Deep inside every cell, DNA is wrapped around proteins called histones, like thread on a spool—and how tightly that thread winds or unwinds determines which genes stay silent and which come to life. For decades, cancer researchers believed they had figured out one crucial lever: histone deacetylase enzymes, or HDACs, which remove chemical acetyl groups from histones and drive tumor growth. Blocking these enzymes with drugs called HDAC inhibitors became a logical cancer strategy. But researchers at Baylor College of Medicine and collaborating institutions have just challenged that entire framework, suggesting the story is far more complicated than anyone realized.
The research, led by Dr. Zheng Sun, an associate professor of medicine at Baylor's Dan L Duncan Comprehensive Cancer Center, overturns decades of assumptions. "The prevailing idea has been that increasing histone acetylation with HDAC inhibitors promotes beneficial gene expression changes that may slow cancer or lead to cancer cell death," Sun explains. "Yet, some findings do not support this idea."
Those inconsistencies nagged at Sun and his team. In some cancers, HDACs don't promote tumors at all—they actually suppress them. In other cases, HDAC inhibitors successfully increased histone acetylation but produced only modest changes in gene expression. Something didn't add up. To investigate, the researchers, including first author Dr. Chaitra Rai, applied unbiased computational approaches to examine the relationship between HDACs and various solid tumors, testing their hypotheses in multiple mouse models where HDAC inhibitors are currently used in clinical trials.
The results were striking. Bioinformatics analyses revealed that HDACs are not universally linked to cancer growth—different types of HDACs or their levels didn't consistently correlate with most cancers or patient survival rates. More dramatically, when researchers tested the HDAC inhibitor FK228 in mice, they found its anticancer effects were independent of its ability to inhibit HDACs at all. Even more telling: when the team engineered HDAC inhibitors that could no longer block those enzymes, the drugs retained most of their anticancer punch in living organisms.
The findings, published in Signal Transduction and Targeted Therapy, suggest a fundamental reconceptualization of how these drugs actually work. Rather than being single-target weapons aimed at HDAC enzymes, HDAC inhibitors may simultaneously interfere with multiple proteins—hitting pathways scientists have yet to fully map. "We propose that HDAC inhibitors may also interfere with other proteins and that targeting such proteins may suppress cancer," Sun said.
This insight carries real weight for patients. If researchers can identify the other molecular targets these drugs hit, they might design even more effective treatments, or understand why some patients respond to HDAC inhibitors while others don't. The work doesn't invalidate existing cancer therapies—it simply reveals they're far more complex tools than the original model suggested. In precision medicine, where understanding a drug's true mechanism can unlock better outcomes, that clarity matters enormously.
The next chapter belongs to the scientists now tasked with uncovering those hidden targets, turning assumptions into answers.