One of the characteristic features of metastatic
breast cancer is increased cellular storage of neutral
lipid in cytoplasmic lipid droplets (
CLDs). CLD accumulation is associated with increased
cancer aggressiveness, suggesting
CLDs contribute to
metastasis. However, how
CLDs contribute to
metastasis is not clear.
CLDs are composed of a neutral
lipid core, a
phospholipid monolayer, and associated
proteins.
Proteins that associate with
CLDs regulate both cellular and CLD metabolism; however, the
proteome of
CLDs in metastatic
breast cancer and how these
proteins may contribute to
breast cancer progression is unknown. Therefore, the purpose of this study was to identify the
proteome and assess the characteristics of
CLDs in the MCF10CA1a human metastatic
breast cancer cell line. Utilizing shotgun proteomics, we identified over 1500
proteins involved in a variety of cellular processes in the isolated CLD fraction. Interestingly, unlike other cell lines such as adipocytes or enterocytes, the most enriched
protein categories were involved in cellular processes outside of lipid metabolism. For example, cell-cell adhesion was the most enriched category of
proteins identified, and many of these
proteins have been implicated in
breast cancer metastasis. In addition, we characterized CLD size and area in MCF10CA1a cells using transmission electron microscopy. Our results provide a hypothesis-generating list of potential players in
breast cancer progression and offers a new perspective on the role of
CLDs in
cancer.