Patients with colorectal cancer have long relied on 5-fluorouracil, one of the most widely used chemotherapy drugs in cancer treatment, yet tumors frequently develop resistance—adapting to the drug and regrowing despite continued treatment. Now, researchers led by Dr. Hyun-Soo Cho at the Stem Cell Convergence Research Center of the Korea Research Institute of Bioscience and Biotechnology (KRIBB) have identified the molecular culprit behind this resistance and discovered a way to reverse it.
The breakthrough hinges on a protein called EHMT2, which controls how cancer cells regulate their genes. In a study published in Signal Transduction and Targeted Therapy, Dr. Cho's team—working with Professor Geun Heo of Kyungpook National University—showed that cancer cells exposed repeatedly to 5-FU dramatically increase their EHMT2 activity as a survival strategy. When the researchers analyzed patient data, they found a stark correlation: patients with elevated EHMT2 showed poorer responses to chemotherapy and lower survival rates.
The discovery emerged from elegant laboratory work. The team grew colorectal cancer cells that had survived repeated chemotherapy exposure and compared them to nonresistant cells. The resistant cells had markedly higher EHMT2 activity. To test whether this protein truly drives resistance, the researchers suppressed EHMT2 in resistant cancer cells—and the cells suddenly regained sensitivity to 5-FU, leading to increased cell death and reduced proliferation. When they artificially boosted EHMT2 in nonresistant cells, those cells became harder to kill with chemotherapy. The logic was clear: EHMT2 functions as a master switch for drug resistance.
What makes this finding clinically significant is that the researchers didn't stop at laboratory dishes. They tested their approach in patient-derived tumor organoids and animal models, combining 5-FU with an EHMT2 inhibitor. Tumors that had previously resisted chemotherapy shrank substantially. Dr. Cho emphasized the implication: "Targeting EHMT2 may provide a new therapeutic approach to overcoming drug resistance and enhancing the efficacy of existing anticancer treatments."
This matters because oncologists wouldn't need to invent entirely new drugs. Instead, by pairing EHMT2 inhibitors with the established chemotherapy regimens already in use, physicians could potentially restore sensitivity in resistant tumors, effectively breathing new life into treatments that have already helped countless patients. For people whose cancers have stopped responding to standard therapy, this opens a tangible pathway forward.
The potential extends well beyond colorectal cancer. The 5-FU drug is also used to treat gastric, pancreatic, and breast cancers, all of which may suffer from similar EHMT2-driven resistance. If the mechanism holds across these cancers, the findings could reshape how clinicians approach chemotherapy resistance across multiple disease types.
The work represents a shift in thinking about cancer treatment failure—rather than viewing resistance as an insurmountable obstacle, researchers are identifying its biological underpinnings and learning to dismantle them. For patients facing cancer recurrence after chemotherapy, and for the clinicians treating them, this discovery offers something rare: the prospect of making existing, familiar medicines work again.