ABSTRACT Several studies demonstrated that daily alcohol consumption (~1g) increases breast cancer risk by ~20% in women by promoting estrogen and other hormones, DNA damage as well as cell proliferation and epithelial– mesenchymal transition. Receptor tyrosine-protein kinase 2 (ErbB2) is a transmembrane receptor with intrinsic tyrosine kinase activity that plays an important role in human malignancies providing an enhanced response to ethanol-stimulated cell growth, invasion and migration. Normally, 20 ~ 30% of breast cancer with poor prognosis and relapse are ErbB2-positive. Alcohol appears to control signaling parameters of both upstream and downstream ErbB2 targets. Despite the efficacy of ErbB2-targeting therapy for breast cancer, only a fraction of patients responds successfully to therapy, while risks of recurrence are still high. The StAR related lipid transfer protein 10 (StarD10) is a phospho protein lipid transporter that shuttle the molecules from the endoplasmic reticulum through the plasma membrane and regulates its integrity, well-known to be altered during cell cancer transformation. StarD10 was described to be co-expressed with ErbB2 in 35% of primary human breast cancers, thereby supporting its role in deregulated cell growth and tumorigenesis. We recently reported that ethanol administration enhances StarD10 expression via ErbB2-induced p65 in MMTV-neu transgenic mice and in breast cancer cell lines. Also, StarD10 overexpression increases membrane fluidity, while ethanol promotes its dephosphorylation at tyrosine 288 residue (T288) points towards a lipid-related phenomenon. This proposal tests the novel hypothesis that ethanol induces changes in StarD10 biological activity, which may play a key role in breast cellular homeostasis thereby regulating malignancy/aggressiveness defining a novel therapeutic target. Aim 1: Examine how phosphorylation of StarD10 influences its biological function upon alcohol exposure in breast cancer. We will define the role of StarD10 phosphorylation (pStarD10) in ethanol-induced in breast cancer using CRISPR–Cas9 technology for the precise genome editing of pStarD10 at threonine 288 residue impacting on its lipid transporter activity, thus on plasma membrane fluidity. Aim 2: Examine the role of ethanol-induced StarD10 activity in ErbB2 signaling. We will investigate whether the phospho status of StarD10 influences ErbB2 activity and downstream pathways by its role as lipid transporter. Also, ErbB2 nuclear translocation will be examine. Aim 3: Examine the effects of StarD10 L260 gene editing in ethanol-fed breast cancer model. We will investigate whether protein phosphatase 2A (PP2A) activates StarD10 by dephosphorylating T288 residue inhibits aggressiveness in vitro ethanol-treated human breast cancer organoids (hBr-OUs) and in vivo hBr-OUs transplanted mouse model when the PP2A is mutated by CRISPR technology. Successful completion of these aims should enhance our knowledge of the complex interplay between the StarD10 phosphorylation and ErbB2 cell signaling ethanol-induced breast cancer, topics that are highly relevant to public health.

PROJECT NARRATIVE Chronic alcohol consumption is linked with an increased risk of breast cancer development and progression in women. We have found that ethanol administration causes changes in the phosphorylation status of StarD10, an essential lipid transporter, and it is associated with altered cell growth and malignancy. Our proposal aims to investigate how phospho StarD10 modifications under alcohol abuse can be controlled and may provide a therapeutic target for alcohol-induce breast cancer progression.