Impact of RAS mutations on the immune infiltrate of colorectal liver metastases: A preliminary study

Differential landscape of immune evasion in oncogenic RAS-driven primary and metastatic colorectal cancers

Oncogenic drivers such as KRAS extensively modulate the tumor inflammatory microenvironment (TIME) of colorectal cancer (CRC). The influence of KRAS on modulating immune cell composition remains unclear. The objective of this study was to identify signatures of infiltrative immune cells and distinctive patterns that differ between RAS wild-type (WT) and oncogenic mutant (MT) CRC that explain immune evasion in MT tumors. A total of 7,801 CRC specimens were analyzed using next-generation DNA sequencing, whole-exome sequencing, and/or whole transcriptome sequencing. Deficiency of mismatch repair (dMMR)/microsatellite instability (MSI) and tumor mutation burden (TMB) were also assessed. KRAS mutations were present in 48% of CRC, similarly distributed in patients younger than vs. 50 years and older. In microsatellite stable (MSS) KRAS MT tumors, composition of the TIME included higher neutrophil infiltration and lower infiltration of B cells. MSI-H/dMMR was significantly more prevalent in RAS WT (9.1%) than in KRAS MT (2.9%) CRC. In MSS CRC, TMB-high cases were significantly higher in RAS MT (3.1%) than in RAS WT (2.1%) tumors. KRAS and NRAS mutations are associated with increased neutrophil infiltration, with codon-specific differences. These results demonstrate significant differences in the TIME of RAS mutant CRC that match previous reports of immunoevasive characteristics of such tumors.

Unveiling the role of KRAS in tumor immune microenvironment

Kirsten rats sarcoma viral oncogene (KRAS), the first discovered human oncogene, has long been recognized as "undruggable". KRAS mutations frequently occur in multiple human cancers including non-small cell lung cancer(NSCLC), colorectal cancer(CRC) and pancreatic ductal adenocarcinoma(PDAC), functioning as a "molecule switch" determining the activation of various oncogenic signaling pathways. Except for its intrinsic pro-tumorigenic role, KRAS alteration also exhibits an unique immune signature characterized by elevated PD-L1 level and high tumor mutational burden(TMB). KRAS mutation shape an immune suppressive microenvironment by impeding effective T cells infiltration and recruiting suppressive immune cells including myeloid-derived suppressor cells(MDSCs), regulatory T cells(Tregs), cancer associated fibroblasts(CAFs). In immune checkpoint inhibitor(ICI) era, NSCLC patients with mutated KRAS tend to be more responsive to ICI than patients with intact KRAS. The hallmark for KRAS mutation is the existence of multiple kinds of co-mutations. Different types of co-alterations have distinct tumor microenvironment(TME) signatures and responses to ICI. TP53 co-mutation possess a "hot" TME and achieve higher response to immunotherapy while other loss of function mutation correlated with a "colder" TME and a poor outcome to ICI-based therapy. The groundbreaking discovery of KRAS G12C inhibitors significantly improved outcomes for this KRAS subtype even though efficacy was limited to NSCLC patients. KRAS G12C inhibitors also restore the suppressive TME, creating an opportunity for combinations with ICI. However, an inevitable challenge to KRAS inhibitors is drug resistance. Promising combination strategies such as combination with SHP2 is an approach deserve further exploration because of their immune modulatory effect.

Genetic alterations shape innate immune cells to foster immunosuppression and cancer immunotherapy resistance

Cancer immunotherapy, particularly immune checkpoint inhibitors, has opened a new avenue for cancer treatment following the durable clinical benefits. Despite the clinical successes across several cancer types, primary or acquired resistance might eventually lead to cancer progression in patients with clinical responses. Hence, to broaden the clinical applicability of these treatments, a detailed understanding of the mechanisms limiting the efficacy of cancer immunotherapy is needed. Evidence provided thus far has implicated immunosuppressive innate immune cells infiltrating the tumor microenvironment as key players in immunotherapy resistance. According to the available data, genetic alterations can shape the innate immune response to promote immunotherapy resistance and tumor progression. Herein, this review has discussed the current understanding of the underlying mechanisms where genetic alterations modulate the innate immune milieu to drive immunosuppression and immunotherapy resistance.

Resistin-like beta reduction is associated to low survival rate and is downregulated by adjuvant therapy in colorectal cancer patients

Colorectal Cancer (CRC) is one of the most common cancers accounting for 1.8 million new cases worldwide every year. Therefore, the identification of new potential therapeutic targets represents a continuous challenge to improve survival and quality of CRC patient's life. We performed a microarray analysis dataset consisting of colon biopsies of healthy subjects (HS) and CRC patients. These results were further confirmed in a clinical setting evaluating a series of CRC patients to assess the expression of Resistin-Like Beta (RETNLB) and to correlate it with their clinical data. Our results showed a significant reduction of RETNLB expression in CRC biopsies compared to the HS mucosa. Furthermore, such reduction was significantly associated with the TNM grade and patients' age. Furthermore, a significantly positive correlation was found within mutated subjects for KRAS, TP53, and BRAF. In particular, patients with poor prognosis at 5 years exhibited RETNLB lower levels. In-silico analysis data were confirmed by histochemical analysis in a series of CRC patients recruited by our group. The results obtained provided that RETNLB low levels are associated with an unfavorable prognosis in CRC patients and its expression is also dependent on adjuvant therapy. Further studies are warranted in order to evaluate the molecular mechanisms underlying the role of RETNLB in CRC progression.

Neutrophils and polymorphonuclear myeloid-derived suppressor cells: an emerging battleground in cancer therapy

Neutrophils are central mediators of innate and adaptive immunity and first responders to tissue damage. Although vital to our health, their activation, function, and resolution are critical to preventing chronic inflammation that may contribute to carcinogenesis. Cancers are associated with the expansion of the neutrophil compartment with an escalation in the number of polymorphonuclear myeloid-derived suppressor cells (PMN-MDSC) in the peripheral circulation and tumor microenvironment. Although phenotypically similar to classically activated neutrophils, PMN-MDSC is pathologically activated and immunosuppressive in nature. They dynamically interact with other cell populations and tissue components and convey resistance to anticancer therapies while accelerating disease progression and metastatic spread. Cancer-associated neutrophilia and tumor infiltration of neutrophils are significant markers of poor outcomes in many cancers. Recently, there has been significant progress in the identification of molecular markers of PMN-MDSC providing insights into the central role of PMN-MDSC in the local tumor microenvironment as well as the systemic immune response in cancer. Further advances in sequencing and proteomics techniques will improve our understanding of their diverse functionalities and the complex molecular mechanisms at play. Targeting PMN-MDSC is currently one of the major focus areas in cancer research and several signaling pathways representing possible treatment targets have been identified. Positive results from preclinical studies clearly justify the current investigation in drug development and thus novel therapeutic strategies are being evaluated in clinical trials. In this review, we discuss the involvement of PMN-MDSC in cancer initiation and progression and their potential as therapeutic targets and clinical biomarkers in different cancers.

Chemokines as Regulators of Neutrophils: Focus on Tumors, Therapeutic Targeting, and Immunotherapy

Simple Summary

Neutrophils are the main leukocyte subset present in human blood and play a fundamental role in the defense against infections. Neutrophils are also an important component of the tumor stroma because they are recruited by selected chemokines produced by both cancer cells and other cells of the stroma. Even if their presence has been mostly associated with a bad prognosis, tumor-associated neutrophils are present in different maturation and activation states and can exert both protumor and antitumor activities. In addition, it is now emerging that chemokines not only induce neutrophil directional migration but also have an important role in their activation and maturation. For these reasons, chemokines and chemokine receptors are now considered targets to improve the antitumoral function of neutrophils in cancer immunotherapy.

Abstract

Neutrophils are an important component of the tumor microenvironment, and their infiltration has been associated with a poor prognosis for most human tumors. However, neutrophils have been shown to be endowed with both protumor and antitumor activities, reflecting their heterogeneity and plasticity in cancer. A growing body of studies has demonstrated that chemokines and chemokine receptors, which are fundamental regulators of neutrophils trafficking, can affect neutrophil maturation and effector functions. Here, we review human and mouse data suggesting that targeting chemokines or chemokine receptors can modulate neutrophil activity and improve their antitumor properties and the efficiency of immunotherapy.

KRAS as a Modulator of the Inflammatory Tumor Microenvironment: Therapeutic Implications

KRAS mutations are one of the most frequent oncogenic mutations of all human cancers, being more prevalent in pancreatic, colorectal, and lung cancers. Intensive efforts have been encouraged in order to understand the effect of KRAS mutations, not only on tumor cells but also on the dynamic network composed by the tumor microenvironment (TME). The relevance of the TME in cancer biology has been increasing due to its impact on the modulation of cancer cell activities, which can dictate the success of tumor progression. Here, we aimed to clarify the pro- and anti-inflammatory role of KRAS mutations over the TME, detailing the context and the signaling pathways involved. In this review, we expect to open new avenues for investigating the potential of KRAS mutations on inflammatory TME modulation, opening a different vision of therapeutic combined approaches to overcome KRAS-associated therapy inefficacy and resistance in cancer.

Prophylactic vaccines against cancers of non-infectious origin: a dream or a real possibility?

The dramatic progress in tumour biology and immunology in the past several years has opened new avenues for the treatment and prevention of cancer. One of the great contributions of the immunotherapeutic approaches is an increasing understanding of the immunology of cancer, which is, gradually creating conditions for the development of prophylactic anti-cancer vaccines. Efficient vaccines have been developed and employed for the prophylaxis of two frequent cancers of viral origin, namely cervical cancer and liver cancer. The new knowledge on the interactions between the immune system and the malignant tumors seems to provide means for the development of prophylactic vaccines against cancers developing due to the mutations in the proto-oncogenes converting their products into oncoproteins. According to the present estimates, these cancers form a great majority of human malignancies. Recent evidence has indicated that the immune system recognizes such mutated proteins, and that the development of cancer is due to the failure of the immune system to eliminate neoplastic cells. Followingly, it can be expected that inducing immunity against the mutated epitopes will increase the capacity of the body to deal with the initiated precancerous cells. In the present paper this hypothesis is primarily discussed in the relationship with colorectal cancer (CRC), which seems to be a well-fitting candidate for prophylactic vaccination. CRC is the third most frequent malignancy and the fourth most common cause of cancer mortality. Mutations of two proto-oncogenes, namely RAS and RAF, are involved in the majority of CRC cases and, in addition, they are shared with other human malignancies. Therefore, the strategy to be used for prophylaxis of CRC is discussed together with several other frequent human cancers, namely lung cancer, pancreatic duct cancer and melanoma. The prophylactic vaccines proposed are aimed at the reduction of the incidence of these and, to a lesser extent, some other cancers.

Impact of cancer cell-intrinsic features on neutrophil behavior

Neutrophils are multifaceted innate immune cells that play a significant role in the progression of cancer by exerting both pro- and anti-tumorigenic functions. The crosstalk between cancer cells and neutrophils is complex and emerging evidence is pointing at cancer cell-intrinsic programs regulating neutrophil abundance, phenotype and function. Cancer cell-derived soluble mediators are key players in modulating the interaction with neutrophils. Here, we review how intrinsic features of cancer cells, including cancer cell genetics, epigenetics, signaling, and metabolism, manipulate neutrophil behavior and how to target these processes to impact cancer progression. A molecular understanding of cancer cell-intrinsic properties that shape the crosstalk with neutrophils will provide novel therapeutic strategies for personalized immunomodulation in cancer patients.

The current understanding on the impact of KRAS on colorectal cancer

KRAS (kirsten rat sarcoma viral oncogene) is a member of the RAS family. KRAS mutations are one of most dominant mutations in colorectal cancer (CRC). The impact of KRAS mutations on the prognosis and survival of CRC patients drives many research studies to explore potential therapeutics or target therapy for the KRAS mutant CRC. This review summarizes the current understanding of the pathological consequences of the KRAS mutations in the development of CRC; and the impact of the mutations on the response and the sensitivity to the current front-line chemotherapy. The current therapeutic strategies for treating KRAS mutant CRC, the difficulties and challenges will also be discussed.

Neutrophil diversity and plasticity in tumour progression and therapy

Neutrophils play a key role in defence against infection and in the activation and regulation of innate and adaptive immunity. In cancer, tumour-associated neutrophils (TANs) have emerged as an important component of the tumour microenvironment. Here, they can exert dual functions. TANs can be part of tumour-promoting inflammation by driving angiogenesis, extracellular matrix remodelling, metastasis and immunosuppression. Conversely, neutrophils can also mediate antitumour responses by direct killing of tumour cells and by participating in cellular networks that mediate antitumour resistance. Neutrophil diversity and plasticity underlie the dual potential of TANs in the tumour microenvironment. Myeloid checkpoints as well as the tumour and tissue contexture shape neutrophil function in response to conventional therapies and immunotherapy. We surmise that neutrophils can provide tools to tailor current immunotherapy strategies and pave the way to myeloid cell-centred therapeutic strategies, which would be complementary to current approaches.