Deciphering Invasive Growth Programs of Cancer: Implications for Prognosis and Treatment

This thesis focuses on elucidating the biological processes that drive invasive cancer. Chapter 1 presents a comprehensive overview of diverse biological processes required for invasion initiation and progression, including cytoskeletal rearrangement, growth factor receptor dynamics and ECM reorganization. Chapter 2 provides the foundations for using HPV-negative HNSCC patient derived organoid models as a clinical proxy to investigate spatial expression profiles of keratins during invasion. Furthermore, we developed a prognostic 5-tier spatial expression scoring system for Keratins, which identified that a combination of K14 homogenous expression and loss of K13 at the tumor invasive front correlates with poor survival. In Chapter 3 we used single cell mRNA sequencing to decipher the invasive transcriptional programs in HNSCC. Differential expression analysis reveals a YAP-centred transcriptional program that governs invasion. In particular, collective invasion is characterized by increased nuclear translocation of YAP and upregulation of its transcriptional targets. Pathway ontology analyses showed that single cell invasion is characterized by an immune migratory pathway, while collective invasion features upregulation of adhesion and migratory effectors. Lastly, we demonstrate the prognostic utility of the collective signature in HNSCC and other major solid cancer types. Chapter 4 focuses on patient derived breast cancer organoids and mouse mammary carcinoma models to underpin leader cell properties during collective invasion. We show that biochemical interaction of specific basal-like leader cells with Collagen type-I fibres underpin transduction of mechanical cues through YAP in order to drive an invasive leader cell program. Subsequent protrusion formation and upregulation of ECM remodelling components promote Collagen fibre alignment, further perpetuating YAP activity to generate a feed-forward loop that amplifies collective invasion. In Chapter 5, Collagen associated mechanical, chemical, and structural cues that control breast cancer invasion and progression are uncoupled to explain how local ECM stiffness and bundling control invasion. The data in this chapter show that increased Collagen type-I fibre thickness promotes collective and single cell invasion, while systemic Collagen stiffening impairs collective invasion. Moreover, Lysyl oxidase-like 3 (Loxl3) production at the invasive front promotes invasion through Collagen stiffness and alignment at the invasive front. Finally, in Chapter 6, we identify FER kinase as a key and central player that drives invasive growth through growth factor receptor activation in HNSCC. We demonstrate that FER correlates with poor survival outcome in HNSCC patients. High FER expression is essential for cancer cell invasion through dynamic endocytic recycling of both EGFR and MET receptors. We show that FER depletion through genetic knockdown or PROteolysis-TArgeting Chimera (PROTAC) in PDO-based xenograft preclinical mouse models diminishes invasive growth and metastasis.