Abstract 5117: Combined treatment with the epigenetic drug CM272 and an anti-BCL-XL proapoptotic drug sensitizes solid tumors to immune checkpoint blockade

Epigenetic modulators in combination with proapoptotic drugs have become a standard of treatment for acute myeloid leukemia. However, the clinical efficacy of these combinations in solid tumors has shown to be negligible. Our group has demonstrated that the epigenetic drug CM272, which targets DNMT and G9a, induces synergistic responses in combination with proapoptotic drugs in hematological malignancies (Cancer Discovery 2021). We have also reported that CM272 induces an immunogenic cell death that sensitizes tumor cells to immune checkpoint blockade (ICB) (Nature Medicine 2020). Here, we hypothesized that CM272 in combination with proapoptotic drugs may sensitize tumor cells to ICB, resulting in profound anti-tumor responses. To test this hypothesis, we evaluated in vitro the sensitivity of cancer cells to different combinations of epigenetic and proapoptotic drugs. The most efficient combination was tested in various immunocompetent mouse models, followed by an immunophenotypic characterization of the tumor microenvironment. We found that CM272 in combination with inhibitors of BCL-XL, BCL2 or MCL1, yielded synergistic in vitro responses in a large collection of human and mouse cell lines derived from solid tumors. Mechanistically, the treatments induced the expression of endogenous retroelements/retroviruses, which led to the activation of RIG-1 and MDA5 viral sensors, ATP hydrolysis and tumor cell death. Remarkably, we found that CM272 in combination with BCL-XL inhibition had more potent anti-tumor effects than that found with BCL2 or MCL1 inhibitors. In vivo, the triple combination CM272, A1331852 (BCL-XL inhibitor) and an anti-PD-1 moAb significantly reduced tumor growth and increased overall survival in three subcutaneous lung cancer models (LLC, 393P, Lacun-3) in comparison to double treatments. Moreover, this triple combination also induced significant anti-tumor responses in subcutaneous mouse models of colon cancer (MC38) and melanoma (B16), as well as in orthotopic models of lung cancer (LLC), glioblastoma (CT-2A) and breast cancer (ANV5), leading to prolonged survival and cure in a fraction of animals. The triple therapy was associated with a significant increase in the ratio of CD8 T versus immunosuppressive Treg cells, and M1 versus M2 macrophages. In conclusion, we report a novel regimen combining a dual epigenetic inhibitor, an anti-BCL-XL, and an anti-PD-1 moAb that results in potent responses in multiple pre-clinical models of solid tumors. The mechanisms underneath the antitumor responses include the modulation of the energy metabolism in tumor cells, leading to cell death boosted by an anti-BCL-XL pro-apoptotic drug, along with fostering the immune system to generate an efficient anti-tumor response assisted by ICB. This study reveals the potential of epigenetic therapeutics to treat and cure patients with solid tumors.

Citation Format: Yaiza Senent, Vicente Fresquet, Victoria Jimenez, Karmele Valencia, Ana Remirez, Francisco Exposito, Marisol Gonzalez-Huarriz, Borja Ruiz-Fernandez de Cordoba, Haritz Moreno, Daniel Ajona, Marta M Alonso, Fernando Lecanda, Antonio Pineda-Lucena, Felipe Prosper, Alfonso Calvo, Jose Angel Martinez-Climent, Ruben Pio. Combined treatment with the epigenetic drug CM272 and an anti-BCL-XL proapoptotic drug sensitizes solid tumors to immune checkpoint blockade. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5117.

Tumor ENPP1(CD203a)/Haptoglobin Axis Exploits Myeloid-Derived Suppressor Cells to Promote Post-Radiotherapy Local Recurrence in Breast Cancer

Locoregional failure (LRF) in breast cancer patients post-surgery and post-irradiation (IR) is linked to a dismal prognosis. In a refined new model, we identified Enpp1 (Ectonucleotide pyrophosphatase /phosphodiesterase 1/CD203a) to be closely associated with LRF. Enpp1high circulating tumor cells (CTC) contribute to relapse by a self-seeding mechanism. This process requires the infiltration of PMN-MDSC and neutrophil extracellular traps (NET) formation. Genetic and pharmacological Enpp1 inhibition or NET blockade extend relapse-free survival. Furthermore, in combination with fractionated irradiation (FD), Enpp1 abrogation obliterates LRF. Mechanistically, Enpp1-generated adenosinergic metabolites enhance Haptoglobin (Hp) expression. This inflammatory mediator elicits myeloid invasiveness and promotes NET formation. Accordingly, a significant increase in ENPP1 and NET formation is detected in relapsed human breast cancer tumors. Moreover, high ENPP1 or HP levels are associated with poor prognosis. These findings unveil the ENPP1/HP axis as an unanticipated mechanism exploited by tumor cells linking inflammation to immune remodeling favoring local relapse.

FOSL1 promotes cholangiocarcinoma via transcriptional effectors that could be therapeutically targeted

BACKGROUND & AIMS

Cholangiocarcinoma (CCA) is a neoplasia of the biliary tract driven by genetic, epigenetic and transcriptional mechanisms. Herein, we investigated the role of the transcription factor FOSL1, as well as its downstream transcriptional effectors, in the development and progression of CCA.

METHODS

FOSL1 was investigated in human CCA clinical samples. Genetic inhibition of FOSL1 in human and mouse CCA cell lines was performed in in vitro and in vivo models using constitutive and inducible short-hairpin RNAs. Conditional FOSL1 ablation was done using a genetically engineered mouse (GEM) model of CCA (mutant KRAS and Trp53 knockout). Follow-up RNA and chromatin immunoprecipitation (ChIP) sequencing analyses were carried out and downstream targets were validated using genetic and pharmacological inhibition.

RESULTS

An inter-species analysis of FOSL1 in CCA was conducted. First, FOSL1 was found to be highly upregulated in human and mouse CCA, and associated with poor patient survival. Pharmacological inhibition of different signalling pathways in CCA cells converged on the regulation of FOSL1 expression. Functional experiments showed that FOSL1 is required for cell proliferation and cell cycle progression in vitro, and for tumour growth and tumour maintenance in both orthotopic and subcutaneous xenograft models. Likewise, FOSL1 genetic abrogation in a GEM model of CCA extended mouse survival by decreasing the oncogenic potential of transformed cholangiocytes. RNA and ChIP sequencing studies identified direct and indirect transcriptional effectors such as HMGCS1 and AURKA, whose genetic and pharmacological inhibition phenocopied FOSL1 loss.

CONCLUSIONS

Our data illustrate the functional and clinical relevance of FOSL1 in CCA and unveil potential targets amenable to pharmacological inhibition that could enable the implementation of novel therapeutic strategies.

LAY SUMMARY

Understanding the molecular mechanisms involved in cholangiocarcinoma (bile duct cancer) development and progression stands as a critical step for the development of novel therapies. Through an inter-species approach, this study provides evidence of the clinical and functional role of the transcription factor FOSL1 in cholangiocarcinoma. Moreover, we report that downstream effectors of FOSL1 are susceptible to pharmacological inhibition, thus providing new opportunities for therapeutic intervention.