Metabolic regulation of exosome biogenesis as a determinant of cancer cell metastasis.

Abstract. The studies outlined in this proposal focus on the mechanisms by which aggressive breast cancer
cells generate large numbers of exosomes with unique cargo, together with a total secretome that
significantly enhances their potential for metastatic spread. They are based on exciting developments in
the cancer biology field which show that exosomes, a major class of extracellular vesicles (EVs), play
important roles in a number of aspects of cancer progression. These include the ability of exosomes to
confer tumor cells with the capability to show resistance to chemotherapeutic reagents as well as to immune
therapy, together with their roles in promoting metastatic spread. We recently discovered that the down-
regulation of SIRT1 by aggressive breast cancer cells has an important influence on the numbers of
exosomes that they generate, the nature of the exosome cargo, as well as the composition of their total
secretome. This is due to the NAD+-dependent deacetylase/deacylase Sirtuin (SIRT1) playing a key role in
maintaining normal lysosomal function through a novel mechanism that ensures the proper expression of a
major subunit of the vacuolar ATPae (v-ATPase). We also have recently found that the formation and
shedding of exosomes appear to be dependent on the elevations in glutamine metabolism characteristic of
breast cancer cells (i.e. their ‘glutamine addiction’). These findings now raise important questions regarding
how the dependence of aggressive breast cancer cells on glutamine metabolism influences and/or works
together with the down-regulation of SIRT1 expression/activation to regulate lysosomal function and
exosome biogenesis, thus producing a secretome that stimulates cancer cell invasiveness and helps drive
the metastatic process. The different laboratories participating in this proposal will take advantage of their
multi-disciplinary expertise in biochemical and chemical biology approaches in probing cancer cell
metabolism and exosome biogenesis, high-resolution imaging, 3D spheroid culture and tumor organoids,
and the use of mouse models, in probing three key aspects of the mechanisms driving breast cancer
metastasis. These are: 1) Examining the relationship between SIRT1 down-regulation, elevated glutamine
metabolism and the generation exosomes with unique cargo by aggressive breast cancer cells. 2)
Understanding how SIRT1 down-regulation impacts vacuolar ATPase expression to generate a secretome
capable of promoting cancer cell invasiveness. 3) Determining how SIRT1 expression/activity affects
exosome production, cell invasiveness and metastatic spread in breast cancer models. The expectation is
that these studies will lead to the identification of exciting new treatment strategies for the devastating effects
of aggressive breats cancers, and ultimately, for other metastatic diseases.

Grant Number: 5R01CA259195-05
NIH Institute/Center: NIH
Principal Investigator: MARC ANTONYAK