Lysyl oxidase-like 2 (LOXL2) is anticipated to be a promising novel therapeutic target in basal- like breast cancers, because it is highly upregulated in these cancer cells and tissues, and because inhibition of the production of LOXL2 by shRNAs or treatment with its specific antibody have been shown to retard tumor progression and metastasis/invasion in tissue culture and in animal models. LOXL2 belongs to the lysyl oxidase (LOX) family, which consists of lysine tyrosylquinone (LTQ)-dependent copper amine oxidases. LOXL2 is generally considered to catalyze ECM stiffening by its amine oxidase activity. However, intracellular functions of LOXL2 have also recently been proposed. To date, there are no structures for LOXL2 or any member of the LOX family, and very limited fundamental biochemical and biological study of LOXL2 has been conducted. We have discovered that nuclear (unglycosylated) LOXL2 induces epithelial- to-mesenchymal transition (EMT, the first step of metastasis) of breast cancer cells and promotes cell proliferation and invasion much more effectively than secreted (N-glycosylated) LOXL2 does in vitro. We also found that secreted LOXL2 undergoes nuclear-translocation to induce EMT. Our central hypothesis is that unglycosylated LOXL2 localizes to the nucleus, and there induces EMT and invasion by stabilizing Snail1 transcription factor in an amine oxidase activity-dependent fashion. Therefore, we wish to develop strategies to inhibit the production, nuclear accumulation, and/or activity of LOXL2, which could potentially be developed into a targeted therapy for cancers expressing nuclear LOXL2. In this proposal we will define the post-translational modifications (PTMs) of LOXL2 and decipher their roles in directing distinct molecular functions of LOXL2 in breast cancer metastasis/invasion. Successful completion of the proposed studies will provide the first substantial insight into the structure- function correlation of LOXL2. Ultimately, the success of this study will inform the design of targeted therapies for a subtype of basal-like breast cancers expressing elevated levels of nuclear LOXL2.
The present average five-year survival rate of female invasive breast cancer patients is 90%;however, that of distant-stage patients plummets to only 24%. Because proper treatment can delay tumor progression and prolong patients'lives, it is critically important to identify therapeutic targets and understand their molecular mechanisms, then use this knowledge to develop drugs and methods to block their actions. In this application we focus on lysyl oxidase-like 2, a protein that is highly expressed in metastatic breast cancer cells and tissues. We plan to dissect and understand the relationships between the structures of various forms of LOXL2 and their corresponding molecular contributions to breast cancer metastasis/invasion. The results of this study will greatly aid the design of strategies to inhibit LOXL2 and slow the progression of invasive breast cancer.