Organotypic models as powerful tools to study the crosstalk between OC and thetumor microenvironment
The interaction between a tumor and its surrounding microenvironment shapes the behavior of cancer cells and plays a key role in many processes such as dissemination, acquisition of stem-like properties and chemoresistance.
Thus, in order to gain a better understanding of ovarian cancer (OC) biology, our group has generated a platform of organotypic models, in which tumor cells are co-cultured with patient-derived mesothelial cells and fibroblasts, mimicking the peritoneal microenvironment that is a primary site of OC dissemination.
In the past few years, we leveraged these models to document the remarkable impact of the TME on the transcriptional activity of OC cells, which also highlighted the ability of organotypic cultures to unveil novel mediators of the crosstalk with the TME and also drivers of cancer stemness.
Our group is now exploiting these organotypic models in several projects, in which we apply cutting-edge technologies (i.e. CRISPR screening, single-cell RNAseq) and multi-omic profiling to address clinically relevant questions, such as the mechanisms of response/resistance to standard therapies (platinum-based chemotherapy, PARP inhibitors, etc.), the biology of different OC subtypes, and the effect of the TME on OCSC pathophysiology.
Matrix Gla Protein: a TME-induced driver of stemness
Matrix Gla Protein (MGP) has been extensively characterized as a vitamin K-dependent factor that prevents calcification in vessels, cartilage and kidney. While it has been initially described as an extracellular and matrix- associated protein, MGP has also been found aberrantly expressed in different cancer types, including OC.
Yet, the role of MGP in cancer progression and the underlying biological mechanisms remained elusive. We identified MGP as a marker and a driver of OCSC and showed not only that its expression is induced by the peritoneal microenvironment, but also the MGP is a key player in TME-induced OC stemness.
We are now further investigating the role of MGP in the OC-TME crosstalk, with a focus on response to chemotherapy; we are also exploring the molecular mechanisms that underlie all these novel roles of MGP following various experimental approaches, such as mass spectrometry-based interactomics to identify MGP molecular partners and high-throughput drug screening to interfere with MGP-mediated signaling.
The role of L1CAM in OCSC-TME crosstalk
L1CAM is a cell-surface adhesion molecule originally identified and characterized in the central nervous system. We and other have subsequently documented the expression of L1CAM also in other non-neural tissues. Moreover, L1CAM is aberrantly expressed in several tumor types, where it contributes to invasion and metastasis.
In the context of OC, after implicating L1CAM in tumor invasion and dissemination, we have uncovered the upregulation of L1CAM in OCSC with a cell-autonomous role in their self-renewal and tumorigenic properties, through the activation of FGFR1/SRC/STAT3 axis. We have also discovered that L1CAM is frequently detected in the vasculature of various solid tumors, including OC, but not in normal vessels.
Subsequent studies revealed that the endothelial cells (EC) in OC vessels express high levels of a novel alternatively spliced isoform of L1CAM, termed L1-DTM, that lacks the transmembrane domain (yet maintaining the cytoplasmic tail) and, hence, acts as a secreted, soluble molecule, unlike the canonical full-length L1CAM that instead is membrane-bound.
We have subsequently obtained compelling evidence that EC-derived L1-DTM acts as a novel angiocrine molecule that orchestrate the pathophysiology of OCSC, thus emerging as a key factor in the interplay between the vascular TME and the OC stemness. We are currently exploring the non-cell-autonomous function of endothelial L1-DTM in OCSC and elucidating the underlying molecular mechanisms, building on several cutting-edge technologies (transcriptomics, mass spectrometry-based interactomics, etc.) and on a range of innovative experimental models ranging from orthotopic tumors in syngeneic mice to in vitro perivascular niche-on-chips.