Page 34 - SDIR5 Abstract book 21 12 2021.

IMAGING IN CANCER

Session: Imaging in cancer
LECTURES

Real-time microscopy of invasive cancer cells in the tumor microenvironment context

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Bojana Gligorijević
1 Temple University, USA

Tumor cell structures that have long been hypothesized as necessary for metastasis are invadopodia,
invasive protrusions rich in structural and adhesion proteins, as well as metalloproteases. Using our unique
intravital imaging approaches (Perrin et al, 2019 Cancer Rep; Bayarmagnai et al, 2018 Meth Mol Biol.), we
previously demonstrated that invadopodia in vivo are necessary for intravasation and consequent lung
metastasis (Gligorijevic et al, Plos Bio 2014).
To assemble invadopodia, cells are required to enter, but not complete EMT transition. Cells which do not
assemble invadopodia cannot metastasize individually, but only as a part of a cluster with invadopodia-
assembling cells (Perrin et al, 2021 BioRxiv). Such clusters require cell-cell adhesions.
In primary breast carcinoma, we found that cells which assemble invadopodia migrate at slow speeds, in
perivascular niches where the ECM is cross-linked. Outside of these niches, no invadopodia were observed
and cells migrated at high speeds, via contact guidance along collagen fibers. Invadopodia emergence is
independent of EMT status and can occur in individually invading cells, or leaders of collectively invading
cells. The invadopodia-driven motility can be switched to contact guidance by reducing the ECM cross-
linking or by knocking down Tks5, which in turn reduces intravasation and metastasis.
We next deduced that invadopodia-driven motility consists of two oscillating states: i. Invadopodia state,
in which a cell is relatively sessile while it assembles invadopodia and degrades ECM; ii. Locomotion state.
State balance is regulated by integrin β1 activation levels (Esmaeili et al 2018 Biophys J).
Importantly, the Invadopodia state only occurs in early G1, whereas the Locomotion state can be seen
throughout the entire cell cycle, suggesting that the cell cycle controls invadopodia assembly. Using FUCCI
markers (Esmaeili et al 2018 APL Bioeng), we next show that Invadopodia state occurs during the G1 phase
of the cell cycle (Bayarmagnai et al, 2019 J Cell Sci). A close look at the regulators of G1 revealed that the
cell cycle regulator p27kip1 localizes to the sites of invadopodia assembly and overexpression of p27kip1
causes faster turnover of invadopodia and increased ECM degradation, while reducing cell migration
efficiency.
Taken together, these findings suggest that invadopodia assembly, which occurs in the perivascular niche,
is necessary for lung metastasis and function is controlled by the cell cycle.

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