Theocharous, M. | bioRxiv Science

bioRxiv2024

Ribosomal Biogenesis Hyperactivation and ErbB signalling Mediated Network Rewiring Causes Adaptive Resistance to FGFR2 Inhibition

Fibroblast Growth Factor Receptor 2 inhibition presents a promising therapeutic approach for restraining the growth and survival of cancer cells, particularly in breast tumours. However, the emergence of resistance to FGFR2 inhibitors like PD173074 highlights the importance of understanding the molecular mechanisms driving resistance and identifying effective therapeutic strategies. In this study, we employed temporal quantitative proteomics and phosphoproteomics, complemented by computational clustering, PTM-SEA analysis, and kinase activity prediction, to monitor the response of MFM223 triple negative breast cancer cells to FGFR2 inhibition. Strikingly, we observed a marked enrichment of ribosome biogenesis function modules immediately following treatment, a phenomenon not observed with other inhibitors. Additionally, we discovered that CX-5461, an RNA polymerase I inhibitor, synergistically enhanced the growth inhibition induced by PD173074, mechanistically attributed to its significant suppression of rDNA transcription stimulated by PD173074. Moreover, our phosphoproteomics dynamic profiling identified the clustering of kinases within MAPK and ErbB signalling pathways, indicative of their reactivation in response to FGFR2 inhibition. Experimentally validating this finding, we observed a notable rebound in phosphorylation levels of key kinases such as ERK1/2 and ErbB3, and demonstrated a substantial synergistic effect of PD173074 in combination with Trametinib, a MEK inhibitor, in suppressing cancer cell growth. Collectively, our findings provide critical insights into the network rewiring triggered by FGFR2 inhibition and offer a foundation for the rational design of combinatorial therapeutic strategies to overcome resistance mechanisms associated with FGFR2 inhibitors.

cancer biology↗

bioRxiv2022

Systems modelling of TGF-β/Hippo signalling crosstalk uncovers molecular switches that coordinate YAP transcriptional complexes

The Hippo pathway is an evolutionarily conserved signaling network that integrates diverse cues to regulate cell fate and organ homeostasis. The central downstream pathway protein is the transcriptional co-activator Yes-associated protein (YAP). Although capable of inducing gene transcription, YAP cannot bind DNA directly. Instead, it mediates transcriptional activity through interaction with distinct DNA-binding transcriptional factors (TFs), including TEAD, SMAD, and p73, to form active and functionally opposing transcriptional complexes. Growing evidence in mammals demonstrates that YAP has a dual role and can either promote cell proliferation or apoptosis, which underpin its ability to function as both an oncogene or a tumour suppressor depending on the specific context. However, the mechanisms by which YAP coordinates its distinct transcriptional complexes and mediates context-dependent function remain poorly defined. This is in part due to the lack of systems-level studies that can decrypt the complexities of upstream signalling pathways and their crosstalk, which together dictate the transcriptional regulation at the YAP level. Here, we undertake an integrative systems-based approach combining computational network modelling and experimental studies to interrogate the dynamic formation of and transition between the YAP-SMAD and YAP-p73 transcriptional complexes, which control proliferative and apoptotic gene expression, respectively. We developed a new experimentally-validated mathematical model of the TGF-{beta}/Hippo signalling crosstalk and used this model to elucidate dynamic network behaviour. Our integrative studies uncovered previously unknown molecular switches that control the YAP-SMAD/p73 complexes in an on/off, switch-like manner. RASSF1A and ITCH were identified as major regulators of the switches, whereby a graded increase in ITCH expression can trigger YAP to abruptly switch from binding p73 to SMAD, swiftly promoting proliferative gene expression. Further, adjusting the model to reflect cell type-specific protein expression profiles using both in-house and publicly available experimental data enabled us to study the YAP switches under diverse and varied cellular contexts. Overall, our studies provide a new quantitative and systems-level understanding of the dynamic regulation of functionally opposing YAP transcriptional complexes in mammalian cells.

cell biology↗