Pancreatic tumors are not only biologically aggressive, they are physically protected. This study reveals how mechanical pressure within the tumor microenvironment activates survival pathways, reducing chemotherapy effectiveness, and highlights a promising strategy to overcome resistance.
A fibrotic fortress protecting pancreatic tumors
Pancreatic ductal adenocarcinoma (PDAC) is one of the most difficult cancers to treat. Even with aggressive therapies such as FOLFIRINOX, patient outcomes remain poor. One major reason is not only the biology of the tumor itself, but also the physical environment surrounding it.
Pancreatic tumors grow within a dense and fibrotic tumor microenvironment (TME). This stiff structure, rich in collagen and fibroblasts, creates strong mechanical pressure that compresses blood vessels and limits drug delivery. However, this pressure is not just a physical barrier. It can also directly influence how cancer cells behave.
In this study, Kalli and colleagues investigated whether mechanical compression activates autophagy, a survival mechanism that allows cells to recycle internal components under stress. They hypothesized that this process could make cancer cells more resistant to chemotherapy, and that combining mechanical stress relief with autophagy inhibition could improve treatment response.
Recreating tumor pressure in the laboratory
To explore this, researchers reproduced tumor-like pressure in the lab. Human pancreatic cancer cells (MIA PaCa-2 and PANC-1) were subjected to controlled compression, similar to what is observed in real tumors. These experiments were complemented by studies in mouse models.
The team then tested the effect of oxaliplatin, a key drug used in FOLFIRINOX. They also introduced two additional treatments: hydroxychloroquine (HCQ), which blocks autophagy, and losartan, a drug known to reduce tumor stiffness and mechanical stress.
To analyze cellular responses, they measured key protein markers of autophagy and apoptosis (such as LC3B, p62, and caspase-3) using immunoblotting. These signals were detected via chemiluminescence using the Alliance imaging system (Uvitec), enabling sensitive visualization and accurate quantification of protein expression changes. In parallel, tumor stiffness and blood flow were assessed using advanced imaging techniques such as shear wave elastography and contrast-enhanced ultrasound.
Mechanical stress activates a Cellular Survival Program
The results showed that mechanical compression strongly increases autophagy in pancreatic cancer cells. This means that cells activate a survival program to cope with stress.
At the same time, chemotherapy became less effective. Under compression, cancer cells showed reduced apoptosis, meaning fewer cells died in response to oxaliplatin. In simple terms, the physical pressure around the tumor helps cancer cells survive treatment.
However, when autophagy was blocked using hydroxychloroquine, the situation changed. Cancer cells became sensitive again to chemotherapy, even under compression.
The most effective results came from combining treatments. Losartan reduced tumor stiffness and improved blood flow, allowing better drug delivery. When combined with HCQ and oxaliplatin, this approach significantly slowed tumor growth in mouse models.
A new therapeutic paradigm: Targeting Both Physics and Biology
This study highlights an important concept: mechanical forces are not just passive obstacles but active contributors to chemotherapy resistance. By triggering autophagy, tumor pressure creates a protective environment for cancer cells.
These findings suggest a promising strategy: targeting both the physical properties of the tumor and the cellular mechanisms that support survival. Because hydroxychloroquine and losartan are already used in clinical practice, this combined approach could potentially be tested quickly in patients.
Further research is still needed to better understand how mechanical stress activates autophagy and to identify which patients may benefit most. However, this work clearly shows that improving cancer treatment may require not only targeting tumor cells, but also modifying the physical environment in which they evolve.
Results at a glance
More pictures from the Cancer Biophysics Laboratory
The following pictures where taken with our Alliance Q9 system by Tereza Andreou at the Cancer Biophysics Laboratory (University of Cyprus). Many thanks to her as well as Maria Kalli and all the team for their trust and for sharing their work with us.
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