 by Boc-1 decreased T lymphocyte migration to irradiated tumor cells. Therefore, these results revealed that the FPR1 genotype participates in CCRT-elicited anticancer immunity by reducing T lymphocytes migration and infiltration, and that the FPR1-E346A CC genotype can be considered an independent biomarker for chemo- and radiotherapy outcomes.

Decitabine Augments Chemotherapy-Induced PD-L1 Upregulation for PD-L1 Blockade in Colorectal Cancer

Programmed cell death-1 (PD-1) has demonstrated impressive clinical outcomes in several malignancies, but its therapeutic efficacy in the majority of colorectal cancers is still low. Therefore, methods to improve its therapeutic efficacy in colorectal cancer (CRC) patients need further investigation. Here, we demonstrate that immunogenic chemotherapeutic agents trigger the induction of tumor PD-L1 expression in vitro and in vivo, a fact which was validated in metastatic CRC patients who received preoperatively neoadjuvant chemotherapy (neoCT) treatment, suggesting that tumor PD-L1 upregulation by chemotherapeutic regimen is more feasible via PD-1/PD-L1 immunotherapy. However, we found that the epigenetic control of tumor PD-L1 via DNA methyltransferase 1 (DNMT1) significantly influenced the response to chemotherapy. We demonstrate that decitabine (DAC) induces DNA hypomethylation, which not only directly enhances tumor PD-L1 expression but also increases the expression of immune-related genes and intratumoral T cell infiltration in vitro and in vivo. DAC was found to profoundly enhance the therapeutic efficacy of PD-L1 immunotherapy to inhibit tumor growth and prolong survival in vivo. Therefore, it can be seen that DAC remodels the tumor microenvironment to improve the effect of PD-L1 immunotherapy by directly triggering tumor PD-L1 expression and eliciting stronger anti-cancer immune responses, providing potential clinical benefits to CRC patients in the future.

Removal of N-Linked Glycosylation Enhances PD-L1 Detection and Predicts Anti-PD-1/PD-L1 Therapeutic Efficacy

Reactivation of T cell immunity by PD-1/PD-L1 immune checkpoint blockade has been shown to be a promising cancer therapeutic strategy. However, PD-L1 immunohistochemical readout is inconsistent with patient response, which presents a clinical challenge to stratify patients. Because PD-L1 is heavily glycosylated, we developed a method to resolve this by removing the glycan moieties from cell surface antigens via enzymatic digestion, a process termed sample deglycosylation. Notably, deglycosylation significantly improves anti-PD-L1 antibody binding affinity and signal intensity, resulting in more accurate PD-L1 quantification and prediction of clinical outcome. This proposed method of PD-L1 antigen retrieval may provide a practical and timely approach to reduce false-negative patient stratification for guiding anti-PD-1/PD-L1 therapy.

Upregulation of tumor PD-L1 by neoadjuvant chemoradiotherapy (neoCRT) confers improved survival in patients with lymph node metastasis of locally advanced rectal cancers

The expression of programmed cell death 1 ligand 1 (PD-L1) and interferon-γ (IFN-γ) is of great interest for the development of chemoradiotherapy and immune checkpoint inhibitor treatments. Patients with nodal metastasis (pN+) tend to have a poor prognosis, even after neoadjuvant chemoradiotherapy (neoCRT) and surgical treatment. In this study, we examined the roles of tumor PD-L1 and IFN-γ before and after neoCRT in locally advanced rectal cancer (LARC) patients. Our results demonstrate that patients with high PD-L1 expression in post-neoCRT tissues exhibit improved 5-year disease-free survival (DFS) and overall survival (OS) compared with those with low PD-L1 expression (p < 0.001). Furthermore, in the pN+ population, patients with high PD-L1 expression in post-neoCRT tissues exhibit improved 5-year DFS and OS. PD-L1 and IFN-γ upregulation increased in tumor tissues after neoCRT, and patients with high PD-L1 and high IFN-γ exhibit improved 5-year DFS and OS (p = 0.04 and p = 0.001, respectively). To the best of our knowledge, this study is the first to demonstrate that PD-L1 upregulation in a pN+ cohort correlates with improved prognosis, which is similar to that in patients without nodal metastasis. Moreover, this study verified that PD-L1 and IFN-γ were upregulated by neoCRT treatment in LARC patients and demonstrated that neoCRT may be useful not only for immune checkpoint inhibitor treatment but also for reinvigorating preexisting anti-cancer immunity.

Clinical significance of programmed death 1 ligand-1 (CD274/PD-L1) and intra-tumoral CD8+ T-cell infiltration in stage II-III colorectal cancer

Programmed cell death-1 (PDCD1/PD-1) and its ligand programmed cell death 1 ligand 1 (CD274/PD-L1) have been reported to suppress anti-tumor T cell-mediated immune responses. However, the clinical significance of CD274 in colorectal cancer were still elusive. We aim to clarify the relationships between CD8+ intratumor-infiltrating lymphocytes (TILs) and CD274 as well as their prognostic values in stage II-III colon carcinoma. Tumor differentiation, perineural invasion (PNI), pN stage and DNA mismatch repair (MMR)-deficient were clearly correlated with CD8+ TILs counts within the tumor microenvironment (p < 0.0001). Furthermore, tumor differentiation and PNI were suggestively correlated with tumor CD274 expression (p = 0.02 and p = 0.0195). Tumor CD274 level was significantly correlated with higher CD8+ TILs (p < 0.0001) but was not associated with MMR-deficient status (p = 0.14). High tumor CD274 expression [hazard ratio (HR) = 2.16, 95% CI = 1.63-2.86, p < 0.0001] and CD8+ TILs [HR = 1.51, 95% CI = 1.19-1.91, p = 0.0007] were associated with improved disease-free survival and overall survival. Additionally, the subgroup of patients who had a high CD8+ TILs/tumor CD274 have better survival outcomes compared with other subgroups (71% vs 53%; p < 0.0001). Therefore, the CD8+ TILs counts and tumor CD274 may be prognostic factors to predict survival and therapeutic responses in stage II-III colon carcinoma patients.

Cytosolic high-mobility group box protein 1 (HMGB1) and/or PD-1+ TILs in the tumor microenvironment may be contributing prognostic biomarkers for patients with locally advanced rectal cancer who have undergone neoadjuvant chemoradiotherapy

Rectal cancer, which comprises 30% of all colorectal cancer cases, is one of the most common forms of cancer in the world. Patients with locally advanced rectal cancer (LARC) are often treated with neoadjuvant chemoradiotherapy (neoCRT) followed by surgery. However, after neoCRT treatment, approximately one-third of the patients progress to local recurrence or distant metastasis. In these studies, we found that patients with tumors that exhibited cytosolic HMGB1(Cyto-HMGB1) translocation and/or the presence of PD-1+ tumor-infiltrating lymphocytes (TILs) before treatment had a better clinical outcome. The better outcome is likely due to the release of HMGB1, which triggers the maturation of dendritic cells (DCs) via TLR4 activation, and the subsequent recruitment of PD-1+ tumor-infiltrating lymphocytes to the tumor site, where they participate in immune-scavenging. In conclusion, our results provide evidence that cyto-HMGB1 and/or PD-1+TIL are not only predictive biomarkers before treatment, but they can also potentially designate patients for personalized oncological management including immunotherapy.