Microphthalmia-associated transcription factor (MITF) is critical in melanoma for the regulation of tumour architecture, three-dimensional extracellular matrix (ECM) scaffolding and cell cycle behaviour. Specifically, high MITF expression increases cell cycle homogeneity with an even distribution of proliferating tumour cells. Additionally, MITF negatively impacts the Rho-ROCK-myosin-contractility axis, changing cell-cell and cell-ECM interactions, creating a ‘sponge-like’ tumour. Conversely, low MITF increases cell cycle heterogeneity, with clusters of proliferating cells and clusters of G1-arrested cells and enforces denser 3D structures with greater solid stress. A holistic understanding of these phenotypic changes by MITF and the direction of cascading effects is not well understood. Specifically, whether observed cell cycle changes are directly affected by MITF intrinsically, causing ECM changes in the microenvironment or whether changes to the ECM by MITF extrinsically affect cell cycle behaviour. To assess this, key contributors to ECM modulation affected by MITF were identified and altered to observe resulting cell cycle effects. This project focuses on SERPINH1, Peroxidasin (PXDN), Apolipoprotein E (APOE) and Neprilysin as the key contributors to ECM modulation pathways. ROCK inhibition and external stress were also assessed. Our findings show evidence for an extrinsic effect by the ECM on cell cycle heterogeneity with great variability and inconsistency. External stress on 3D models however clearly displayed the expected effect on cell cycle heterogeneity aligning with previous findings. Continuous investigation into the interaction between cell-ECM crosstalk will further establish the involvement of MITF in melanoma intratumoural phenotypic heterogeneity and subsequently outline current limitations between patient treatment efficacy and tumorigenic behaviours.