Contributed Talk

Decoding the biomechanome of colorectal cancer

Linda Decker¹, Dmitrii Olisov², Nikolai Schleußner³, Hendrik Wiethoff⁴, Henrik Nienhüser³, Thomas Moritz Pausch³, Jan Oliver Korbel², Alba Diz-Muñoz¹

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Increased tissue stiffness in solid tumours forms a barrier to the entry of immune cells, prevents the effective distribution of drugs in cancer tissue and promotes cancer invasiveness [1,2].
In colorectal cancer (CRC), stiffer tumours are associated with a poorer prognosis [3,4]. This stiffening is particularly prominent in liver metastases, which are the most common type of hematogenous CRC metastasis, and are correlated with reduced survival times and increased mortality [4,5].

The stiffness of tissue is mainly determined by the composition of the extracellular matrix (ECM), a fibrous network that not only provides structural support but is also involved in signalling. It is constantly turned over via the synthesis of components such as collagens and the secretion of matrix metalloproteases and other remodelling enzymes. During cancer progression, ECM secretion and modulation are dysregulated resulting in increased tissue stiffness.

Previous studies from our lab indicate the great potential that targeting tissue stiffness holds
for improving patient outcomes. The work from Shen et al. (2020) associates a group of blood
pressure medications with softer tissue and increased survival chances in CRC liver metastasis patients receiving one of these drugs [4]. As a possible mechanism, Shen et al. showed that those medications reduce the collagen-contracting abilities of patient-derived cells from the tumour microenvironment, the metastases-associated fibroblasts (MAFs)[4].

MAFs or cancer-associated fibroblasts (CAFs) are the main drivers of tissue stiffening in cancer. They are located in the stroma of tumours where they excessively remodel and contract the ECM. The term CAF encompasses a plethora of sub-types which can be associated with both anti-tumour and tumour-promoting effects [2,6]. A consensus classification of CAF sub-types, as well as thorough insights into their mechanisms of action, is still lacking. This highlights the need for unbiased approaches with spatial resolution which can resolve the stiffness contributions of different CAF sub-populations.

This study aims to identify new molecular players involved in the establishment, modulation, and regulation of tissue mechanical properties: the biomechanome. Using the novel combination of atomic force microscopy and spatial transcriptomics in adjacent cryo-sections, we are mapping the ECM stiffness of human CRC liver metastases and spatially correlating these data to their local transcriptome. To date, we have successfully established the experimental and data registration pipelines and obtained the correlated stiffness and transcription maps of 8 samples. We detected large inter- and intra-patient variability in mechanical properties as well as in gene expression. To corroborate these observations, we are currently increasing our data set to 20 samples as well as 3 healthy liver controls as reference. Besides classic differential expression analysis between soft and stiff areas, we are training a random forest regression model on our data that predicts tissue stiffness based on gene expression. The activity of several genes that is most predictive of the stiffness is potentially linked to stiffness modulation.

As a next step, we will validate the stiffness-modulating abilities of our top candidates in patient-derived MAFs. We will downregulate the target genes via siRNA-mediated knockdowns and evaluate the ability of knockdown cells to remodel an artificial ECM. We will complement this analysis with direct mechanical readouts such as atomic force and Brillouin microscopy. Finally, the selected genes will be correlated with the clinical outcomes of our patient cohort and published datasets. We envision that stiffness-modulating genes will serve as new targets for mechanomedicines.