Biology subjects

Anastasiou, P.

Publications and source records attributed to Anastasiou, P..

6 recordsLinked to original sources

bioRxiv2025

Leveraging death of drug-sensitive cancer cells to promote immune-mediated bystander killing of subclones of drug-resistant tumor cells

The response of lung cancer patients to drugs targeting the G12C mutant form of KRAS is limited by the development of resistance through multiple mechanisms. In order to achieve lasting benefit with these therapies, effective strategies for tackling the evolution of drug resistance are required. We have developed a preclinical model system to mimic the development of resistance to KRAS G12Ci inhibitors (G12Ci) such as adagrasib and RMC-4998. Treatment of tumours containing a minor subpopulation of resistant cancer cells with G12Ci leads to their rapid outgrowth to replace the drug-sensitive cells within a few weeks. However, when combined with therapies that, at least in part, target the immune response, such as SHP2 inhibitors or PD-1 blockade, drug-resistant cells can be eliminated, even by drug combinations that do not impact their growth in the absence of drug-sensitive cells. This bystander killing of drug-resistant cells when drug-sensitive cells are targeted is dependent on an intact adaptive immune system. Mechanistically, these combination therapies lead to profound remodelling of the tumour immune microenvironment, with influx of T cells recognising a tumour associated antigen shared between drug-resistant and drug-sensitive cancer cells. Promotion of immune-mediated bystander killing of drug-resistant cells may provide a paradigm for tackling the problem of drug resistance in cancer more broadly.

cancer biology↗

bioRxiv2024

Spatial proteomic analysis of a lung cancer model reveals regulatory T cells attenuate KRAS-G12C inhibitor-induced immune responses

We recently showed that lung tumor specific KRAS-G12C inhibition causes remodelling of the tumor immune microenvironment from cold to hot. As a result, KRAS-G12C inhibition is able to synergise with anti-PD-1 treatment, but only in tumor models that were already moderately responsive to immune checkpoint blockade at baseline. To investigate mechanisms that restrain immunotherapy sensitivity in non-responsive tumors, we used multiplex imaging mass cytometry to explore spatial patterns in the tumor microenvironment of the highly immune evasive KRAS mutant murine Lewis Lung Cancer model. Clustering of close neighbour information per cell allowed characterisation of spatial patterns or communities in the tissue. We identified a community harbouring features of localised T-cell activation, where CD4+ and CD8+ T cells and dendritic cells were gathered together. KRAS-G12C inhibition led to increased expression of PD-1 on T cells, CXCL9 expression by dendritic cells, together with increased proliferation and potential cytotoxicity of CD8+ T cells, indicating an effector response. However, we also observed a high incidence of regulatory T cells (Tregs) within this community, which had frequent contact with effector T cells, suggesting that Tregs may be able to dampen anti-tumoral immune responses following KRAS-G12C inhibition. Similar communities were detected in human lung adenocarcinoma clinical samples. Depleting Tregs in vivo with anti-CTLA-4 antibody rescued the anti-tumor immune response and led to enhanced tumor control in combination with anti-PD-1 and KRAS-G12C inhibitor. We therefore propose use of KRAS-G12C inhibitor in combination with Treg depletion as a therapeutic opportunity that increases anti-tumoral immune responses and initiates tumor regression. One sentence summarySpatial analysis identified regulatory T cells as potential source of local T cell repression, mediating resistance to KRAS-G12Ci and anti-PD1 therapy.

cancer biology↗

bioRxiv2024

Combining RASG12C(ON) inhibitor with SHP2 inhibition sensitises immune excluded lung tumours to immune checkpoint blockade: a strategy for turning cold tumours hot

Mutant selective drugs targeting the inactive, GDP-bound form of KRASG12C have been approved for use in lung cancer, but responses are short-lived due to rapid development of resistance. In this study we use a novel covalent tri-complex inhibitor, RMC-4998, that targets RASG12C in its active, GTP-bound form to investigate treatment of KRAS mutant lung cancer in various immune competent mouse models. While this RASG12C(ON) inhibitor was more potent than the KRASG12C(OFF) inhibitor adagrasib, rapid pathway reactivation was still observed. This could be delayed using combined treatment with a SHP2 inhibitor, RMC-4550, which not only impacted RAS pathway signalling within the tumour cells but also remodelled the tumour microenvironment (TME) to be less immunosuppressive and promoted interferon responses. In an inflamed, "hot", mouse model of lung cancer, RASG12C(ON) and SHP2 inhibitors in combination drive durable responses by suppressing tumour relapse and inducing development of immune memory, which can also be induced by combination of RASG12C(ON) and PD-1 inhibitors. In contrast, in an immune excluded, "cold", mouse model of lung cancer, combined RASG12C(ON) and SHP2 inhibition does not cause durable responses, but does sensitise tumours to immune checkpoint blockade, enabling efficient tumour rejection, accompanied by significant TME reorganization, including depletion of immunosuppressive innate immune cells and recruitment and activation of T and NK cells. These preclinical results demonstrate the potential of the combination of RASG12C(ON) inhibitors with SHP2 inhibitors to sensitize anti-PD-1 refractory tumours to immune checkpoint blockade by stimulating anti-tumour immunity as well as by targeting KRAS-driven proliferation in tumour cells.

cancer biology↗

bioRxiv2023

In vivo CRISPR screen identifies KRAS-induced COX-2 as a driver of immune evasion and immunotherapy resistance in lung cancer

Oncogenic KRAS impairs anti-tumour immune responses, but effective strategies to combine KRAS inhibitors and immunotherapies have so far proven elusive. In vivo CRISPR-Cas9 screening in an immunogenic murine lung cancer model identifies mechanisms by which oncogenic KRAS promotes immune evasion, most notably expression of immunosuppressive cyclooxygenase-2 (COX-2) in cancer cells. Oncogenic KRAS was a potent inducer of COX-2 in both mouse and human lung cancer which was suppressed using KRAS inhibitors. COX-2 acting via prostaglandin E2 (PGE2) promotes resistance to immune checkpoint blockade (ICB) in both mouse and human lung adenocarcinoma. Targeting COX-2/PGE2 remodelled the tumour microenvironment by inducing pro-inflammatory polarisation of myeloid cells and influx of activated cytotoxic CD8+ T cells, which increased the efficacy of ICB. Restoration of COX-2 expression contributed to tumour relapse after prolonged KRAS inhibition. We propose testing COX-2/PGE2 pathway inhibitors in combination with KRAS G12C inhibition or ICB in patients with KRAS-mutant lung cancer.

cancer biology↗

bioRxiv2021

Therapeutic KRASG12C inhibition drives effective interferon-mediated anti-tumour immunity in immunogenic lung cancers

Recently developed KRASG12C inhibitory drugs are beneficial to lung cancer patients harbouring KRASG12C mutations, but drug resistance frequently develops. Due to the immunosuppressive nature of the signaling network controlled by oncogenic KRAS, these drugs can indirectly affect anti-tumour immunity, providing a rationale for their combination with immune checkpoint blockade. In this study, we have characterised how KRASG12C inhibition reverses immune suppression driven by oncogenic KRAS in a number of pre-clinical lung cancer models with varying levels of immunogenicity. Mechanistically, KRASG12C inhibition upregulates interferon signaling via Myc inhibition, leading to reduced tumour infiltration by immunosuppressive cells, enhanced infiltration and activation of cytotoxic T cells, and increased antigen presentation. However, the combination of KRASG12C inhibitors with immune checkpoint blockade only provides synergistic benefit in the most immunogenic tumour model. KRASG12C inhibition fails to sensitize cold tumours to immunotherapy, with implications for the design of clinical trials combining KRASG12C inhibitors with anti-PD1 drugs. One sentence summaryKRAS inhibition mobilizes anti-tumour immunity in immunogenic lung cancer models through derepressing interferon signaling via repression of Myc.

cancer biology↗

bioRxiv2020

Preventing cancer by long-term partial Myc suppression

Myc+/- haploinsufficient mice and mice with deleted Myc enhancers express reduced levels of the pleiotropic transcription factor Myc. Such mice are viable, with relatively mild pathologies, but show delay in onset of certain cancers. However, many phenotypes arising from germline gene perturbation are indirect consequences of adaptive developmental compensation and so do not translate to equivalent phenotypes when applied to adults. To ascertain whether systemic Myc hypomorphism also conferred cancer protection when acutely imposed in adults, and what the side-effects of this might be, we constructed a genetically engineered mouse model in which Myc expression may be systemically and reversibly hypomorphed at will. Acute imposition of Myc hypomorphism in adult mice conferred potent protection against both KRasG12D-driven lung and pancreatic cancers yet elicited only mild haematopoietic side effects. These side effects were completely suppressed by imposing Myc hypomorphism metronomically - a regimen that nonetheless retained potent cancer prophylaxis. Our data identify a key bottleneck at the transition from pre-malignant hyperplasia to overt tumour that is peculiarly reliant on levels of Myc that are higher than those required for most adult physiology, offering a possible window of opportunity for Myc inhibition in cancer prophylaxis.

cancer biology↗