Cytotoxic chemotherapeutic agents and the EGFR-TKI osimertinib induce calreticulin exposure in non-small cell lung cancer

Clinical application of immunogenic cell death inducers in cancer immunotherapy: turning cold tumors hot

Immunotherapy has emerged as a promising cancer treatment option in recent years. In immune "hot" tumors, characterized by abundant immune cell infiltration, immunotherapy can improve patients' prognosis by activating the function of immune cells. By contrast, immune "cold" tumors are often less sensitive to immunotherapy owing to low immunogenicity of tumor cells, an immune inhibitory tumor microenvironment, and a series of immune-escape mechanisms. Immunogenic cell death (ICD) is a promising cellular process to facilitate the transformation of immune "cold" tumors to immune "hot" tumors by eliciting innate and adaptive immune responses through the release of (or exposure to) damage-related molecular patterns. Accumulating evidence suggests that various traditional therapies can induce ICD, including chemotherapy, targeted therapy, radiotherapy, and photodynamic therapy. In this review, we summarize the biological mechanisms and hallmarks of ICD and introduce some newly discovered and technologically innovative inducers that activate the immune system at the molecular level. Furthermore, we also discuss the clinical applications of combing ICD inducers with cancer immunotherapy. This review will provide valuable insights into the future development of ICD-related combination therapeutics and potential management for "cold" tumors.

Potential of fluoropyrimidine to be an immunologically optimal partner of immune checkpoint inhibitors through inducing immunogenic cell death for thoracic malignancies

BACKGROUND

Immune checkpoint inhibitors (ICIs) are a revolutionary paradigm in the treatment of thoracic malignancies and chemoimmunotherapy is a current standard care in this field. Chemotherapeutic agents are known to induce not only direct cytotoxic effects on tumor cells but also immune modulating effects, such as stimulating immunogenic cell death (ICD). Currently, either pemetrexed (PEM) or taxane plus platinum are combined with ICIs for patients with non-small cell lung cancer (NSCLC); however, it is still unknown whether these agents are immunologically optimal partners for ICIs.

METHODS

To determine the immunologically optimal chemotherapeutic agent, we first evaluated the ability of several chemotherapeutic agents, including platinum, PEM, taxane, and 5-fluorouracil (5-FU) to induce ICD using several thoracic tumor cell lines in vitro. ICD was evaluated by the cell surface expression of calreticulin (CRT) and adenosine-triphosphate (ATP) secretion. We further performed an antitumor vaccination assay in vivo.

RESULTS

5-FU induced cell surface expression of CRT and ATP secretion most efficiently among the several chemotherapeutic agents. This effect was enhanced when it was combined with platinum. In the antitumor vaccination assay in vivo, we found that vaccination with dying-AB1-HA (a murine malignant mesothelioma cell line) cells treated with 5-FU, but neither PEM nor PTX, reduced the tumor growth of living-AB1-HA cells inoculated 1 week after vaccination by recruiting CD3+ CD8+ T cells into the tumor microenvironment.

CONCLUSION

Our findings indicate that fluoropyrimidine can be an immunologically optimal partner of ICIs through the induction of ICD for thoracic malignancies.

Predictive Impact of Diffuse Positivity for TTF-1 Expression in Patients Treated With Platinum-Doublet Chemotherapy Plus Immune Checkpoint Inhibitors for Advanced Nonsquamous NSCLC

Introduction

Pervious studies reported the association of TTF-1 expression with the efficacy of platinum-doublet chemotherapy in combination with immune checkpoint inhibitors in advanced nonsquamous NSCLC. Nevertheless, the predictive value of extent of TTF-1 expression (diffuse or focal TTF-1 positivity) remains unclear.

Methods

The present study retrospectively reviewed 74 patients with TTF-1-positive recurrent or advanced nonsquamous NSCLC receiving first-line chemoimmunotherapy in a single institution in Japan. TTF-1 expression score in pretreatment tumor specimens was evaluated using immunohistochemistry, and the impact of chemoimmunotherapy response was analyzed.

Results

In the total cohort, ≥50% of the tumor cells were TTF-1 positive (i.e., diffusely TTF-1 positive) in specimens of 61 patients (82.4%), whereas 10% to 49% of the tumor cells were TTF-1 positive (i.e., focally TTF-1 positive) in specimens of the remaining 13 patients (17.6%). In multivariate analysis, the median progression-free survival and overall survival (OS) were significantly longer in patients with diffusely TTF-1-positive tumors than in those with focally TTF-1-positive tumors (14.2 versus 9.2 mo, p = 0.01 and 30.2 versus 17.3 mo, p = 0.01, respectively). Moreover, the median OS was significantly longer in patients receiving chemoimmunotherapy including pemetrexed than in those receiving chemoimmunotherapy not including pemetrexed among the patients with diffusely TTF-1-positive tumors (not attained versus 23.2 mo, p < 0.01).

Conclusions

The positive extent of diffuse TTF-1 expression associated with patient outcome was an independent predictive factor for better progression-free survival and OS in patients with advanced nonsquamous NSCLC receiving chemoimmunotherapy.

Calreticulin as a marker and therapeutic target for cancer

Calreticulin (CRT) is a multifunctional protein found within the endoplasmic reticulum (ER). In addition, CRT participates in the formation and development of tumors and promotes the proliferation and migration of tumor cells. When a malignant tumor occurs in the human body, cancer cells that die from immunogenic cell death (ICD) expose CRT on their surface, and CRT that is transferred to the cell surface represents an "eat me" signal, which promotes dendritic cells to phagocytose the tumor cells, thereby increasing the sensitivity of tumors to anticancer immunotherapy. Expression of CRT in tumor tissues is higher than in normal tissues and is associated with disease progression in many malignant tumors. Thus, the dysfunctional production of CRT can promote tumorigenesis because it disturbs not only the balance of healthy cells but also the body's immune surveillance. CRT may be a diagnostic marker and a therapeutic target for cancer, which is discussed extensively in this review.

Impact of increased plasma levels of calreticulin on prognosis of patients with advanced lung cancer undergoing combination treatment of chemotherapy and immune checkpoint inhibitors

BACKGROUND

Damage-associated molecular pattern (DAMP)-related immunogenic cell death triggers secondary adaptive immune responses. The relationship between DAMP levels and prognosis in patients with non-small cell lung cancer (NSCLC) who undergo a combination therapy of immune checkpoint inhibitors (ICI) and chemotherapy remains unclear.

METHODS

Serial plasma samples were prospectively collected from 45 patients treated with ICI combination therapy for advanced NSCLC. Plasma concentrations of high-mobility group box 1 (HMGB1), calreticulin (CRT), annexin A1, and heat shock protein 70 were measured. Associations between increases in plasma DAMP levels and the efficacy of the ICI combination therapy were evaluated.

RESULTS

The maximum fold changes in plasma levels differed across individuals but demonstrated a marked increase, especially for CRT (mean ± SEM, 11.61 ± 46.15). Increased plasma DAMP levels were not clearly associated with clinical responses. There was a significant correlation between the maximum fold change in CRT levels and progression-free survival (PFS; r = 0.49, P < 0.001). Median PFS and overall survival (OS) rates were higher in patients with a ≥ 2-fold increase in plasma CRT levels than in those with a < 2-fold increase (PFS, 14.9 versus 6.0 months, hazard ratio (HR), 0.58; P = 0.17; OS, not reached versus 21.6 months, HR, 0.31, P = 0.02).

CONCLUSIONS

Plasma CRT level monitoring has the potential to predict the efficacy of ICI combination therapy and shed light on the mechanisms underlying DAMP-related immunogenic cell death.

Dynamic polarization of tumor-associated macrophages and their interaction with intratumoral T cells in an inflamed tumor microenvironment: from mechanistic insights to therapeutic opportunities

Immunotherapy has brought a paradigm shift in the treatment of tumors in recent decades. However, a significant proportion of patients remain unresponsive, largely due to the immunosuppressive tumor microenvironment (TME). Tumor-associated macrophages (TAMs) play crucial roles in shaping the TME by exhibiting dual identities as both mediators and responders of inflammation. TAMs closely interact with intratumoral T cells, regulating their infiltration, activation, expansion, effector function, and exhaustion through multiple secretory and surface factors. Nevertheless, the heterogeneous and plastic nature of TAMs renders the targeting of any of these factors alone inadequate and poses significant challenges for mechanistic studies and clinical translation of corresponding therapies. In this review, we present a comprehensive summary of the mechanisms by which TAMs dynamically polarize to influence intratumoral T cells, with a focus on their interaction with other TME cells and metabolic competition. For each mechanism, we also discuss relevant therapeutic opportunities, including non-specific and targeted approaches in combination with checkpoint inhibitors and cellular therapies. Our ultimate goal is to develop macrophage-centered therapies that can fine-tune tumor inflammation and empower immunotherapy.

Immunogenic cell death (ICD)-inducers in non-small-cell lung carcinoma (NSCLC): current knowledge and future perspective

The prevalence of non-small-cell lung cancer (NSCLC) is rising every year all around the world. The interaction between cancer cells and the tumor microenvironment (TME) is a crucial factor in determining the development of human neoplasms. Organellar and cellular stress are induced during immunogenic cell death (ICD), a particularly functional response pattern. ICD is a separate but poorly characterized entity caused by various cancer treatments. The induction of ICD has the potential to change TME and the recruitment of tumor-infiltrating lymphocytes (TILs), and the coupling of ICD-inducers and other therapeutic approaches can have a synergistic role in boosting anticancer impacts. The purpose of this study is to review the studies in the field of NSCLC using ICD-inducers as a treatment strategy or as a combination therapy. This review provide for researches a better view of what has been done so far and the challenges they face in the future.

The application basis of immuno-checkpoint inhibitors combined with chemotherapy in cancer treatment

Immuno-checkpoint inhibitors (ICIs) bring a promising prospect for patients with cancers, which restrains the growth of tumor cells by enhancing anti-tumor activity. Nevertheless, not all patients benefit from the administration of ICIs monotherapy. The partial response or resistance to ICIs is mainly due to the complex and heterogenous tumor microenvironment (TME). The combined therapy is necessary for improving the efficacy of tumor treatment. Chemotherapy is reported not only to kill tumor cells directly, but also to stimulate effective anti-tumor immune responses. Several combined therapies of ICIs and chemotherapeutic agents have been approved for the first-line treatment of cancers, including PD-1/PD-L1 inhibitors. This review summarizes the potential mechanisms of the combined therapy of ICIs and chemotherapeutic agents in inducing immunogenic cell death (ICD) and reprogramming TME, and elucidates the possible anti-tumor effects of combined therapy from the perspective of metabolic reprogramming and microbiome reprogramming.

Impact of Results of TTF-1 Immunostaining on Efficacy of Platinum-Doublet Chemotherapy in Japanese Patients with Nonsquamous Non-Small-Cell Lung Cancer

BACKGROUND

Pemetrexed is a key drug in chemotherapy for nonsquamous non-small-cell lung cancer (nonsq NSCLC). Several studies have reported thyroid transcription factor-1 (TTF-1) as a biomarker of the efficacy in chemotherapy regimens, including pemetrexed in non-Asian people.

OBJECTIVE

We aimed to examine the impact of the results of the TTF-1 immunostaining of tumor cells on the therapeutic effect of chemotherapy in Japanese patients with nonsq NSCLC.

METHODS

We examined the results of TTF-1 immunostaining and the clinical background of Japanese patients with nonsq NSCLC who received platinum-doublet chemotherapy at our hospital, from April 2009 to April 2021, and the correlation between regimens with or without pemetrexed in progression-free survival (PFS) and overall survival (OS). The efficacy of each regimen was then compared between TTF-1-positive and TTF-1-negative tumors.

RESULTS

TTF-1 immunostaining was performed in 145 patients during the study period: 92 were positive, and 53 were negative. A total of 24 patients presented with EGFR/ALK gene abnormality (16.6%). The PFS and OS of patients who were TTF-1-positive tended to be longer than those of the patients who were TTF-1-negative under either regimen. In other words, patients who were TTF-1-negative were frequently resistant to numerous chemotherapy drugs and experienced a poor prognosis under both regimens. The OS of patients who were TTF-1-positive and treated with the pemetrexed regimen was significantly longer than those on regimens without pemetrexed (963 vs. 412 days, HR = 0.73; 95% CI 0.55-0.96, p = 0.022), whereas there was no difference in PFS.

CONCLUSIONS

The positivity of TTF-1 immunostaining in tumors could be a predominant prognostic marker for patients who have advanced nonsq NSCLC. Our analysis examined the possibility of a pemetrexed regimen leading to a longer prognosis in Asian patients who were TTF-1-positive for nonsq NSCLC, as shown in previous studies.

From targeted therapy to a novel way: Immunogenic cell death in lung cancer

Lung cancer (LC) is one of the most incident malignancies and a leading cause of cancer mortality worldwide. Common tumorigenic drivers of LC mainly include genetic alterations of EGFR, ALK, KRAS, BRAF, ROS1, and MET. Small inhibitory molecules and antibodies selectively targeting these alterations or/and their downstream signaling pathways have been approved for treatment of LC. Unfortunately, following initial positive responses to these targeted therapies, a large number of patients show dismal prognosis due to the occurrence of resistance mechanisms, such as novel mutations of these genes and activation of alternative signaling pathways. Over the past decade, it has become clear that there is no possible cure for LC unless potent antitumor immune responses are induced by therapeutic intervention. Immunogenic cell death (ICD) is a newly emerged concept, a form of regulated cell death that is sufficient to activate adaptive immune responses against tumor cells. It transforms dying cancer cells into a therapeutic vaccine and stimulates long-lasting protective antitumor immunity. In this review, we discuss the key targetable genetic aberrations and the underlying mechanism of ICD in LC. Various agents inducing ICD are summarized and the possibility of harnessing ICD in LC immunotherapy is further explored.