Cancer's Backup Pathway Defeats Targeted Therapy

A second survival route inside tumors lets some cancers shrug off tyrosine kinase inhibitors.

MIT researchers have pinpointed why targeted therapies—tyrosine kinase inhibitors—don’t work for all patients who should respond. The drugs typically help only about 40 to 80 percent of patients, and the study shows tumors often flip on a backup survival pathway when the primary pathway is knocked out. “This seems to be hardwired into the cells and seems to be providing activation of a critical survival pathway in cancer cells,” says Forest White, the Ned C. and Janet C. Rice Professor of Biological Engineering. The finding explains a long-standing puzzle: even when a drug shuts down a key signaling route, many tumors keep growing.

The backup pathway is described as a robust failsafe that sustains tumor growth despite inhibition of the intended target. In practical terms, cancer cells aren’t simply downregulated by a single drug; they rewire signaling to keep proliferating and evading therapy. The MIT team, led by White, showed that this alternative route can drive resistance to a broad class of treatments, including chemotherapy. In response, they demonstrated that a combination approach—pairing a tyrosine kinase inhibitor with a drug that targets the backup pathway—can kill those resistant cancer cells.

Clinical translation is already in motion. Clinical trials are underway to test one such combination in lung cancer patients, signaling a potential shift from monotherapy to complementary targeting in a subset of tumors. Cameron Flower PhD ’24, the paper’s lead author and now a postdoc at Dana-Farber Cancer Institute and Boston Children’s Hospital, helped anchor the translational push from cell biology to human trials. The work appears in the Proceedings of the National Academy of Sciences.

From a practical standpoint, the study reframes how clinicians think about response rates to targeted therapies. The 40–80 percent figure isn’t a fixed ceiling; it reflects a population with intrinsic differences in tumor signaling that can undermine a drug’s effect. The discovery of a hardwired backup pathway means that a sizable share of nonresponders may be circumvented if therapies are tailored to disrupt both routes at once.

For the oncology biopharma ecosystem, the result magnifies the importance of companion diagnostics and precise patient stratification. If a tumor’s survival circuitry can switch to the backup pathway, a biomarker panel that detects this readiness could inform whether a patient should receive a combination upfront rather than a single agent. And while the prospect is appealing, it comes with caveats: combining agents often raises the bar for safety and tolerability, demanding rigorous dose-finding and monitoring protocols.

Two practitioner takeaways stand out. First, biomarker-driven trial design will be essential to identify which tumors most rely on the backup pathway and would benefit from combination therapy. Second, developers must plan for added toxicity and complex pharmacodynamics when pairing inhibitors, plus robust real-world endpoints beyond initial response rates to gauge meaningful, durable benefit.

In short, the MIT result is a reminder that cancer’s signaling networks are not a single-thread story. They’re a web, with backup routes that can undermine even promising drugs. The path forward is not simply more potent drugs, but smarter orchestration: identify the tumors that need a two-pronged attack, and design regimens that hit both routes without overwhelming patients.