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859 Regression of an immunologically ‘cold’ oral cancer model induced by modulation of the tumor microenvironment with DOXIL, anti-CTLA-4, and radiation
  1. Fabio Henrique Brasil Da Costa1,
  2. Rohan Bhavane2,
  3. Ratna Veeramachaneni1,
  4. Sofia Cortes1,
  5. Sarah L Latka1,
  6. Andrew Badachhape2,
  7. Renuka TR Menon2,
  8. Prajwal Bhandari2,
  9. Ketankumar B Ghaghada2,
  10. Simon Young3,
  11. Ananth V Annapragada2 and
  12. Andrew Sikora1
  1. 1The University of Texas MD Anderson Cancer Center, Houston, TX, USA
  2. 2Baylor College of Medicine and Texas Children’s Hospital, Houston, TX, USA
  3. 3The University of Texas Health Science Center at Houston, Houston, TX, USA
  • Journal for ImmunoTherapy of Cancer (JITC) preprint. The copyright holder for this preprint are the authors/funders, who have granted JITC permission to display the preprint. All rights reserved. No reuse allowed without permission.


Background The immune-suppressive tumor microenvironment (TME) of oral cancer often hinders the effectiveness of standard treatments, including surgery, chemoradiotherapy, and immunotherapy. This is true for the highly aggressive MOC2 syngeneic oral cancer cell line, which promotes a ’cold’ immunological landscape that limits the efficacy of checkpoint inhibition and other immunotherapies. In addition to its direct cytotoxic activity, liposomal doxorubicin (DOXIL) has immune modulatory properties, including modulation of tumor-infiltrating myeloid cell accumulation and polarization. We hypothesized that DOXIL-induced remodeling of the myeloid microenvironment, in combination with radiotherapy, could reverse MOC2 resistance to anti-CTLA-4 and anti-PD-1 checkpoint inhibition.

Methods We utilized the well-described MOC2 syngeneic murine model of oral cancer to grow flank tumors. Mice (n=/>20 for each condition, divided over 2–3 experiments) were randomized to each of the following treatments: DOXIL (I.V.), anti-PD-1 (I.P.), anti-CTLA-4 (I.P.), radiation therapy (3 x 8 Gy), and combinations thereof. Treatments began two weeks after MOC2 inoculation. Tumor growth was monitored twice a week and changes in the TME post-treatment were assessed via flow cytometry. We further investigated DOXIL’s influence on myeloid differentiation and macrophage polarization by culturing murine bone marrow cells with MOC2-conditioned medium in the presence and absence of DOXIL.

Results DOXIL monotherapy potently inhibited tumor growth, but growth resumed shortly after treatment was completed. The combination of DOXIL and anti-CTLA-4, with or without radiation, induced significant anti-tumor activity including complete regressions in most mice. In contrast, anti-CTLA-4 alone or anti-PD-1 and/or radiation (alone or combined with DOXIL) had little effect on tumor growth. Notably, flow cytometry analysis revealed that animals treated with DOXIL displayed nearly a three-fold depletion of MHCII+ macrophages (~23% vs 8% of CD45+ cells. Supporting these observations, in our ex vivo bone marrow cultures, DOXIL also induced a 3–5-fold reduction of the same MHCII+ macrophages, as well a significant decrease in M2 macrophages.

Conclusions Our study indicates that in an aggressive, immunologically cold oral cancer model, a combined approach using DOXIL, anti-CTLA-4, and radiation can instigate robust tumor regression. Potential induction of immunogenic cell death and selective macrophage depletion by DOXIL could contribute to the reshaping of the TME, which, in concert with CTLA-4 blockade and radiation, leading to effective anti-tumor responses. This underlines the significance of combination therapies to overcome resistance to immunotherapy in hard to treat cancer models. Ongoing studies are further defining the specific mechanisms by which DOXIL modulates the TME.

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