Immunotherapy in colorectal cancer: What have we learned so far?

Autophagy: Dual roles and perspective for clinical treatment of colorectal cancer

Colorectal cancer (CRC) raises concerns to people because of its high recurrence and metastasis rate, diagnosis challenges, and poor prognosis. Various studies have shown the association of altered autophagy with tumorigenesis, tumor-stroma interactions, and resistance to cancer therapy in CRC. Autophagy is a highly conserved cytosolic catabolic process in eukaryotes that plays distinct roles in CRC occurrence and progression. In early tumorigenesis, autophagy may inhibit tumor growth through diverse mechanisms, whereas it exhibits a tumor promoting function in CRC progression. This different functions of autophagy in CRC occurrence and progression make developing therapies targeting autophagy complicated. In this review, we discuss the classification and process of autophagy as well as its dual roles in CRC, functions in the tumor microenvironment, cross-talk with apoptosis, and potential usefulness as a CRC therapeutic target.

An Overview on Immunogenic Cell Death in Cancer Biology and Therapy

Immunogenic cell death (ICD) is a modality of regulated cell death that is sufficient to promote an adaptive immune response against antigens of the dying cell in an immunocompetent host. An important characteristic of ICD is the release and exposure of damage-associated molecular patterns, which are potent endogenous immune adjuvants. As the induction of ICD can be achieved with conventional cytotoxic agents, it represents a potential approach for the immunotherapy of cancer. Here, different aspects of ICD in cancer biology and treatment are reviewed.

Siglec-7 is a predictive biomarker for the efficacy of cancer vaccination against metastatic colorectal cancer

Cancer immunotherapy, including vaccination, is considered a major scientific and medical breakthrough. However, cancer immunotherapy does not result in durable objective responses against colorectal cancer (CRC). To improve the efficacy of immunotherapy, the present study investigated several biomarkers for selecting patients who were expected to respond well to immunotherapy. Firstly, a comprehensive proteomic analysis was performed using tumor tissue lysates from patients enrolled in a phase II study, in which five human leukocyte antigen (HLA)-A*24:02-restricted peptides were administered. Sialic acid-binding immunoglobulin type lectin (Siglec)-7 was identified as a potential predictive biomarker. Subsequently, this biomarker was validated using western blot analysis, and immunofluorescence using tissue samples from the patients enrolled in the phase II study. The expression levels of Siglec-7 detected by immunofluorescence were quantified and their association with overall survival (OS) in patients treated with the peptide vaccine was examined. Furthermore, considering the important role of tumor-infiltrating lymphocytes (TILs) for CRC prognosis, the densities of CD3⁺, CD4^+, CD8⁺ and forkhead box P3 (FOXP3)⁺ T cells in CRC tissues were examined and compared with Siglec-7 expression. The mean expression levels of Siglec-7 were significantly higher in patients with poor prognosis, with an OS of ≤2 years, as shown in comprehensive proteomic analysis (P=0.016) and western blot analysis (P=0.025). Immunofluorescence analysis demonstrated that Siglec-7 was expressed in intratumoral macrophages. The OS in patients with high Siglec-7 expression was significantly shorter than in that in patients with low Siglec-7 expression (P=0.017) in the HLA-A*24:02-matched patients. However, this difference was not observed in the HLA-unmatched patients. There was no significant difference in OS between patients according to the numbers of TILs, nor significant correlation between TILs and Siglec-7 expression. In conclusion, Siglec-7 expression in macrophages in tumor tissue may be a novel predictive biomarker for the efficacy of immunotherapy against metastatic CRC.

Immunotherapy-based combination strategies for treatment of gastrointestinal cancers: current status and future prospects

Strategies in comprehensive therapy for gastrointestinal (GI) cancer have been optimized in the last decades to improve patients' outcomes. However, treatment options remain limited for late-stage or refractory diseases. The efficacy of immune checkpoint inhibitors (ICIs) for treatment of refractory GI cancer has been confirmed by randomized clinical trials. In 2017, pembrolizumab was approved by the US Food and Drug Administration as the first agent for treatment of metastatic solid tumors with mismatch repair deficiency, especially for colorectal cancer. Given the different mechanisms, oncologists have focused on determining whether ICIs-based combination strategies could achieve higher efficacy than conventional therapy alone in late-stage or even front-line treatment of GI cancer. This review discusses the current status of combining immune checkpoint inhibitors with molecular targeted therapy, chemotherapy, or radiotherapy in GI cancer in terms of mechanisms, safety, and efficacy to provide basis for future research.

Low miR200c expression in tumor budding of invasive front predicts worse survival in patients with localized colon cancer and is related to PD-L1 overexpression

At the histological level, tumor budding in colon cancer is the result of cells undergoing at least partial epithelial-to-mesenchymal transition. The microRNA 200 family is an important epigenetic driver of this process, mainly by downregulating zinc-finger E-box binding homeobox (ZEB) and transforming growth factor beta (TGF-β) expression. We retrospectively explored the expression of the miR200 family, and ZEB1 and ZEB2, and their relationship with immune resistance mediated through PD-L1 overexpression. For this purpose, we analyzed a series of 125 colon cancer cases and took samples from two different tumor sites: the area of tumor budding at the invasive front and from the tumor center. We found significant ZEB overexpression and a reduction in miR200 in budding areas, a profile compatible with epithelial-to-mesenchymal transition. In multivariate analysis of the cases with localized disease, low miR200c expression in budding areas, but not at the tumor center, was an adverse tumor-specific survival factor (hazard ratio: 0.12; 95% confidence interval: 0.03-0.81; p = 0.02) independent of the clinical stage of the disease. PD-L1 was significantly overexpressed in the budding areas and its levels correlated with a mesenchymal transition profile. These results highlight the importance of including budding areas among the samples used for biomarker evaluation and provides relevant data on the influence of mesenchymal transition in the immune resistance mediated by PD-L1 overexpression.

Mucosa-associated invariant T cells infiltrate hepatic metastases in patients with colorectal carcinoma but are rendered dysfunctional within and adjacent to tumor microenvironment

Mucosa-associated invariant T (MAIT) cells are innate-like T lymphocytes that are unusually abundant in the human liver, a common site of colorectal carcinoma (CRC) metastasis. However, whether they contribute to immune surveillance against colorectal liver metastasis (CRLM) is essentially unexplored. In addition, whether MAIT cell functions can be impacted by chemotherapy is unclear. These are important questions given MAIT cells' potent immunomodulatory and inflammatory properties. Herein, we examined the frequencies and functions of peripheral blood, healthy liver tissue, tumor-margin and tumor-infiltrating MAIT cells in 21 CRLM patients who received no chemotherapy, FOLFOX, or a combination of FOLFOX and Avastin before they underwent liver resection. We found that MAIT cells, defined as CD3ε+Vα7.2+CD161++ or CD3ε+MR1 tetramer+ cells, were present within both healthy and tumor-afflicted hepatic tissues. Paired and grouped analyses of samples revealed the physical proximity of MAIT cells to metastatic lesions to drastically influence their functional competence. Accordingly, unlike those residing in the healthy liver compartment, tumor-infiltrating MAIT cells failed to produce IFN-γ in response to a panel of TCR and cytokine receptor ligands, and tumor-margin MAIT cells were only partially active. Furthermore, chemotherapy did not account for intratumoral MAIT cell insufficiencies. Our findings demonstrate for the first time that CRLM-penetrating MAIT cells exhibit wide-ranging functional impairments, which are dictated by their physical location but not by preoperative chemotherapy. Therefore, we propose that MAIT cells may provide an attractive therapeutic target in CRC and that their ligands may be combined with chemotherapeutic agents to treat CRLM.

Molecular Markers for Colorectal Cancer

Colorectal cancers develop through at least 3 major pathways, including chromosomal instability, mismatch repair, and methylator phenotype. These pathways can coexist in a single individual and occur in both sporadic and inherited colorectal cancers. In spite of the unique molecular and genetic signatures of colorectal cancers, nonspecific chemotherapy based on the antineoplastic effects of 5-fluorouracil is the cornerstone of therapy for stage III and some stage II disease. Techniques to recognize colorectal cancer at the molecular level have facilitated development of new signature drugs designed to inhibit the unique pathways of colorectal cancer growth and immunity.

Secretion metabolites of probiotic yeast, Pichia kudriavzevii AS-12, induces apoptosis pathways in human colorectal cancer cell lines

There is a common agreement on the important role of the gastrointestinal microbiota in the etiology of cancer. Benign probiotic yeast strains are able to ameliorate intestinal microbiota and regulate the host metabolism, physiology, and immune system through anti-inflammatory, antiproliferative, and anticancer effects. We hypothesized that Pichia kudriavzevii AS-12 secretion metabolites possess anticancer activity on human colorectal cancer cells (HT-29, Caco-2) via inhibiting growth and inducing apoptosis. This study aimed to assess the anticancer effect of P. kudriavzevii AS-12 secretion metabolites and the underlying mechanisms. The cytotoxicity evaluations were performed via 3-(4,5-dimethylthiazole-2-yl)-2,5-diphenyltetrazolium bromide assay; 4',6-diamidino-2-phenylindole staining; and FACS-flow cytometry tests. Also, the effects of P. kudriavzevii AS-12 secretion metabolites on the expression level of 6 important genes (BAD, Bcl-2, Caspase-3, Caspase-8, Caspase-9 and Fas-R) involved in the extrinsic and intrinsic apoptosis pathways were studied by real-time polymerase chain reaction method. P. kudriavzevii AS-12 secretion metabolites showed significant (P < .0001) cytotoxic effects on HT-29 cells (57.5%) and Caco-2 (32.5%) compared to KDR/293 normal cells (25%). Moreover, the cytotoxic effects of examined yeast supernatant on HT-29 cells were comparable with 5-fluorouracil, as a positive control (57.5% versus 62.2% respectively). Flow cytometric results showed that the induction of apoptosis is the main mechanism of the anticancer effects. Also, according to the reverse transcriptase polymerase chain reaction results, the expression level of proapoptotic genes (BAD, Caspase-3, Caspase-8, Caspase-9, and Fas-R) in treated HT-29 and Caco-2 cells was higher than untreated and normal cells, whereas the antiapoptotic gene (Bcl-2) was downregulated. P. kudriavzevii AS-12 secretion metabolites exert its anticancer effects by inhibiting cell proliferation and inducing intrinsic and extrinsic apoptosis in colon cancer cells.

New frontiers in the treatment of colorectal cancer: Autophagy and the unfolded protein response as promising targets

Colorectal cancer (CRC), despite numerous therapeutic and screening attempts, still remains a major life-threatening malignancy. CRC etiology entails both genetic and environmental factors. Macroautophagy/autophagy and the unfolded protein response (UPR) are fundamental mechanisms involved in the regulation of cellular responses to environmental and genetic stresses. Both pathways are interconnected and regulate cellular responses to apoptotic stimuli. In this review, we address the epidemiology and risk factors of CRC, including genetic mutations leading to the occurrence of the disease. Next, we discuss mutations of genes related to autophagy and the UPR in CRC. Then, we discuss how autophagy and the UPR are involved in the regulation of CRC and how they associate with obesity and inflammatory responses in CRC. Finally, we provide perspectives for the modulation of autophagy and the UPR as new therapeutic options for CRC treatment.

From targeting the tumor to targeting the immune system: Transversal challenges in oncology with the inhibition of the PD-1/PD-L1 axis

After that the era of chemotherapy in the treatment of solid tumors have been overcome by the "translational era", with the innovation introduced by targeted therapies, medical oncology is currently looking at the dawn of a new "immunotherapy era" with the advent of immune checkpoint inhibitors (CKI) antibodies. The onset of PD-1/PD-L1 targeted therapy has demonstrated the importance of this axis in the immune escape across almost all human cancers. The new CKI allowed to significantly prolong survival and to generate durable response, demonstrating remarkable efficacy in a wide range of cancer types. The aim of this article is to review the most up to date literature about the clinical effectiveness of CKI antibodies targeting PD-1/PD-L1 axis for the treatment of advanced solid tumors and to explore transversal challenges in the immune checkpoint blockade.