Institute of Biomedical and Biomolecular Science

Sassan Hafizi

Our research primarily focuses on the biology and pathological significance of the Tensin family of intracellular proteins, as well as the Gas6/Axl ligand-receptor system.

For further details and publication history please see my staff profile

Our current laboratory research

Tensin family of intracellular proteins

These are multi-modular intracellular proteins that house C terminal SH2-PTB tandem domains, as well as, in Tensins1-3, a phosphatase domain homologous to that of the tumour suppressor PTEN.

Our lab cloned two variants of the human Tensin2 gene (TENC1), and we observed that the protein displayed similar phenotypic and signalling effects on cells as PTEN. We have also observed all four Tensins to be down-regulated in expression in human kidney cancer.

Moreover, these proteins have the additional properties of binding to growth factor receptors (such as Axl), integrins and tumour suppressors (such as DLC1). Through these interactions, the Tensins appear to coordinate amongst themselves the cytoskeletal architecture that underlies the potential for tumour cells to become motile and metastasise, while also potentially negatively regulating growth/survival signalling pathways. The goal of our lab is to uncover the role the Tensin protein family in tumour progression and spread, in particular focussing on kidney cancer, for which we have excellent collaborative links. To this end, we are characterising each Tensin for cellular effects, downstream signalling, protein/membrane interactions, enzymatic activity, molecular structure, and mechanisms behind altered expression in tumours.

The Tensin protein family and their domain organisations

The Gas6/Axl system

Axl is a receptor tyrosine kinase of the same superfamily as the receptors for other growth factors EGF and PDGF. However, Axl has some molecular features not shared by other molecules that enable it to be oncogenic, and particularly pro-metastatic, in a unique way. Gas6 is a growth/survival factor that is the ligand for Axl, and is relatively unique in being a vitamin K-dependent protein, which is a property normally associated with blood coagulation factors. We have uncovered a number of protein interactions with Axl inside the cell, which may relay the effects of Gas6 binding and activation.

Both Gas6 and Axl are present widely throughout the human body, and Axl has been shown to be overexpressed in many different cancers including the kidney and brain, which are tumours we are particularly working on. We have for a number of years been characterising the Gas6/Axl pathway, both in terms of its normal structure-function relationships, as well its altered expression/activity in diseases such as kidney cancer. We are currently further probing the effects of Gas6/Axl signalling on phenotypic characteristics including proliferation, adhesion and migration and on intracellular signal transduction. Recently, we have also turned out attention to the potential of the Gas6/Axl pathway to drive cell migration and invasion of glioma cells. Furthermore, we are also investigating novel selective Axl inhibition agents as potential anticancer therapies.

Gas6/protein S-Axl interaction on the cell surface leads to signalling for survival and/or growth