The finger-like cells of the filamentous foot help control breast tumors

Researchers at the University of Turku and the University of Åbo Akademi have found that the extension of finger-like cells known as filamentous feet helps create a barrier
around breast tumors.

In the early stages of breast cancer, malignant cells are surrounded by a tissue barrier called the basement membrane, which prevents them from spreading to other parts
of the body.
This early-stage disease is usually not life-threatening because surgery can remove the tumor
.
However, if breast cancer spreads and metastases, it can be fatal
.

To escape and spread, tumor cells first need to break through their nearest barrier, the basement membrane
.
Cellular structures called filatopodia help protect the basement membrane surrounding the tumor and prevent the tumor from escaping
.

"These results are very surprising because we previously thought that the sticky fingers of these cancer cells were only used to invade nearby tissue
.
" Now we find that these structures can also help control tumors," says
Professor Johanna Ivaska, head of the InFLAMES group at the University of Turku.

These sticky hands are produced
by a protein called myosin-10.
The team, led by Dr.
Emilia Peuhu, a lecturer at the University of Turku's Institute of Biomedical Research, and Dr.
Guillaume Jacquemet, leader of the Inflammation Group and associate professor of cell biology, found that cancer cells lacking myosin-10 are unable to build and maintain the basement membrane
around them.
This makes it easier for cancer cells to escape
.

"After myosin-10 was removed, the tumor was significantly more aggressive
.
Their basement membrane has almost completely disappeared and they spread more freely to surrounding tissues," says
Dr Peuhu.

For years, Ivaska and Jacquemet's team has worked to understand how cancer cells use filamentous feet to move and invade surrounding tissues
.
Their previous findings highlighted that once cancer cells escape the primary tumor, filopodia can be used by cancer cells to spread
.
Now the team has found that filamentous feet play the opposite role
in the early stages of the disease.

Dr Jacquemet said: "We have been researching and developing anti-filamentous pseudopodia strategies to treat cancer, but our new results clearly highlight that targeting filopodia or myosin-10 too early can actually make the situation worse
.
"

The research team and their collaborators are now evaluating how filopodia regulates basement membrane assembly
.

The findings were published in
the journal Developmental Cell.

MYO10-filopodia support basement membranes at pre-invasive tumor boundaries