Scientists find the genetic switch that makes pancreatic cancer resist chemotherapy

The study, published in the Journal of Clinical Investigation, explains how this switch operates at a molecular level. The results suggest that pairing targeted therapies with standard chemotherapy may improve outcomes for patients whose tumors no longer respond to treatment.

Why Pancreatic Cancer Is So Difficult to Treat

Pancreatic cancer is one of the deadliest cancers worldwide. In Singapore, it ranks as the ninth most common cancer but the fourth leading cause of cancer related death. Because symptoms often appear late and current treatments have limited impact, most patients depend on chemotherapy, which typically provides only modest benefit.

Over the past decade, scientists have identified two main molecular subtypes of pancreatic cancer, classical and basal. Tumors in the classical subtype tend to be more organized at the cellular level, and patients with this form are more likely to respond to treatment. In contrast, basal subtype tumors are more disorganized and aggressive, and they are often resistant to chemotherapy.

Importantly, pancreatic cancer cells are not fixed in one subtype. They can shift between these states, moving from a more treatable form to a more resistant one. This flexibility is known as cancer cell plasticity.

The Role of GATA6 in Tumor Behavior

The research team focused on a gene called GATA6, which helps maintain pancreatic cancer cells in the more structured and less aggressive classical state. When GATA6 levels are high, tumors tend to grow in a more organized way and are more likely to respond to chemotherapy. When GATA6 levels fall, cells lose that structure, become more aggressive, and are harder to treat.

Professor David Virshup of Duke-NUS's Programme in Cancer & Stem Cell Biology, the study's lead author, said:

"We have known that pancreatic cancer cells can switch between these two states. What we didn't understand was the mechanism driving that switch. By identifying the pathway that suppresses GATA6, we now have a clearer picture of how tumors become resistant -- and potentially how to reverse that process."

KRAS and ERK Pathway Drive the Switch

The researchers traced the switch to a chain of signals inside pancreatic cancer cells. A gene called KRAS, which is mutated in nearly all pancreatic cancers, sends constant growth signals that drive tumor development. KRAS passes these signals through a partner protein known as ERK, which relays the instructions further inside the cell.

When the ERK pathway becomes highly active, it protects another protein that interferes with the production of GATA6. As GATA6 levels drop, cancer cells lose their organized structure, shift toward the more aggressive basal state, and become much less responsive to chemotherapy.

Using genetic screening, molecular analysis in cancer cells, and drug treatments, the team demonstrated that blocking the KRAS and ERK pathway lifts this suppression. When that happens, GATA6 levels rise again. The cancer cells then shift back toward the more organized state and regain sensitivity to chemotherapy.

Combination Therapy Shows Stronger Effects

The study also found that higher levels of GATA6 on their own made pancreatic cancer cells more responsive to treatment. When drugs that inhibit the KRAS and ERK pathway were combined with standard chemotherapy, the anti cancer effects were stronger than with either approach alone. However, this enhanced benefit occurred only when GATA6 was present, highlighting its central role in determining which patients might benefit most from combination therapy.

These findings help clarify why patients with higher GATA6 levels often respond better to certain chemotherapy regimens. They also provide a scientific foundation for ongoing clinical trials that are testing new treatments aimed at KRAS and related pathways.

Professor Lok Sheemei, Duke-NUS' Interim Vice-Dean for Research, said:

"Pancreatic cancer remains one of the toughest cancers to treat. These findings provide a mechanistic explanation for why tumors respond poorly to chemotherapy and offers a rational strategy for combining targeted therapies with existing drugs."

Broader Implications for Other KRAS Driven Cancers

The implications may extend beyond pancreatic cancer. Many other cancers fueled by KRAS mutations show similar shifts in cell behavior and treatment response. Understanding how cancer cells transition between different states could help researchers address therapy resistance in additional cancer types.

Professor Patrick Tan, Dean and Provost's Chair in Cancer and Stem Cell Biology at Duke-NUS, commented:

"This work demonstrates how basic science can uncover actionable insights into treatment resistance. Understanding how cancer cells switch states gives us a more strategic way to design combination treatments."

Duke-NUS Medical School is internationally recognized for its leadership in medical education and biomedical research, combining fundamental discoveries with translational expertise to improve health outcomes in Singapore and beyond.