Agonist immunotherapy restores T cell function following MEK inhibition improving efficacy in breast cancer

Beyond Anti-PD-1/PD-L1: Improving Immune Checkpoint Inhibitor Responses in Triple-Negative Breast Cancer

The introduction of anti-programmed cell death protein-1 (anti-PD-1) to the clinical management of triple-negative breast cancer (TNBC) represents a breakthrough for a disease whose treatment has long relied on the standards of chemotherapy and surgery. Nevertheless, few TNBC patients achieve a durable remission in response to anti-PD-1, and there is a need to develop strategies to maximize the potential benefit of immune checkpoint inhibition (ICI) for TNBC patients. In the present review, we discuss three conceptual strategies to improve ICI response rates in TNBC patients. The first effort involves improving patient selection. We discuss proposed biomarkers of response and resistance to anti-PD-1, concluding that an optimal biomarker will likely be multifaceted. The second effort involves identifying existing targeted therapies or chemotherapies that may synergize with ICI. In particular, we describe recent efforts to use inhibitors of the PI3K/AKT or RAS/MAPK/ERK pathways in combination with ICI. Third, considering the possibility that targeting the PD-1 axis is not the most promising strategy for TNBC treatment, we describe ongoing efforts to identify novel immunotherapy strategies.

Prognostic value and distribution pattern of tumor infiltrating lymphocytes and their subsets in distant metastases of advanced breast cancer

BACKGROUND

There are significant correlations between the levels of tumor infiltrating lymphocytes (TILs) and the prognosis of primary breast cancer. While little is known about immunological mechanisms in the distant metastasis of advanced breast cancer.

PATIENTS AND METHODS

A total of 106 patients with advanced metastatic breast cancer were enrolled in this study between 2016 and 2022. Hematoxylin and eosin staining and immunohistochemistry were used to assess the densities of stromal TILs (sTILs), intratumoral TILs (iTILs) and invasive marginal TILs (imTILs) and CD4+, CD8+, CD20+, FOXP3+ TILs in the primary tumor and metastasis (bone, lung, liver, and distant lymph node) of advanced breast cancer.

RESULTS

Higher levels of sTILs at metastatic sites were associated with better progression-free survival (PFS), postmetastasis survival (PMS) and overall survival (OS) (p = .026, .001 and .005, respectively). The levels of iTILs were significantly lower than those of sTILs and imTILs in both primary tumor (p< .001, both) and metastasis (p< .001, both). The level of CD4+ T cells was higher than those of CD8+ T cells and CD20+ B cells in both primary tumor (p < .001) and metastasis (p < .001). The levels of sTILs (p=0. 001) and imTILs (p< .001) in the primary tumor were generally higher than those in the metastasis.

CONCLUSION

The levels of TILs and their subsets can predict the survival and prognosis of patients with advanced breast cancer. The distributions of TILs and their subsets are similar between the primary tumor and metastasis. The metastases have a lower degree of lymphocytes infiltration than its corresponding primary tumor.

Molecular Changes in Breast Cancer Induced by Radiation Therapy

PURPOSE

Breast cancer treatments are based on prognostic clinicopathologic features that form the basis for therapeutic guidelines. Although the utilization of these guidelines has decreased breast cancer-associated mortality rates over the past three decades, they are not adequate for individualized therapy. Radiation therapy (RT) is the backbone of breast cancer treatment. Although a highly successful therapeutic modality clinically, from a biological perspective, preclinical studies have shown RT to have the potential to alter tumor cell phenotype, immunogenicity, and the surrounding microenvironment, potentially changing the behavior of cancer cells and resulting in a significant variation in RT response. This review presents the recent advances in revealing the complex molecular changes induced by RT in the treatment of breast cancer and highlights the complexities of translating this information into clinically relevant tools for improved prognostic insights and the revelation of novel approaches for optimizing RT.

METHODS AND MATERIALS

Current literature was reviewed with a focus on recent advances made in the elucidation of tumor-associated radiation-induced molecular changes across molecular, genetic, and proteomic bases. This review was structured with the aim of providing an up-to-date overview over the very broad and complex subject matter of radiation-induced molecular changes and radioresistance, familiarizing the reader with the broader issue at hand.

RESULTS

The subject of radiation-induced molecular changes in breast cancer has been broached from various physiological focal points including that of the immune system, immunogenicity and the abscopal effect, tumor hypoxia, breast cancer classification and subtyping, molecular heterogeneity, and molecular plasticity. It is becoming increasingly apparent that breast cancer clinical subtyping alone does not adequately account for variation in RT response or radioresistance. Multiple components of the tumor microenvironment and immune system, delivered RT dose and fractionation schedules, radiation-induced bystander effects, and intrinsic tumor physiology and heterogeneity all contribute to the resultant RT outcome.

CONCLUSIONS

Despite recent advances and improvements in anticancer therapies, tumor resistance remains a significant challenge. As new analytical techniques and technologies continue to provide crucial insight into the complex molecular mechanisms of breast cancer and its treatment responses, it is becoming more evident that personalized anticancer treatment regimens may be vital in overcoming radioresistance.

Immunotherapy for the treatment of biliary tract cancer: an evolving landscape

Biliary tract cancers (BTCs), consisting of intrahepatic and extrahepatic cholangiocarcinoma and gallbladder cancer, are an aggressive, heterogeneous malignancy. They are most often diagnosed in the locally advanced or metastatic setting, at which point treatment consists of systemic therapy or best supportive care. Our understanding of the tumor microenvironment and the molecular classification has led to the identification of targetable mutations, such as isocitrate dehydrogenase 1 and fibroblast growth factor receptor 2. Despite the identification of these genomic alterations, until recently, little advancement had been made in the first-line setting for advanced BTC. While immunotherapy (IO) has revolutionized the treatment of many malignancies, the use of IO in BTC had yielded limited results prior to TOPAZ-1. In this review, we discuss the systemic therapeutic advances for BTC over the past decade, the rationale for immunotherapy in BTC, prior trials utilizing IO in BTC, and current and emerging immune-based therapeutic options. We further analyze the culmination of these advances, which resulted in the approval of durvalumab with gemcitabine and cisplatin for the first-line treatment of BTC per TOPAZ-1. We also discuss the results of KEYNOTE-966, which similarly reported improved clinical outcomes with the use of pembrolizumab in combination with gemcitabine and cisplatin.

Small molecule inhibitors targeting regulatory T cells for cancer treatment

Regulatory T cells (Tregs) are important controllers of the immune system homeostasis by preventing disproportionate immune responses. In the context of cancer, Tregs contribute to tumor development by suppressing other immune cells in the tumor microenvironment (TME). Infiltration of Tregs in the TME has been associated with poor prognosis in cancer patients. Thus, understanding the mechanisms underlying Treg recruitment and suppressive functions is essential for developing cancer immunotherapies to boost antitumor immune responses. While antibody-based strategies targeting Tregs have shown promise, small molecule inhibitors offer distinct advantages, including oral bioavailability and the ability to penetrate the TME and target intracellular proteins. Here, we provide an overview of small molecule inhibitors that have demonstrated efficacy in modulating Tregs activity in cancer and highlight the need for phenotypic assays to characterize therapeutic compounds.

Combined PARP and WEE1 inhibition triggers anti-tumor immune response in BRCA1/2 wildtype triple-negative breast cancer

Novel therapeutic strategies that can effectively combine with immunotherapies are needed in the treatment of triple-negative breast cancer (TNBC). We demonstrate that combined PARP and WEE1 inhibition are synergistic in controlling tumour growth in BRCA1/2 wild-type TNBC preclinical models. The PARP inhibitor (PARPi) olaparib combined with the WEE1 inhibitor (WEE1i) adavosertib triggered increases in anti-tumour immune responses, including STING pathway activation. Combinations with a STING agonist resulted in further improved durable tumour regression and significant improvements in survival outcomes in murine tumour models of BRCA1/2 wild-type TNBC. In addition, we have identified baseline tumour-infiltrating lymphocyte (TIL) levels as a potential predictive biomarker of response to PARPi, WEE1i and immunotherapies in BRCA1/2 wild-type TNBC.

Immunotherapy in Biliary Tract Cancers: Current Standard-of-Care and Emerging Strategies

Biliary tract cancers (BTCs), comprising intrahepatic, perihilar, and distal cholangiocarcinoma as well as gallbladder adenocarcinoma, continue to be challenging to manage. Conventional chemotherapy regimens for advanced disease are limited in both options and benefits, and more effective perioperative regimens are also needed. Over the last decade, immunotherapy has had a profound impact on the management of many solid tumor types, particularly in using immune checkpoint inhibition to enable a tumor-directed T cell response. Immunotherapy administered on its own has had limited utility in BTCs, in part due to a hostile immune microenvironment and the relative infrequency of biomarker-based tumor-agnostic indications for immunotherapy. However, immunotherapy in conjunction with chemotherapy, molecularly targeted therapies, and/or anti-angiogenic therapies has gained traction, supported by evidence that these agents can impart favorable immunomodulatory effects on the tumor microenvironment. The TOPAZ-1 trial led to the first BTC-specific immunotherapy approval, establishing the combination of durvalumab with gemcitabine and cisplatin as the preferred first-line treatment for advanced or metastatic disease. Recently, the KEYNOTE-966 trial showed positive results for the combination of pembrolizumab with gemcitabine and cisplatin in the same setting, adding further evidence for the addition of immune checkpoint inhibition to the standard chemotherapy backbone. Meanwhile, advances in the molecular profiling of BTCs has contributed to the recent proliferation of molecularly targeted therapeutics for the subset of BTCs harboring alterations in IDH1, FGFR2, MAP kinase signaling, HER2, and beyond, and there has been great interest in investigating combinations of these agents with immunotherapy. Emerging immunotherapy strategies beyond immune checkpoint inhibition are also being studied in BTCs, and these include immunostimulatory receptor agonists, Wnt signaling modulators, adoptive cell therapy, and cancer vaccines. A large number of trials are underway to explore promising new combinations and immune-targeted strategies, offering opportunities to expand the role of immunotherapy in BTC management in the near future.

Targeting Angiogenesis in the Era of Biliary Tract Cancer Immunotherapy: Biological Rationale, Clinical Implications, and Future Research Avenues

Although biliary tract cancers are traditionally considered rare in Western countries, their incidence and mortality rates are rising worldwide. A better knowledge of the genomic landscape of these tumor types has broadened the number of molecular targeted therapies, including angiogenesis inhibitors. The role of immune checkpoint inhibitors (ICIs) could potentially change the first-line therapeutic approach, but monotherapy with ICIs has shown disappointing results in CCA. Several clinical trials are evaluating combination strategies that include immunotherapy together with other anticancer agents with a synergistic activity. The tumor microenvironment (TME) composition plays a pivotal role in the prognosis of BTC patients. The accumulation of immunosuppressive cell types, such as tumor-associated macrophages (TAMs) and regulatory T-cells, together with the poor infiltration of cytotoxic CD8+ T-cells, is known to predispose to a poor prognosis owing to the establishment of resistance mechanisms. Likewise, angiogenesis is recognized as a major player in modulating the TME in an immunosuppressive manner. This is the mechanistic rationale for combination treatment schemes blocking both immunity and angiogenesis. In this scenario, this review aims to provide an overview of the most recent completed or ongoing clinical trials combining immunotherapy and angiogenesis inhibitors with/without a chemotherapy backbone.

Empowering the Potential of CAR-T Cell Immunotherapies by Epigenetic Reprogramming

T-cell-based, personalized immunotherapy can nowadays be considered the mainstream treatment for certain blood cancers, with a high potential for expanding indications. Chimeric antigen receptor T cells (CAR-Ts), an ex vivo genetically modified T-cell therapy product redirected to target an antigen of interest, have achieved unforeseen successes in patients with B-cell hematologic malignancies. Frequently, however, CAR-T cell therapies fail to provide durable responses while they have met with only limited success in treating solid cancers because unique, unaddressed challenges, including poor persistence, impaired trafficking to the tumor, and site penetration through a hostile microenvironment, impede their efficacy. Increasing evidence suggests that CAR-Ts' in vivo performance is associated with T-cell intrinsic features that may be epigenetically altered or dysregulated. In this review, we focus on the impact of epigenetic regulation on T-cell differentiation, exhaustion, and tumor infiltration and discuss how epigenetic reprogramming may enhance CAR-Ts' memory phenotype, trafficking, and fitness, contributing to the development of a new generation of potent CAR-T immunotherapies.

At the crossroads of immunotherapy for oncogene-addicted subsets of NSCLC

Non-small-cell lung cancer (NSCLC) has become a paradigm of precision medicine, with the discovery of numerous disease subtypes defined by specific oncogenic driver mutations leading to the development of a range of molecularly targeted therapies. Over the past decade, rapid progress has also been made in the development of immune-checkpoint inhibitors (ICIs), especially antagonistic antibodies targeting the PD-L1-PD-1 axis, for the treatment of NSCLC. Although many of the major oncogenic drivers of NSCLC are associated with intrinsic resistance to ICIs, patients with certain oncogene-driven subtypes of the disease that are highly responsive to specific targeted therapies might also derive benefit from immunotherapy. However, the development of effective immunotherapy approaches for oncogene-addicted NSCLC has been challenged by a lack of predictive biomarkers for patient selection and limited knowledge of how ICIs and oncogene-directed targeted therapies should be combined. Therefore, whether ICIs alone or with chemotherapy or even in combination with molecularly targeted agents would offer comparable benefit in the context of selected oncogenic driver alterations to that observed in the general unselected NSCLC population remains an open question. In this Review, we discuss the effects of oncogenic driver mutations on the efficacy of ICIs and the immune tumour microenvironment as well as the potential vulnerabilities that could be exploited to overcome the challenges of immunotherapy for oncogene-addicted NSCLC.

Altered microRNA expression profile is linked to T-cell exhaustion-related pathways in pediatric patients with acute lymphoblastic leukemia

BACKGROUND

Although the phenotype and functions of exhausted T cells in several cancers have been identified, the involved molecular mechanisms remain to be further elucidated. In this regard, we have recently reported that the immunoregulatory cells, including myeloid-derived suppressor cells (MDSCs) and regulatory T cells (T_regs), share common dysregulated miRNAs that target specific immunosuppressive pathways in patients with in acute lymphoblastic leukemia (ALL).

AIM

In this study, we aimed to further explore whether similar dysregulation in miRNA expression is linked to T cell exhaustion and dysfunctionality in B cell ALL patients.

METHODS

Peripheral blood samples from pediatric patients with ALL were recruited before and after induction chemotherapy as well as from healthy donors. Affymetrix microarray platform was used for miRNA profiling, and qRT-PCR was used to validate the expression of certain miRNAs that are related to T cell exhaustion. Bioinformatics analysis was performed to explore whether the dysregulated miRNAs were linked to T-cell exhaustion related pathways.

RESULTS

A total of 516 miRNAs were dysregulated in ALL patients as compared to the healthy donor. Furthermore, among the total analyzed miRNAs, 10 were found to be linked to the key genes implicated in three exhaustion-related pathways; TGF-β, FOXO, and MAPK, as revealed by miR-pathway analysis. Moreover, qRT-PCR analysis showed similar expression pattern to those obtained by microarray analysis.

CONCLUSION

Our pilot study suggests the implication of certain miRNAs in T cell exhaustion pathways via targeting the specific key genes in those pathways.

Mechanisms driving the immunoregulatory function of cancer cells

Tumours display an astonishing variation in the spatial distribution, composition and activation state of immune cells, which impacts their progression and response to immunotherapy. Shedding light on the mechanisms that govern the diversity and function of immune cells in the tumour microenvironment will pave the way for the development of more tailored immunomodulatory strategies for the benefit of patients with cancer. Cancer cells, by virtue of their paracrine and juxtacrine communication mechanisms, are key contributors to intertumour heterogeneity in immune contextures. In this Review, we discuss how cancer cell-intrinsic features, including (epi)genetic aberrations, signalling pathway deregulation and altered metabolism, play a key role in orchestrating the composition and functional state of the immune landscape, and influence the therapeutic benefit of immunomodulatory strategies. Moreover, we highlight how targeting cancer cell-intrinsic parameters or their downstream immunoregulatory pathways is a viable strategy to manipulate the tumour immune milieu in favour of antitumour immunity.

Association of clinical outcomes and the predictive value of T lymphocyte subsets within colorectal cancer patients

Introduction

Tumor immunity is a hot topic in tumor research today, and human immunity is closely related to tumor progression. T lymphocyte is an important component of human immune system, and the changes in their subsets may influence the progression of colorectal cancer (CRC) to some extent. This clinical study systematically describes and analyzes the association of CD4⁺ and CD8⁺ T-lymphocyte content and CD4⁺/CD8⁺ T-lymphocyte ratio with CRC differentiation, clinical pathological stage, Ki67 expression, T-stage, N-stage, carcinoembryonic antigen (CEA) content, nerve and vascular infiltration, and other clinical features, as well as preoperative and postoperative trends. Furthermore, a predictive model is constructed to evaluate the predictive value of T-lymphocyte subsets for CRC clinical features.

Methods

Strict inclusion and exclusion criterion were formulated to screen patients, preoperative and postoperative flow cytometry and postoperative pathology reports from standard laparoscopic surgery were assessed. PASS and SPSS software, R packages were invoked to calculate and analyze.

Results

We found that a high CD4⁺ T-lymphocyte content in peripheral blood and a high CD4⁺/CD8⁺ ratio were associated with better tumor differentiation, an earlier clinical pathological stage, lower Ki67 expression, shallower tumor infiltration, a smaller number of lymph node metastases, a lower CEA content, and a lower likelihood of nerve or vascular infiltration (P < 0.05). However, a high CD8⁺ T-lymphocyte content indicated an unpromising clinical profile. After effective surgical treatment, the CD4⁺ T-lymphocyte content and CD4⁺/CD8⁺ ratio increased significantly (P < 0.05), while the CD8⁺ T-lymphocyte content decreased significantly (P < 0.05). Further, we comprehensively compared the merits of CD4⁺ T-lymphocyte content, CD8⁺ T-lymphocyte content, and CD4⁺/CD8⁺ ratio in predicting the clinical features of CRC. We then combined the CD4⁺ and CD8⁺ T-lymphocyte content to build models and predict major clinical characteristics. We compared these models with the CD4⁺/CD8⁺ ratio to explore their advantages and disadvantages in predicting the clinical features of CRC.

Discussion

Our results provide a theoretical basis for the future screening of effective markers in reflecting and predicting the progression of CRC. Changes in T lymphocyte subsets affect the progression of CRC to a certain extent, while their changes also reflect variations in the human immune system.

Changes in the Immune Cell Repertoire for the Treatment of Malignant Melanoma

Immune checkpoint inhibitors (ICIs) have been used for the treatment of various types of cancers, including malignant melanoma. Mechanistic exploration of tumor immune responses is essential to improve the therapeutic efficacy of ICIs. Since tumor immune responses are based on antigen-specific immune responses, investigators have focused on T cell receptors (TCRs) and have analyzed changes in the TCR repertoire. The proliferation of T cell clones against tumor antigens is detected in patients who respond to treatment with ICIs. The proliferation of these T cell clones is observed within tumors as well as in the peripheral blood. Clonal proliferation has been detected not only in CD8-positive T cells but also in CD4-positive T cells, resident memory T cells, and B cells. Moreover, changes in the repertoire at an early stage of treatment seem to be useful for predicting the therapeutic efficacy of ICIs. Further analyses of the repertoire of immune cells are desirable to improve and predict the therapeutic efficacy of ICIs.

Immune Checkpoint Inhibitors and RAS-ERK Pathway-Targeted Drugs as Combined Therapy for the Treatment of Melanoma

Metastatic melanoma is a highly immunogenic tumor with very poor survival rates due to immune system escape-mechanisms. Immune checkpoint inhibitors (ICIs) targeting the cytotoxic T-lymphocyte-associated protein 4 (CTLA4) and the programmed death-1 (PD1) receptors, are being used to impede immune evasion. This immunotherapy entails an increment in the overall survival rates. However, melanoma cells respond with evasive molecular mechanisms. ERK cascade inhibitors are also used in metastatic melanoma treatment, with the RAF activity blockade being the main therapeutic approach for such purpose, and in combination with MEK inhibitors improves many parameters of clinical efficacy. Despite their efficacy in inhibiting ERK signaling, the rewiring of the melanoma cell-signaling results in disease relapse, constituting the reinstatement of ERK activation, which is a common cause of some resistance mechanisms. Recent studies revealed that the combination of RAS-ERK pathway inhibitors and ICI therapy present promising advantages for metastatic melanoma treatment. Here, we present a recompilation of the combined therapies clinically evaluated in patients.

Combined MEK/PD-L1 Inhibition Alters Peripheral Cytokines and Lymphocyte Populations Correlating with Improved Clinical Outcomes in Advanced Biliary Tract Cancer

PURPOSE

Biliary tract cancers (BTC) are aggressive malignancies refractory to chemotherapy and immunotherapy. MEK inhibition (MEKi)-based regimens may have utility in this disease when combined with PD-L1 blockade. We hypothesize that dual MEK/PD-L1 inhibition alters circulating soluble and cellular immune mediators to improve clinical outcomes in patients with advanced BTC.

EXPERIMENTAL DESIGN

We examined immune features in peripheral blood from 77 patients with advanced BTC enrolled in a phase II clinical trial investigating atezolizumab with or without cobimetinib. Plasma and peripheral blood mononuclear cells (PBMC) were isolated from whole blood to evaluate soluble factors and immune cell populations. Baseline blood samples were additionally compared with healthy donors to identify immune signatures unique to BTC.

RESULTS

At baseline, the soluble factors platelet-derived growth factor B (PDGF)-BB, placental growth factor (PlGF)-1, IL5, and IL17A were elevated in patients with BTC compared with healthy adult donors, and higher baseline frequencies of CD8+BTLA+ T cells correlated with better overall survival (OS) in this trial. There were also significant treatment-related alterations in several factors, including decreased PDGF-BB following combination treatment, that correlated with improved OS and progression-free survival (PFS). Higher baseline levels of IL23 and RANTES corresponded to improved clinical outcomes following combination treatment. Dual MEK/PD-L1 inhibition increased populations of CD4+TIM3+ and decreased CD8+VISTA+ T cells, correlating with worse OS and better PFS, respectively.

CONCLUSIONS

This work represents a comprehensive analysis of peripheral immune features in patients with BTC and systemic responses to dual MEK/PD-L1 inhibition. These data support further investigation to understand how MEKi combines with immunotherapeutic approaches to improve clinical outcomes for patients with advanced BTC.

Intermittent MEK inhibition for the treatment of metastatic uveal melanoma

Introduction

Uveal melanoma (UM) is associated with poor outcomes in the metastatic setting and harbors activating mutations resulting in upregulation of MAPK signaling in almost all cases. The efficacy of selumetinib, an oral allosteric inhibitor of MEK1/2, was limited when administered at a continual dosing schedule of 75 mg BID. Preclinical studies demonstrate that intermittent MEK inhibition reduces compensatory pathway activation and promotes T cell activation. We hypothesized that intermittent dosing of selumetinib would reduce toxicity, allow for the administration of increased doses, and achieve more complete pathway inhibition, thus resulting in improved antitumor activity.

Methods

We conducted a phase Ib trial of selumetinib using an intermittent dosing schedule in patients with metastatic UM. The primary objective was to estimate the maximum tolerated dose (MTD) and assess safety and tolerability. Secondary objectives included assessment of the overall response rate (RR), progression-free survival (PFS) and overall survival (OS). Tumor biopsies were collected at baseline, on day 3 (on treatment), and between days 11-14 (off treatment) from 9 patients for pharmacodynamic (PD) assessments.

Results

29 patients were enrolled and received at least one dose of selumetinib across 4 dose levels (DL; DL1: 100 mg BID; DL2: 125 mg BID; DL3: 150 mg BID; DL4: 175 mg BID). All patients experienced a treatment-related adverse event (TRAE), with 5/29 (17%) developing a grade 3 or higher TRAE. Five dose limiting toxicities (DLT) were observed: 2/20 in DL2, 2/5 in DL3, 1/1 in DL4. The estimated MTD was 150 mg BID (DL3), with an estimated probability of toxicity of 29% (90% probability interval 16%-44%). No responses were observed; 11/29 patients achieved a best response of stable disease (SD). The median PFS and OS were 1.8 months (95% CI 1.7, 4.5) and 7.1 months (95% CI 5.3, 11.5). PD analysis demonstrated at least partial pathway inhibition in all samples at day 3, with reactivation between days 11-14 in 7 of those cases.

Conclusions

We identified 150 mg BID as the MTD of intermittent selumetinib, representing a 100% increase over the continuous dose MTD (75 mg BID). However, no significant clinical efficacy was observed using this dosing schedule.

The implications from the interplay of neoadjuvant chemoradiotherapy and the immune microenvironment in rectal cancer

Neoadjuvant chemoradiotherapy (nCRT) is recommended for the treatment of locally advanced rectal cancer. Even though the combination of nCRT and immune checkpoint inhibitors (ICIs) has received much attention, the specific combination modes and dose fractions in radiotherapy (RT) are still indistinct. This review focuses on the immunological mechanism involved in nCRT, the clinical efficacy, the immunological effect of different combined strategies, concurrent or sequential nCRT plus ICIs, long-course RT and short-course RT. This review discusses the impact of nCRT on tumor immunity and summarizes the availability of different dose fractions in RT and distinct combined strategies, aiming at providing clues for optimal neoadjuvant therapy options that maximize efficacy and minimize side effects.

Small-Molecule PROTACs for Cancer Immunotherapy

Unsatisfactory physicochemical properties of macromolecular drugs seriously hinder their application in tumor immunotherapy. However, these problems can be effectively solved by small-molecule compounds. In the promising field of small-molecule drug development, proteolysis targeting chimera (PROTAC) offers a novel mode of action in the interactions between small molecules and therapeutic targets (mainly proteins). This revolutionary technology has shown considerable impact on several proteins related to tumor survival but is rarely exploited in proteins associated with immuno-oncology up until now. This review attempts to comprehensively summarize the well-studied and less-developed immunological targets available for PROTAC technology, as well as some targets to be explored, aiming to provide more options and opportunities for the development of small-molecule-based tumor immunotherapy. In addition, some novel directions that can magnify and broaden the protein degradation efficiency are mentioned to improve PROTAC design in the future.

The expanding role for small molecules in immuno-oncology

The advent of immune checkpoint inhibition (ICI) using antibodies against PD1 and its ligand PDL1 has prompted substantial efforts to develop complementary drugs. Although many of these are antibodies directed against additional checkpoint proteins, there is an increasing interest in small-molecule immuno-oncology drugs that address intracellular pathways, some of which have recently entered clinical trials. In parallel, small molecules that target pro-tumorigenic pathways in cancer cells and the tumour microenvironment have been found to have immunostimulatory effects that synergize with the action of ICI antibodies, leading to the approval of an increasing number of regimens that combine such drugs. Combinations with small molecules targeting cancer metabolism, cytokine/chemokine and innate immune pathways, and T cell checkpoints are now under investigation. This Review discusses the recent milestones and hurdles encountered in this area of drug development, as well as our views on the best path forward.

Oncogenic signaling pathway-related long non-coding RNAs for predicting prognosis and immunotherapy response in breast cancer

Background

The clinical outcomes of breast cancer (BC) are unpredictable due to the high level of heterogeneity and complex immune status of the tumor microenvironment (TME). When set up, multiple long non-coding RNA (lncRNA) signatures tended to be employed to appraise the prognosis of BC. Nevertheless, predicting immunotherapy responses in BC is still essential. LncRNAs play pivotal roles in cancer development through diverse oncogenic signal pathways. Hence, we attempted to construct an oncogenic signal pathway–based lncRNA signature for forecasting prognosis and immunotherapy response by providing reliable signatures.

Methods

We preliminarily retrieved RNA sequencing (RNA-seq) data from The Cancer Genome Atlas (TCGA) database and extracted lncRNA profiles by matching them with GENCODE. Following this, Gene Set Variation Analysis (GSVA) was used to identify the lncRNAs closely associated with 10 oncogenic signaling pathways from the TCGA-BRCA (breast-invasive carcinoma) cohort and was further screened by the least absolute shrinkage and selection operator Cox regression model. Next, an lncRNA signature (OncoSig) was established through the expression level of the final 29 selected lncRNAs. To examine survival differences in the stratification described by the OncoSig, the Kaplan–Meier (KM) survival curve with the log-rank test was operated on four independent cohorts (n = 936). Subsequently, multiple Cox regression was used to investigate the independence of the OncoSig as a prognostic factor. With the concordance index (C-index), the time-dependent receiver operating characteristic was employed to assess the performance of the OncoSig compared to other publicly available lncRNA signatures for BC. In addition, biological differences between the high- and low-risk groups, as portrayed by the OncoSig, were analyzed on the basis of statistical tests. Immune cell infiltration was investigated using gene set enrichment analysis (GSEA) and deconvolution tools (including CIBERSORT and ESTIMATE). The combined effect of the Oncosig and immune checkpoint genes on prognosis and immunotherapy was elucidated through the KM survival curve. Ultimately, a pan-cancer analysis was conducted to attest to the prevalence of the OncoSig.

Results

The OncoSig score stratified BC patients into high- and low-risk groups, where the latter manifested a significantly higher survival rate and immune cell infiltration when compared to the former. A multivariate analysis suggested that OncoSig is an independent prognosis predictor for BC patients. In addition, compared to the other four publicly available lncRNA signatures, OncoSig exhibited superior predictive performance (AUC = 0.787, mean C-index = 0.714). The analyses of the OncoSig and immune checkpoint genes clarified that a lower OncoSig score meant significantly longer survival and improved response to immunotherapy. In addition to BC, a high OncoSig score in several other cancers was negatively correlated with survival and immune cell infiltration.

Conclusions

Our study established a trustworthy and discriminable prognostic signature for BC patients with similar clinical profiles, thus providing a new perspective in the evaluation of immunotherapy responses. More importantly, this finding can be generalized to be applicable to the vast majority of human cancers.

Icaritin and intratumoral injection of CpG treatment synergistically promote T cell infiltration and antitumor immune response in mice

The development of combination therapy that can modulate the tumor immunosuppressive microenvironment is highly desirable for cancer immunotherapy. Icaritin (ICT), a hydrolytic product of icariin from genus Epimedium, has been used as an anti-cancer immunoregulatory agent for many types of cancers. Herein, we design a novel therapeutic strategy for mice melanoma that combines systemic administration of icaritin with intratumoral injection of unmethylated cytosine-guanine oligodeoxynucleotide (CpG). Icaritin induces tumor cell apoptosis and increases tumor immunogenicity. The combination of icaritin with CpG synergistically suppresses tumor growth and significantly prolonged survival time of B16F10 melanoma bearing mice. importantly, the anti-tumor effects of this combination strategy are associated with the reversing of immunosuppressive microenvironment through increased recruitment of functional DCs and tumor-associated macrophages (TAM) in tumors, leading to the infiltration of cytotoxic CD8⁺ T cells expressing elevated levels of IFN-γ and TNF-α. Furthermore, the combination of icaritin with CpG augments the anti-tumor immune response to anti-PD-1/CTLA-4 immune checkpoint blockade treatment. These results support the combination of icaritin with CpG as a novel strategy to elicit effective T cell-mediated antitumor immune response.

Onco-immunomodulatory properties of pharmacological interference with RAS-RAF-MEK-ERK pathway hyperactivation

Hyperactivation of the RAS-RAF-MEK-ERK cascade - a mitogen-activated protein kinase pathway – has a well-known association with oncogenesis of leading tumor entities, including non-small cell lung cancer, colorectal carcinoma, pancreatic ductal adenocarcinoma, and malignant melanoma. Increasing evidence shows that genetic alterations leading to RAS-RAF-MEK-ERK pathway hyperactivation mediate contact- and soluble-dependent crosstalk between tumor, tumor microenvironment (TME) and the immune system resulting in immune escape mechanisms and establishment of a tumor-sustaining environment. Consequently, pharmacological interruption of this pathway not only leads to tumor-cell intrinsic disruptive effects but also modification of the TME and anti-tumor immunomodulation. At the same time, the importance of ERK signaling in immune cell physiology and potentiation of anti-tumor immune responses through ERK signaling inhibition within immune cell subsets has received growing appreciation. Specifically, a strong case was made for targeted MEK inhibition due to promising associated immune cell intrinsic modulatory effects. However, the successful transition of therapeutic agents interrupting RAS-RAF-MEK-ERK hyperactivation is still being hampered by significant limitations regarding durable efficacy, therapy resistance and toxicity. We here collate and summarize the multifaceted role of RAS-RAF-MEK-ERK signaling in physiology and oncoimmunology and outline the rationale and concepts for exploitation of immunomodulatory properties of RAS-RAF-MEK-ERK inhibition while accentuating the role of MEK inhibition in combinatorial and intermittent anticancer therapy. Furthermore, we point out the extensive scientific efforts dedicated to overcoming the challenges encountered during the clinical transition of various therapeutic agents in the search for the most effective and safe patient- and tumor-tailored treatment approach.

From Immunohistochemistry to New Digital Ecosystems: A State-of-the-Art Biomarker Review for Precision Breast Cancer Medicine

Simple Summary

In this state-of-the-art breast biomarker review, we have tried to imagine and illustrate future, emerging digital breast cancer ecosystems which allow for greater incorporation of traditional immunohistochemical and molecular biomarkers, WSI, and radiomic features.

Abstract

Breast cancers represent complex ecosystem-like networks of malignant cells and their associated microenvironment. Estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2) are biomarkers ubiquitous to clinical practice in evaluating prognosis and predicting response to therapy. Recent feats in breast cancer have led to a new digital era, and advanced clinical trials have resulted in a growing number of personalized therapies with corresponding biomarkers. In this state-of-the-art review, we included the latest 10-year updated recommendations for ER, PR, and HER2, along with the most salient information on tumor-infiltrating lymphocytes (TILs), Ki-67, PD-L1, and several prognostic/predictive biomarkers at genomic, transcriptomic, and proteomic levels recently developed for selection and optimization of breast cancer treatment. Looking forward, the multi-omic landscape of the tumor ecosystem could be integrated with computational findings from whole slide images and radiomics in predictive machine learning (ML) models. These are new digital ecosystems on the road to precision breast cancer medicine.

Combination of OX40 Co-Stimulation, Radiotherapy, and PD-1 Inhibition in a Syngeneic Murine Triple-Negative Breast Cancer Model

Simple Summary

This experimental study was designed in order to investigate the efficacy of the triple combination of radiation (SBRT), PD-1 blockade, and OX40 co-stimulation in a syngeneic murine model using ‘immunologically cold’ triple-negative breast cancer cells. SBRT can induce immunogenic tumor cell deaths and act as an in situ vaccine while OX40 signaling has been shown to improve anticancer immunity combined with PD-1 inhibition via multiple preclinical studies. In our study, triple combination therapy significantly improved primary/abscopal tumor control and reduced lung metastases compared to single or dual therapies. This was found to be through an increased ratio of CD8+ T cells to regulatory T cells and a reduced proportion of exhausted T cells in the tumor microenvironment.

Abstract

Immune checkpoint inhibitors have been successful in a wide range of tumor types but still have limited efficacy in immunologically cold tumors, such as breast cancers. We hypothesized that the combination of agonistic anti-OX40 (α-OX40) co-stimulation, PD-1 blockade, and radiotherapy would improve the therapeutic efficacy of the immune checkpoint blockade in a syngeneic murine triple-negative breast cancer model. Murine triple-negative breast cancer cells (4T1) were grown in immune-competent BALB/c mice, and tumors were irradiated with 24 Gy in three fractions. PD-1 blockade and α-OX40 were administered five times every other day. Flow cytometric analyses and immunohistochemistry were used to monitor subsequent changes in the immune cell repertoire. The combination of α-OX40, radiotherapy, and PD-1 blockade significantly improved primary tumor control, abscopal effects, and long-term survival beyond 2 months (60%). In the tumor microenvironment, the ratio of CD8+ T cells to CD4 + FOXP3+ regulatory T cells was significantly elevated and exhausted CD8+ T cells (PD-1+, CTLA-4+, TIM-3+, or LAG-3+ cells) were significantly reduced in the triple combination group. Systemically, α-OX40 co-stimulation and radiation significantly increased the CD103+ dendritic cell response in the spleen and plasma IFN-γ, respectively. Together, our results suggest that the combination of α-OX40 co-stimulation and radiation is a viable approach to overcome therapeutic resistance to PD-1 blockade in immunologically cold tumors, such as triple-negative breast cancer.

Combination targeted and immune therapy in the treatment of advanced melanoma: a valid treatment option for patients?

Melanomas harboring an activating BRAFV600 mutation account for 50% of all advanced melanomas. The approval of BRAF-targeted therapy revolutionized treatment of these patients with achievement of impressive responses. However, development of resistance to these drugs is a significant problem, and as such, duration of response remains low, with median progression free survival of around 11–15 months. Immune checkpoint blockers exploit the immune system to eradicate cancer and can produce durable disease control that results in long-term, treatment-free survival in some patients. These drugs have shown very impressive survival in patients with BRAF-mutated melanoma. Thus, there is a need to continue to utilize emerging data to achieve long-term disease control for patients with advanced melanoma. Combining targeted therapy with immune therapy may be one possible way to achieve this goal. In this review, the mechanisms of action of these two pathways, including the mechanistic basis of this combination, are summarized, along with results of completed and ongoing trials in triple therapy.

B7 homolog 3 induces lung metastasis of breast cancer through Raf/MEK/ERK axis

PURPOSE

The essential action of B7 homolog 3 (B7-H3) in different diseases and cancers has been documented. We here focused on its role in breast cancer through the Raf/MEK/ERK axis regarding lung metastasis.

METHODS

Expression pattern of B7-H3 was determined in breast cancer tissues and cells with its correlation with prognosis analyzed. Then, through transfection of lentivirus vector expressing B7-H3-shRNA, overexpression vector of B7-H3 (B7-H3-LV), U0126 (small molecule inhibitor of MEK), or PD98059 (small molecule inhibitor of ERK), the in vitro and in vivo effects of B7-H3 in breast cancer cell biological processes, and lung metastasis were analyzed in relation to the Raf/MEK/ERK axis.

RESULTS

We discovered elevated B7-H3 in breast cancer and its elevation associated with poor prognosis. B7-H3 promoted the malignant properties of breast cancer cells, accompanied with increased N-cadherin and vimentin and reduced E-cadherin. Additionally, overexpression of B7-H3 accelerated the lung metastasis in breast cancer in vivo. All the above promoting action of B7-H3 was achieved through activation of the Raf/MEK/ERK signaling pathway.

CONCLUSION

Taken together, B7-H3 can promote lung metastasis in breast cancer through activation of the Raf/MEK/ERK axis.

Targeting oncogene and non-oncogene addiction to inflame the tumour microenvironment

Immune checkpoint inhibitors (ICIs) have revolutionized the clinical management of multiple tumours. However, only a few patients respond to ICIs, which has generated considerable interest in the identification of resistance mechanisms. One such mechanism reflects the ability of various oncogenic pathways, as well as stress response pathways required for the survival of transformed cells (a situation commonly referred to as 'non-oncogene addiction'), to support tumour progression not only by providing malignant cells with survival and/or proliferation advantages, but also by establishing immunologically 'cold' tumour microenvironments (TMEs). Thus, both oncogene and non-oncogene addiction stand out as promising targets to robustly inflame the TME and potentially enable superior responses to ICIs.

Targeting LAG3/GAL-3 to overcome immunosuppression and enhance anti-tumor immune responses in multiple myeloma

Immune profiling in patients with monoclonal gammopathy of undetermined significance (MGUS), smoldering multiple myeloma (SMM), and multiple myeloma (MM) provides the framework for developing novel immunotherapeutic strategies. Here, we demonstrate decreased CD4⁺ Th cells, increased Treg and G-type MDSC, and upregulation of immune checkpoints on effector/regulatory and CD138⁺ cells in MM patients, compared MGUS/SMM patients or healthy individuals. Among the checkpoints profiled, LAG3 was most highly expressed on proliferating CD4⁺ Th and CD8⁺ Tc cells in MM patients BMMC and PBMC. Treatment with antibody targeting LAG3 significantly enhanced T cells proliferation and activities against MM. XBP1/CD138/CS1-specific CTL generated in vitro displayed anti-MM activity, which was further enhanced following anti-LAG3 treatment, within the antigen-specific memory T cells. Treg and G-type MDSC weakly express LAG3 and were minimally impacted by anti-LAG3. CD138⁺ MM cells express GAL-3, a ligand for LAG3, and anti-GAL-3 treatment increased MM-specific responses, as observed for anti-LAG3. Finally, we demonstrate checkpoint inhibitor treatment evokes non-targeted checkpoints as a cause of resistance and propose combination therapeutic strategies to overcome this resistance. These studies identify and validate blockade of LAG3/GAL-3, alone or in combination with immune strategies including XBP1/CD138/CS1 multipeptide vaccination, to enhance anti-tumor responses and improve patient outcome in MM.

Multicenter randomized phase II trial of atezolizumab with or without cobimetinib in biliary tract cancers

BACKGROUNDMEK inhibitors have limited activity in biliary tract cancers (BTCs) as monotherapy but are hypothesized to enhance responses to programmed death ligand 1 (PD-L1) inhibition.METHODSThis open-label phase II study randomized patients with BTC to atezolizumab (anti-PD-L1) as monotherapy or in combination with cobimetinib (MEK inhibitor). Eligible patients had unresectable BTC with 1 to 2 lines of prior therapy in the metastatic setting, measurable disease, and Eastern Cooperative Oncology Group (ECOG) performance status less than or equal to 1. The primary endpoint was progression-free survival (PFS).RESULTSSeventy-seven patients were randomized and received study therapy. The trial met its primary endpoint, with a median PFS of 3.65 months in the combination arm versus 1.87 months in the monotherapy arm (HR 0.58, 90% CI 0.35-0.93, 1-tail P = 0.027). One patient in the combination arm (3.3%) and 1 patient in the monotherapy arm (2.8%) had a partial response. Combination therapy was associated with more rash, gastrointestinal events, CPK elevations, and thrombocytopenia. Exploratory analysis of tumor biopsies revealed enhanced expression of antigen processing and presentation genes and an increase in CD8/FoxP3 ratios with combination treatment. Patients with higher baseline or lower fold changes in expression of certain inhibitory ligands (LAG3, BTLA, VISTA) on circulating T cells had evidence of greater clinical benefit from the combination.CONCLUSIONThe combination of atezolizumab plus cobimetinib prolonged PFS as compared with atezolizumab monotherapy, but the low response rate in both arms highlights the immune-resistant nature of BTCs.TRIAL REGISTRATIONClinicalTrials.gov NCT03201458.FUNDINGNational Cancer Institute (NCI) Experimental Therapeutics Clinical Trials Network (ETCTN); F. Hoffmann-La Roche, Ltd.; NCI, NIH (R01 CA228414-01 and UM1CA186691); NCI's Specialized Program of Research Excellence (SPORE) in Gastrointestinal Cancers (P50 CA062924); NIH Center Core Grant (P30 CA006973); and the Passano Foundation.

The tale of TILs in breast cancer: A report from The International Immuno-Oncology Biomarker Working Group

The advent of immune-checkpoint inhibitors (ICI) in modern oncology has significantly improved survival in several cancer settings. A subgroup of women with breast cancer (BC) has immunogenic infiltration of lymphocytes with expression of programmed death-ligand 1 (PD-L1). These patients may potentially benefit from ICI targeting the programmed death 1 (PD-1)/PD-L1 signaling axis. The use of tumor-infiltrating lymphocytes (TILs) as predictive and prognostic biomarkers has been under intense examination. Emerging data suggest that TILs are associated with response to both cytotoxic treatments and immunotherapy, particularly for patients with triple-negative BC. In this review from The International Immuno-Oncology Biomarker Working Group, we discuss (a) the biological understanding of TILs, (b) their analytical and clinical validity and efforts toward the clinical utility in BC, and (c) the current status of PD-L1 and TIL testing across different continents, including experiences from low-to-middle-income countries, incorporating also the view of a patient advocate. This information will help set the stage for future approaches to optimize the understanding and clinical utilization of TIL analysis in patients with BC.

Sustained compensatory p38 MAPK signaling following treatment with MAPK inhibitors induces the immunosuppressive protein CD73 in cancer: combined targeting could improve outcomes

RAS-MAPK signaling promotes immune evasion and cancer cell survival, and MAPK inhibitors (MAPKis) are frequently used as cancer therapies. Despite progress elucidating the direct effects of MAPKi on immune cells, their indirect effect on the tumor microenvironment (TME) through changes in tumor cells remains incompletely understood. Here, we present evidence of a rapid compensatory response to MAPKi that is driven by sustained p38 MAPK signaling and by which cancer cells can upregulate the immunosuppressive protein CD73 to reduce the antitumor immune response. This compensatory response also results in decreased sensitivity toward MAPKi, and, accordingly, combining anti-CD73 antibodies and MAPKi significantly enhances the antitumor effect compared to single-agent treatment in vivo. Combining MAPKi and anti-CD73 was accompanied by significant alterations in intratumor immune cell composition, supporting the effect of MAPKi-induced CD73 expression on the TME. We show that high CD73 expression significantly correlates with worse outcome in MAPKi-treated colorectal cancer patients, highlighting the potential clinical importance of increased CD73 expression following MAPKi treatment. Our findings may explain the diminished effect of MAPKi in cancer patients and provides further rationale for combined anti-CD73 and MAPKi treatment.

Therapeutic Associations Comprising Anti-PD-1/PD-L1 in Breast Cancer: Clinical Challenges and Perspectives

Despite a few cases of long-responder patients, immunotherapy with anti-PD-(L)1 has so far proved rather disappointing in monotherapy in metastatic breast cancer, prompting the use of synergistic therapeutic combinations incorporating immunotherapy by immune-checkpoint inhibitors. In addition, a better understanding of both the mechanisms of sensitivity and resistance to immunotherapy, as well as the immunological effects of the usual treatments for breast cancer, make it possible to rationally consider this type of therapeutic combination. For several years, certain treatments, commonly used to treat patients with breast cancer, have shown that in addition to their direct cytotoxic effects, they may have an impact on the tumor immune microenvironment, by increasing the antigenicity and/or immunogenicity of a "cold" tumor, targeting the immunosuppressive microenvironment or counteracting the immune-exclusion profile. This review focuses on preclinical immunologic synergic mechanisms of various standard therapeutic approaches with anti-PD-(L)1, and discusses the potential clinical use of anti-PD-1/L1 combinations in metastatic or early breast cancer.

Directing T-Cell Immune Responses for Cancer Vaccination and Immunotherapy

Cancer vaccination and immunotherapy revolutionised the treatment of cancer, a result of decades of research into the immune system in health and disease. However, despite recent breakthroughs in treating otherwise terminal cancer, only a minority of patients respond to cancer immunotherapy and some cancers are largely refractive to immunotherapy treatment. This is due to numerous issues intrinsic to the tumour, its microenvironment, or the immune system. CD4+ and CD8+ αβ T-cells emerged as the primary effector cells of the anti-tumour immune response but their function in cancer patients is often compromised. This review details the mechanisms by which T-cell responses are hindered in the setting of cancer and refractive to immunotherapy, and details many of the approaches under investigation to direct T-cell function and improve the efficacy of cancer vaccination and immunotherapy.

IL-10 Signaling Elicited by Nivolumab-Induced Activation of the MAP Kinase Pathway Does Not Fully Contribute to Nivolumab-Modulated Heterogeneous T Cell Responses

Immune checkpoint inhibitor (ICI) therapy has revolutionized anti-cancer treatment for many late-stage cancer patients. However, ICI therapy has thus far demonstrated limited efficacy for most patients, and it remains unclear why this is so. Interleukin 10 (IL-10) is a cytokine that has been recognized as a central player in cancer biology with its ability to inhibit anti-tumor T cell responses. Recent studies suggest that IL-10 might also exert some intrinsic anti-tumor T cell responses, and clinical studies using recombinant IL-10 alone or in combination with ICI are underway. This paradoxical effect of IL-10 and its underlying mechanisms impacting ICI-modulated T cell responses remain poorly understood. In this study, using an in vitro mixed lymphocyte reaction assay, we found that treatment with ICIs such as the anti-programmed cell death receptor-1 (PD-1) mAb nivolumab elicits a strong expression of IL-10. While neutralization of IL-10 signaling with an anti-IL-10 specific mAb significantly decreases the production of IFN-γ by T cells in a cohort of donor cells, the opposite effect was observed in other donor cells. Similarly, neutralization of IL-10 signaling significantly decreases the expression of T cell activation markers Ki67 and CD25, as well as the production of Granzyme B in a cohort of donor cells, whereas the opposite effect was observed in others. Furthermore, we found that nivolumab and IL-10 differentially modulate the signal transducer and activator of transcription 3 (STAT3) and AKT serine–threonine kinase pathways. Finally, we found that nivolumab activates the mitogen-activated protein kinase (MAPK) pathway, which in turn is responsible for the observed induction of IL-10 production by nivolumab. These findings provide new insights into the mechanisms underlying anti-PD-1-modulated T cell responses by IL-10, which could lead to the discovery of novel combination treatments that target IL-10 and immune checkpoint molecules.

BRAF inhibitor resistance of melanoma cells triggers increased susceptibility to natural killer cell-mediated lysis

Background

Targeted therapies and immunotherapies are first-line treatments for patients with advanced melanoma. Serine–threonine protein kinase B-RAF (BRAF) and mitogen-activated protein kinase (MEK) inhibition leads to a 70% response rate in patients with advanced melanoma with a BRAF^V600E/K mutation. However, acquired resistance occurs in the majority of patients, leading to relapse. Immunotherapies that activate immune cytotoxic effectors induce long-lasting responses in 30% of patients. In that context, combination of targeted therapies with immunotherapy (IT) is a promising approach. We considered boosting natural killer (NK) cell tumor immunosurveillance, as melanoma cells express stress-induced molecules and activate NK cell lysis.

Methods

Here we have generated vemurafenib (a BRAF inihibitor)-resistant (R) cells from BRAF^V600E SK28 and M14-sensitive (S) melanoma cell lines and investigated how resistance interferes with immunogenicity to NK cells. We determined the levels of several soluble molecules including NK ligands in 61 melanoma patients at baseline and 6 months M post-treatment with targeted therapies or immunotherapies.

Results

Vemurafenib resistance involved activation of p-AKT in SK28R and of p-MEK/p-ERK in M14R cells and was accompanied by modulation of NK ligands. Compared with S cells, SK28R displayed an increased expression of natural killer group 2 D (NKG2D) receptor ligands (major histocompatibility complex class (MHC) I chain-related protein A (MICA) and UL16-binding protein 2 (ULBP2)) whereas M14R exhibited decreased ULBP2. SK28R and M14R cells induced higher NK degranulation and interferon gamma secretion and were more efficiently lysed by donor and patient NK cells. SK28R showed increased tumor necrosis factor-related apoptosis-inducing ligand receptor II (TRAIL-RII) expression and TRAIL-induced apoptosis, and TRAIL-induced apoptosis of M14R was decreased. Combined BRAF/MEK inhibitors abrogated the growth of SK28S, M14S, and M14R cells, while growth of SK28R was maintained. BRAF/MEK inhibition attenuated NK activity but R cell lines activated polyfunctional NK cells and were lysed with high efficiency. We investigated the relationship of soluble NK ligands and response to treatment in a series of melanoma patients. Soluble NKG2D ligands known to regulate the receptor function have been associated to cancer progression. Serum analysis of patients treated with target therapies or IT indicates that soluble forms of NK ligands (MICA, B7H6, programmed cell death ligand 1, and carcinoembryonic antigen cell adhesion molecule 1) may correlate with clinical response.

Conclusion

These results support strategies combining targeted therapies and NK-based immunotherapies.

The emerging role of immune checkpoint inhibitors for the treatment of breast cancer

INTRODUCTION

Breast cancer has traditionally been viewed as immunogenically 'cold,' but two immune checkpoint inhibitors have been approved in combination with chemotherapy for PD-L1 positive advanced triple-negative breast cancer (TNBC), and pembrolizumab was also recently approved for early stage TNBC. As the landscape is rapidly evolving, a comprehensive review of checkpoint inhibitors in breast cancer is needed to aid clinicians in selecting appropriate candidates for therapy, and to highlight ongoing promising studies in this area and topics in need of further investigation.

AREA COVERED

This review summarizes the latest evidence from completed and ongoing trials of immune checkpoint inhibitors. Ongoing studies were identified using a search of ClinicalTrials.gov with the term 'breast cancer' along with specific checkpoint inhibitor agents.

EXPERT OPINION

A number of novel combination strategies are under investigation to enhance response and overcome resistance to immunotherapy, with promising preliminary data from checkpoint inhibitors targeting TIGIT, combinations with small molecule inhibitors such as lenvatinib, and injectable agents directly influencing the immune microenvironment. As immunotherapy enters into the curative setting, biomarkers predictive of immunotherapy benefit are needed, as PD-L1 status has not been a helpful discriminator in completed trials in early-stage breast cancer.

Next-generation immunotherapy for pancreatic ductal adenocarcinoma: navigating pathways of immune resistance

To date, the use of immune checkpoint inhibitors has proven largely ineffective in patients with advanced pancreatic ductal adenocarcinoma. A combination of low tumor antigenicity, deficits in immune activation along with an exclusive and suppressive tumor microenvironment result in resistance to host defensives. However, a deepening understanding of these immune escape and suppressive mechanisms has led to the discovery of novel molecular targets and treatment strategies that may hold the key to a long-awaited therapeutic breakthrough. In this review, we describe the tumor-intrinsic and microenvironmental barriers to modern immunotherapy, examine novel immune-based and targeted modalities, summarize relevant pre-clinical findings and human experience, and, finally, discuss novel synergistic approaches to overcome immune-resistance in pancreatic cancer. Beyond checkpoint inhibition, immune agonists and anti-tumor vaccines represent promising strategies to stimulate host response via activation and expansion of anti-tumor immune effectors. Off-the-shelf natural killer cell therapies may offer an effective method for bypassing downregulated tumor antigen presentation. In parallel with this, sophisticated targeting of crosstalk between tumor and tumor-associated immune cells may lead to enhanced immune infiltration and survival of anti-tumor lymphocytes. A future multimodal treatment strategy involving immune priming/activation, tumor microenvironment reprogramming, and immune checkpoint blockade may help transform pancreatic cancer into an immunogenic tumor.

Context-Dependent Immunomodulatory Effects of MEK Inhibition are Enhanced with T-cell Agonist Therapy

MEK inhibition (MEKi) is proposed to enhance antitumor immunity but has demonstrated mixed results as an immunomodulatory strategy in human clinical trials. MEKi exerts direct immunomodulatory effects on tumor cells and tumor-infiltrating lymphocytes, but these effects have not been independently investigated. Here we modeled tumor-specific MEKi through CRISPR/Cas-mediated genome editing of tumor cells (MEK1 KO) and pharmacologic MEKi with cobimetinib in a RAS-driven model of colorectal cancer. This approach allowed us to distinguish tumor-mediated and tumor-independent mechanisms of MEKi immunomodulation. MEK1 KO tumors demonstrated upregulation of JAK/STAT signaling; enhanced MHCI expression, CD8+ T-cell infiltration and T-cell activation; and impaired tumor growth that is immune-dependent. Pharmacologic MEKi recapitulated tumor-intrinsic effects but simultaneously impaired T-cell activation in the tumor microenvironment. We confirmed a reduction in human peripheral lymphocyte activation from a clinical trial of anti-PD-L1 (atezolizumab) with or without cobimetinib in biliary tract cancers. Impaired activation of tumor-infiltrating lymphocytes treated with pharmacologic MEKi was reversible and was rescued with the addition of a 41BB agonist. Collectively, these data underscore the ability of MEKi to induce context-dependent immunomodulatory effects and suggest that T cell-agonist therapy maximizes the beneficial effects of MEKi on the antitumor immune response.

Inhibition of MEK pathway enhances the antitumor efficacy of chimeric antigen receptor T cells against neuroblastoma

Disialoganglioside (GD2)‐specific chimeric antigen receptor (CAR)‐T cells (GD2‐CAR‐T cells) have been developed and tested in early clinical trials in patients with relapsed/refractory neuroblastoma. However, the effectiveness of immunotherapy using these cells is limited, and requires improvement. Combined therapy with CAR‐T cells and molecular targeted drugs could be a promising strategy to enhance the antitumor efficacy of CAR T cell immunotherapy. Here, we generated GD2‐CAR‐T cells through piggyBac transposon (PB)‐based gene transfer (PB‐GD2‐CAR‐T cells), and analyzed the combined effect of these cells and a MEK inhibitor in vitro and in vivo on neuroblastoma. Trametinib, a MEK inhibitor, ameliorated the killing efficacy of PB‐GD2‐CAR‐T cells in vitro, whereas a combined treatment of the two showed superior antitumor efficacy in a murine xenograft model compared to that of PB‐GD2‐CAR‐T cell monotherapy, regardless of the mutation status of the MAPK pathway in tumor cells. The results presented here provide new insights into the feasibility of combined treatment with CAR‐T cells and MEK inhibitors in patients with neuroblastoma.

p38 MAPK signaling in M1 macrophages results in selective elimination of M2 macrophages by MEK inhibition

M2 macrophages promote tumor progression and therapy resistance, whereas proimmunogenic M1 macrophages can contribute to the efficacy of cytostatic and immunotherapeutic strategies. The abundance of M2 macrophages in the immune infiltrate of many cancer types has prompted the search for strategies to target and eliminate this subset. From our prior experiments in syngeneic mouse tumor models, we learned that pharmacological inhibition of mitogen-activated protein kinase kinase (MEK) did not merely result in tumor cell death, but also in the modulation of the tumor immune infiltrate. This included a prominent decrease in the numbers of macrophages as well as an increase in the M1/M2 macrophage ratio. Investigation of the mechanism underlying this finding in primary murine macrophage cultures revealed that M2 macrophages are significantly more sensitive to MEK inhibition-induced cell death than their M1 counterparts. Further analyses showed that the p38 MAPK pathway, which is activated in M1 macrophages only, renders these cells resistant to death by MEK inhibition. In conclusion, the dependency of M2 macrophages on the MEK/extracellular-signal regulated kinase (ERK) pathway empowers MEK inhibitors to selectively eliminate this subset from the tumor microenvironment.

Integrated transcriptional-phenotypic analysis captures systemic immunomodulation following antiangiogenic therapy in renal cell carcinoma patients

BACKGROUND

The combination of immune checkpoint blockade (ICB) with standard therapies is becoming a common approach for overcoming resistance to cancer immunotherapy in most human malignancies including metastatic renal cell carcinoma (mRCC). In this regard, insights into the immunomodulatory properties of antiangiogenic agents may help designing multidrug schedules based on specific immune synergisms.

METHODS

We used orthogonal transcriptomic and phenotyping platforms combined with functional analytic pipelines to elucidate the immunomodulatory effect of the antiangiogenic agent pazopanib in mRCC patients. Nine patients were studied longitudinally over a period of 6 months. We also analyzed transcriptional data from The Cancer Genome Atlas (TCGA) RCC cohort (N = 571) to assess the prognostic implications of our findings. The effect of pazopanib was assessed in vitro on NK cells and T cells. Additionally, myeloid-derived suppressor (MDSC)-like cells were generated from CD14+ monocytes transfected with mimics of miRNAs associated with MDSC function in the presence or absence of pazopanib.

RESULTS

Pazopanib administration caused a rapid and dramatic reshaping in terms of frequency and transcriptional activity of multiple blood immune cell subsets, with a downsizing of MDSC and regulatory T cells in favor of a strong enhancement in PD-1 expressing cytotoxic T and Natural Killer effectors. These changes were paired with an increase of the expression of transcripts reflecting activation of immune-effector functions. This immunomodulation was marked but transient, peaking at the third month of treatment. Moreover, the intratumoral expression level of a MDSC signature (MDSC INT) was strongly associated with poor prognosis in RCC patients. In vitro experiments indicate that the observed immunomodulation might be due to an inhibitory effect on MDSC-mediated suppression, rather than a direct effect on NK and T cells.

CONCLUSIONS

The marked but transient nature of this immunomodulation, peaking at the third month of treatment, provides the rationale for the use of antiangiogenics as a preconditioning strategy to improve the efficacy of ICB.

Tumor-infiltrating CD8+ T cell antitumor efficacy and exhaustion: molecular insights

Host immunity has an essential role in the clinical management of cancers. Therefore, it is advantageous to choose therapies that can promote tumor cell death and concurrently boost host immunity. The dynamic tumor microenvironment (TME) determines whether an antineoplastic drug will elicit favorable or disparaging immune responses from tumor-infiltrating lymphocytes (TILs). CD8+ T cells are one of the primary tumor-infiltrating immune cells that deliver antitumor responses. Here, we review the influence of various factors in the TME on CD8+ T cell exhaustion and survival, and possible strategies for restoring CD8+ T cell effector function through immunotherapy.

Integrative pharmacological mechanism of vitamin C combined with glycyrrhizic acid against COVID-19: findings of bioinformatics analyses

OBJECTIVE

Coronavirus disease 2019 (COVID-19) is a fatal and fast-spreading viral infection. To date, the number of COVID-19 patients worldwide has crossed over six million with over three hundred and seventy thousand deaths (according to the data from World Health Organization; updated on 2 June 2020). Although COVID-19 can be rapidly diagnosed, efficient clinical treatment of COVID-19 remains unavailable, resulting in high fatality. Some clinical trials have identified vitamin C (VC) as a potent compound pneumonia management. In addition, glycyrrhizic acid (GA) is clinically as an anti-inflammatory medicine against pneumonia-induced inflammatory stress. We hypothesized that the combination of VC and GA is a potential option for treating COVID-19.

METHODS

The aim of this study was to determine pharmacological targets and molecular mechanisms of VC + GA treatment for COVID-19, using bioinformational network pharmacology.

RESULTS

We uncovered optimal targets, biological processes and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways of VC + GA against COVID-19. Our findings suggested that combinatorial VC and GA treatment for COVID-19 was associated with elevation of immunity and suppression of inflammatory stress, including activation of the T cell receptor signaling pathway, regulation of Fc gamma R-mediated phagocytosis, ErbB signaling pathway and vascular endothelial growth factor signaling pathway. We also identified 17 core targets of VC + GA, which suggest as antimicrobial function.

CONCLUSIONS

For the first time, our study uncovered the pharmacological mechanism underlying combined VC and GA treatment for COVID-19. These results should benefit efforts to address the most pressing problem currently facing the world.

Immunomodulation by targeted anticancer agents

At odds with conventional chemotherapeutics, targeted anticancer agents are designed to inhibit precise molecular alterations that support oncogenesis or tumor progression. Despite such an elevated degree of molecular specificity, many clinically employed and experimental targeted anticancer agents also mediate immunostimulatory or immunosuppressive effects that (at least in some settings) influence therapeutic efficacy. Here, we discuss the main immunomodulatory effects of targeted anticancer agents and explore potential avenues to harness them in support of superior clinical efficacy.

Prebiotic-Induced Anti-tumor Immunity Attenuates Tumor Growth

Growing evidence supports the importance of gut microbiota in the control of tumor growth and response to therapy. Here, we select prebiotics that can enrich bacterial taxa that promote anti-tumor immunity. Addition of the prebiotics inulin or mucin to the diet of C57BL/6 mice induces anti-tumor immune responses and inhibition of BRAF mutant melanoma growth in a subcutaneously implanted syngeneic mouse model. Mucin fails to inhibit tumor growth in germ-free mice, indicating that the gut microbiota is required for the activation of the anti-tumor immune response. Inulin and mucin drive distinct changes in the microbiota, as inulin, but not mucin, limits tumor growth in syngeneic mouse models of colon cancer and NRAS mutant melanoma and enhances the efficacy of a MEK inhibitor against melanoma while delaying the emergence of drug resistance. We highlight the importance of gut microbiota in anti-tumor immunity and the potential therapeutic role for prebiotics in this process.

Durable Suppression of Acquired MEK Inhibitor Resistance in Cancer by Sequestering MEK from ERK and Promoting Antitumor T-cell Immunity

MAPK targeting in cancer often fails due to MAPK reactivation. MEK inhibitor (MEKi) monotherapy provides limited clinical benefits but may serve as a foundation for combination therapies. Here, we showed that combining a type II RAF inhibitor (RAFi) with an allosteric MEKi durably prevents and overcomes acquired resistance among cancers with KRAS, NRAS, NF1, BRAF non-V600, and BRAF V600 mutations. Tumor cell-intrinsically, type II RAFi plus MEKi sequester MEK in RAF complexes, reduce MEK/MEK dimerization, and uncouple MEK from ERK in acquired-resistant tumor subpopulations. Immunologically, this combination expands memory and activated/exhausted CD8+ T cells, and durable tumor regression elicited by this combination requires CD8+ T cells, which can be reinvigorated by anti-PD-L1 therapy. Whereas MEKi reduces dominant intratumoral T-cell clones, type II RAFi cotreatment reverses this effect and promotes T-cell clonotypic expansion. These findings rationalize the clinical development of type II RAFi plus MEKi and their further combination with PD-1/L1-targeted therapy. SIGNIFICANCE: Type I RAFi + MEKi are indicated only in certain BRAF V600MUT cancers. In contrast, type II RAFi + MEKi are durably active against acquired MEKi resistance across broad cancer indications, which reveals exquisite MAPK addiction. Allosteric modulation of MAPK protein/protein interactions and temporal preservation of intratumoral CD8+ T cells are mechanisms that may be further exploited.This article is highlighted in the In This Issue feature, p. 521.