Cancer resistance to therapy by tissue-level homeostatic feedback
Cancer displays remarkable robustness, exemplified by its ability to develop resistance to virtually every therapy. Resistance has traditionally been explained by clonal selection of pre-existing mutations, but there is now abundant evidence for resistance by non-genetic pathways including signals from normal stromal and immune cells. It is largely unclear why normal cells help cancer cells overcome treatment. We propose that physiological circuits responsible for tissue homeostasis can explain why cells cooperate to produce pathological resistance to therapy. To show this, we construct mathematical models of physiological dynamics. We then simulate cancer treatments within the context of a functioning tissue. We find that classic examples of resistance to therapy can be explained by homeostatic feedback regulation - including BRAF inhibitors in melanoma and anti-angiogenic therapy. The homeostatic theory of resistance (HTOR) reframes resistance as a byproduct of tissue robustness, rather than solely tumor-specific adaptation. Finally, we analyze two large-scale single-cell RNAseq databases of normal and cancer samples: the Tabula Sapiens1 and the Curated Cancer Atlas2. We show that in multiple cancers (breast, colon, kidney, liver, lung, ovary, prostate, and skin), malignant cells preserve their tissue-specific homeostatic cell-signaling. We thus expect the robust feedback loops from healthy tissues to play a role in cancer.