Role of flightless I in cancer growth and metastasis
Creators: name: Muhamad Zakuan, Noraina
Publisher: name: RMIT University
Year: 2024
Subjects: classificationCode: 321101
subject: Cancer cell biology
classificationCode: 321108
subject: Molecular targets
classificationCode: 321199
subject: Oncology and carcinogenesis not elsewhere classified

description: The aim of this project was to investigate the role of the Flightless I (FliI) protein in tumour growth and metastasis in vitro and in vivo using cultured colon cancer cells and a mouse colon cancer model. FliI is a member of the actin-remodelling protein family, which consists of gelsolin, adseverin, capG, villin and supervillin family members, which play important roles in cellular motility, contraction and adhesion. Several studies have investigated the function of FliI and its mechanism of action in both in vitro and in vivo models of wound healing in mouse skin. These studies showed that knockdown of FliI improved wound healing via increased cell proliferation, epithelial cell migration and enhanced wound closure, while also resulting in reduced scarring and inflammation. In contrast, overexpression of FliI caused impaired wound healing with larger, fewer closed wounds, reduced cellular proliferation and delayed epithelial migration, as well as excessive scarring.<br><br>Since there are parallels between the wound healing/scarring process and cancer progression, the aim of this study was to investigate the role of Flil in cancer growth and spread. Recently it has been shown that FliI expression also correlated with increased tumour growth in a mouse model of squamous cell carcinoma, while FliI inhibition using a neutralising antibody reduced tumour growth and invasion in this model. The FliI protein itself has been shown to be both localised intracellularly and also secreted; therefore, we have studied tumour growth both in mice with reduced FliI expression (FliI heterozygous knockout +/− mice) and also in wild type (WT) mice injected with cancer cells that have FliI knockdown using siRNA. In vitro, FliI expression levels were found to have significant effects on cell migration, cell proliferation, cell adhesion and invasiveness. Knockdown of FliI increased cell motility and proliferation, and was found to increase cell adhesion via upregulation of focal adhesion (FA) proteins, while reducing FliI expression greatly inhibited cellular invasion associated with reduced expression of an invadopodia marker. In vivo, colon cancer cells showed decreased spread to form fewer lung metastases in mice with reduced FliI expression (FliI heterozygous mice).<br><br>This suggests that host FliI expression levels can regulate tumour growth, possibly through an effect on tumour stromal cell behaviour. Interestingly, knockdown of FliI using siRNA also resulted in smaller primary tumours in mice, suggesting FliI expression in cancer cells could influence tumour growth in this model as well. In vitro, FliI expression correlated with decreased adhesion and increased invasion, suggesting FliI may play a role in tumour progression via effects on cell adhesion and invasion, potentially via effects on invadopodia formation. These findings suggest that FliI inhibition in both stromal and cancer cells may be a promising target for limiting tumour growth and spread. In addition, administration of a FliI-neutralising antibody (FnAB) showed potential for reducing tumour progression in metastatic models and reducing tumour spheroid invasion in vitro. Overall, the results suggest FliI may be a promising target for inhibiting tumour growth and metastasis.<br><br>The significance of this study is that FliI has been shown to play a role in mediating cellular functions which are important in tumour progression. FliI expression increased cellular invasion, possibly via an invadopodia mechanism correlated with increased cortactin expression. FliI expression has also been shown to influence tumour growth and spread in murine colon cancer models, while FliI inhibition either in the host or in cancer cells reduced tumour progression and metastasis. Importantly, this study demonstrates that the inhibition of FliI expression intracellularly and within hosts could modify the tumour microenvironment, thus reducing tumour growth. This present study also serves as a preliminary finding on the administration of FnAB to potentially reduce tumour growth and spread in animal models, which indicates that FliI could be a potential target for cancer therapy.