IDIBELLfellows: Pedro Fuentes & Sara Montserrat

LARP1-Mediated Drug Tolerance in Colorectal Cancer: A Non-Genetic Mechanism Underlying Chemoresistance and Tumor Relapse
Pedro Fuentes – Cancer Metabolism group
Non-genetic processes driving drug tolerance present a significant challenge in cancer therapy. Drug-tolerant persister (DTP) cells, which emerge during chemotherapy and are largely influenced by mTOR signaling, drive non-genetic heterogeneity and offer a therapeutic opportunity before the emergence of irreversible mutation-driven resistance.
In the context of mTOR inhibition, our group discovered that the 40S-LARP1 complex protects the translational program for ribosome biogenesis and protein synthesis under adverse conditions, enabling tumor cells to resume proliferation once growth conditions are restored. In colorectal cancer (CRC) models, we demonstrated that LARP1 expression becomes critical in maintaining anabolic potential only under inhibitory proliferative signals, particularly through mTOR inhibition.
CRC poses a major therapeutic challenge due to its high incidence and development of chemoresistance. First-line treatments, including 5-FluoroUracil (5-FU) combined with Oxaliplatin or Irinotecan, reduce tumor burden, but recurrence is common, ranging from 5-10% in stage I to 60-80% in stage IV.
This study investigates LARP1’s role in drug tolerance and tumor proliferation in CRC spheroids treated with 5-FU. Using advanced experimental approaches including 3D spheroid models, polysome profiling, fluorescence-activated cell sorting (FACS) analysis, and CRISPR-mediated genetic modification of cells, we demonstrate that LARP1 is crucial for recovery after 5-FU treatment. Spheroids lacking LARP1 exhibit impaired regrowth, highlighting its role in drug resistance. The reversible phenotype observed across three treatment-recovery cycles suggests that DTP cells only arise after 5-FU exposure through non-genetic adaptation. Additionally, xenotransplantation experiments in mice confirm LARP1’s critical role in tumor growth, facilitating cancer cell survival under therapeutic stress.

Analyzing the effect of RhoA inhibition in the epigenome and the transcriptome of aged hematopoietic stem cells
Sara Montserrat – Stem cell aging group
Cells are exposed to mechanical forces, both internal and external, and the nucleus can act as a mechanosensor and generate a response. RhoA is one of the main proteins participating in this response and it is necessary for hematopoietic stem cells (HSCs) to survive nuclear stretching. RhoA activity increases with aging in HSCs and its inhibition can restore H3K9me2 at heterochromatin and improve the function of aged HSCs after transplantation. To investigate the changes that RhoA inhibition (Ri) could be inducing in the epigenome and the transcriptome of aged HSCs, we performed bulk ATAC-seq and bulk RNA-seq of young, aged and aged+Ri HSCs. We found that Ri restored the accessibility/expression of some repetitive elements and downregulated pathways related to inflammation and the immune response. We also found that several genes of the Klf family of transcription factors (like Klf4, Klf2 and Klf6) were overexpressed in the aged HSCs treated with Ri and their DNA binding-motifs were more accessible. To gain further insight into the effects of the Ri treatment, we performed scRNA-seq of young, aged and aged+Ri hematopoietic stem and progenitor cells (also known as LSKs). We detected again an increase in the expression of Klfs, more prominent in the HSC cluster and confirmed the increased activity of these transcription factors by using the tool SCENIC (Aibar et al 2017). We finally saw an increase in a signature for hemogenic precursors in aged+Ri HSCs, indicating a possible reprogramming of these cells.