Abstract C035: Spatially limited stroma-mediated resistance potentiates targeted therapy resistance through an integration of multiple juxtacrine and paracrine mechanisms

Abstract

Abstract Despite the ability to induce strong clinical responses, therapies that target mutational drivers of oncogenic signaling are not curative in advanced cancers, as a subset of cancer cells is capable of surviving therapy and evolving resistance. While therapy resistance is commonly viewed as a cell-intrinsic phenomenon, multiple factors produced by tumors can also confer strong therapy resistance. In contrast to the detailed elucidation of molecular mediators of cell-intrinsic and stroma-mediated (SM) resistance, the relative importance of cell-intrinsic and SM resistance to in vivo therapeutic responses remains poorly defined. To address this gap of knowledge, we used a well-characterized experimental model of ALK+ lung cancer H3122 cell line that exemplifies a duality observed across common models of targetable cancers. Under standard stroma-free in vitro cultures, H3122 cells can survive under therapeutically relevant concentrations of ALK inhibitors (ALKi), eventually acquiring cell-intrinsic therapy resistance. At the same time, co-culture with stromal fibroblasts drastically reduces the sensitivity of H3122 cells to ALKi, indicating the relevance of SM resistance. To understand the impact of SM resistance on in vivo responses, we sought to identify the mechanism(s) responsible for the therapy-protective effects of stromal fibroblasts, subsequently interrogating the impact of the disruption of this mechanism on in vivo therapeutic responses. Our in vitro studies with a large panel of primary stromal fibroblast isolates identified the HGF-cMET axis as the major mechanism responsible for ALKi desensitization. Surprisingly, xenograft validation studies demonstrated a weak effect of HGF-cMET modulation. Histological analyses of tumor tissues revealed that this relative weakness is attributable to a strong, spatially limited HGF-independent component of SM resistance. Mechanistic follow-up demonstrated that the HGF-independent component of SM resistance integrates the effect of multiple well-known juxtacrine and paracrine-acting mechanisms. Whereas the multifactorial nature of stroma-mediated resistance prevented a clear assessment of its relative contribution to in vivo therapy responses, our spatial analyses indicate that SM resistance dominates the ability of tumors to avoid therapeutic elimination. Surprisingly, we found that SM resistance was also a substantial contributor to tumor relapse, indicating that in vivo therapy resistance can integrate both cell-intrinsic and cell-extrinsic effects. This duality of therapy resistance and the multifactorial underpinning of both cell-intrinsic and stroma-mediated resistance present a challenge to therapeutic strategies focused on identifying and targeting specific resistance mechanisms. Our studies suggest that this limitation can be overcome by shifting the therapeutic focus towards shared orthogonal therapeutic sensitivities of tumor cells within residual disease. Citation Format: Bina Desai, Tatiana Miti, Sandhya Prabhakaran, Daria Miroshnychenko, Menkara Henry, Viktoriya Marusyk, Chandler Gatenbee, Marilyn Bui, Jacob Scott, Philipp M. Altrock, Eric Haura, Alexander R.A. Anderson, David Basanta, Andriy Marusyk. Spatially limited stroma-mediated resistance potentiates targeted therapy resistance through an integration of multiple juxtacrine and paracrine mechanisms [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Tumor-body Interactions: The Roles of Micro- and Macroenvironment in Cancer; 2024 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2024;84(22_Suppl):Abstract nr C035.