Biology subjects

Malliri, A.

Publications and source records attributed to Malliri, A..

5 recordsLinked to original sources

bioRxiv2024

A stretchable and biomimetic polyurethane membrane for lung alveolar in vitro modelling

The lung alveolus constitutes a morphologically and mechanistically complex tissue that is constantly subjected to cyclic tension and exhibits unique elastic properties. Available materials used to mimic alveolar tissue often lack biomimicry and the mechanical properties required for cyclic tension. Here, we report a fully synthetic fibrous polyurethane scaffold that approximates tissue stiffness, is elastic under breathing simulations and supports long-term culture of alveolar epithelial-like cells. Using electrospinning a fibrous membrane of tuneable thickness, set fibre diameter and small pore size is prepared. When subjected to cyclic uniaxial tension the material retains its elasticity at both low and high frequency mimicking human and mouse breathing. Thanks to the small pore size, lung alveolar cells can be cultured on its apical surface forming an epithelial monolayer. This monolayer can be maintained long term (at least 15 days) and in an air-liquid interface. In the latter conditions, cells differentiate and exhibit expression of surfactant protein A, a constituent of the surfactant layer that plays a key role in lung physiology. Owing to its lung-mimicking characteristics, the electrospun membrane holds the potential to be adapted for breathing lung models.

bioengineering↗

bioRxiv2023

The PI3K-AKT-mTOR axis persists as a therapeutic dependency in KRASG12D-driven non-small cell lung cancer

IntroductionKRASG12C and KRASG12D inhibitors represent a major translational breakthrough for non-small cell lung cancer (NSCLC) and cancer in general by directly targeting its most mutated oncoprotein. However, resistance to these small molecules has highlighted the need for rational combination partners necessitating a critical understanding of signaling downstream of KRAS mutant isoforms. MethodsWe contrasted tumor development between KrasG12Cand KrasG12D genetically engineered mouse models (GEMMs). To corroborate findings and determine mutant subtype-specific dependencies, isogenic models of KrasG12C and KrasG12D initiation and adaptation were profiled by RNA sequencing. We also employed cell line models of established KRAS mutant NSCLC and determined therapeutic vulnerabilities through pharmacological inhibition. We analysed differences in survival outcomes for patients affected by advanced KRASG12C or KRASG12D-mutant NSCLC. ResultsKRASG12D exhibited higher potency in vivo, manifesting as more rapid lung tumor formation and reduced survival of KRASG12D GEMMs compared to KRASG12C. This increased potency, recapitulated in an isogenic initiation model, was associated with enhanced PI3K-AKT-mTOR signaling. However, KRASG12C oncogenicity and downstream pathway activation were comparable with KRASG12D at later stages of tumorigenesis in vitro and in vivo, consistent with similar clinical outcomes in patients. Despite this, established KRASG12D NSCLC models depended more on the PI3K-AKT-mTOR pathway, while KRASG12C models on the MAPK pathway. Specifically, KRASG12D inhibition was synergistically enhanced by AKT inhibition. ConclusionsOur data highlight a unique combination treatment vulnerability and suggest that patient selection strategies for combination approaches using direct KRAS inhibitors should be i) contextualised to individual RAS mutants, and ii) tailored to their downstream signaling.

cancer biology↗

bioRxiv2021

Ultraviolet light-induced collagen degradation inhibits melanoma invasion

Ultraviolet radiation (UVR) increases the incidence of cutaneous melanoma1-4. The ageing, sun-exposed dermis accumulates UVR damage5, and older patients develop more melanomas at UVR-exposed sites4,6,7. As fibroblasts are functionally heterogeneous and play key roles in the stromal contribution to cancer8,9, we asked whether UVR modifies dermal fibroblast function. Here we confirmed the expression of collagen-cleaving matrix metalloprotein-1 (MMP1) by UVR-damaged fibroblasts was persistently upregulated to reduce local levels of collagen 1 (COL1A1), and found dermal COL1A1 degradation by MMP1 decreased melanoma invasion. Conversely, we show inhibiting extracellular matrix degradation and MMP1 expression restored melanoma invasion to UVR damaged dermis. We confirmed in vitro findings in a cohort of primary cutaneous melanomas of aged humans, showing more cancer cells invade as single cells at the invasive front of melanomas expressing and depositing more collagen. We found collagen and single melanoma cell invasion are robust predictors of poor melanoma-specific survival. These data indicate melanomas arising over UVR-damaged, collagen-poor skin of the elderly are less invasive, and this reduced invasion improves survival. Consequently, although UVR increases tumour incidence, it delays primary melanoma invasion by degrading collagen. However, we show melanoma-associated fibroblasts can restore invasion in low-collagen primary tumours by increasing collagen synthesis. Finally, we demonstrate high COL1A1 gene expression is a biomarker of poor outcome across a broad range of primary cancers.

cancer biology↗

bioRxiv2020

The RAC1 activator Tiam1 regulates centriole duplication through controlling PLK4 levels

Centriole duplication is tightly controlled to maintain correct centriole number through the cell cycle. A key component of this control is the regulated degradation of PLK4, the master regulator of centriole duplication. Here we show that the Rac1 guanine nucleotide exchange factor (GEF) Tiam1 localises to centrosomes during S-phase, where it is required for maintenance of normal centriole number. Depletion of Tiam1 leads to an increase in centrosomal PLK4, centriole overduplication and ultimately to lagging chromosomes at anaphase and aneuploidy. The effects of Tiam1 depletion can be rescued by re-expression of wild-type Tiam1 and catalytically inactive (GEF*) Tiam1, but not by Tiam1 mutants unable to bind to the F-box protein {beta}TRCP, implying that Tiam1 regulates PLK4 levels through promoting {beta}TRCP-mediated degradation.

cell biology↗

bioRxiv2018

The interaction between the tumour suppressor Dlg1 and the MAGUK protein CASK is required for oriented cell division in mammalian epithelia

Oriented cell divisions are important for the formation of normal epithelial structures. Dlg1, a tumour suppressor, is required for oriented cell division in Drosophila epithelia and chick neuroepithelia, but how Dlg1 is localised to the membrane and its importance in mammalian epithelia are unknown. Here we show that Dlg1 is required in non-transformed mammalian epithelial cells for oriented cell divisions, and for normal lumen formation in 3D culture. We demonstrate that CASK, a membrane-associated scaffold, is the factor responsible for Dlg1 membrane localisation during spindle orientation, and thereby identify a new cellular function for CASK. We show that depletion of CASK leads to misoriented divisions in 3D, and to the formation of multilumen structures in cultured kidney and breast epithelial cells. Blocking the direct interaction between CASK and Dlg1 with an interfering peptide disrupts spindle orientation and causes multilumen formation. We further show that the Dlg1-CASK interaction is important for the membrane localisation of the canonical LGN-NuMA complex, required for attachment of the mitotic spindle to the membrane and its correct positioning, as well as for astral microtubule stability. Together these results establish the importance of the CASK-Dlg1 interaction in oriented cell division and epithelial integrity.

cell biology↗