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Scientists discover gene that stops spread of lung cancer

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A team of researchers may have found a promising new route to fighting one of the world's deadliest cancers. They have discovered a gene that plays a role in metastasis or cancer spread of a common lung cancer. The gene helps cancer cells pull up their anchors in the primary tumor and move easily to new sites where they form new tumors.

The team, from the Salk Institute in La Jolla, CA, reports its findings in the journal Molecular Cell.

Lung cancer is the leading cause of cancer-related deaths among Americans. According to the National Cancer Institute, nearly 160,000 people will die of lung cancer in the US in 2014, and the nation spends more than $12 billion on treatments for the disease.

Yet despite this massive amount of spending, lung cancer has an appalling survival rate. Within 5 years of diagnosis, 4 out of every 5 patients die - usually because the cancer spreads quickly to the rest of the body.

Metastasis relies on cells losing adhesion by 'lifting their anchors'

Researchers have so far established that for cancer to become mobile, cells in the primary tumor manage to overcome the normal cell's ability to keep itself rooted to where it belongs. Normal cells do not travel. Previous studies have shown that, in around a fifth of lung cancer cases, the patient is missing an anti-cancer gene known as LKB1.

Cancer cells become mobile because they have the ability to manipulate focal adhesion complexes - molecular protrusions that behave like anchors. In normal cells, the focal adhesion complexes keep them anchored in their proper locations in the tissue where they belong.

But cancer cells have the ability to "lift" their cellular anchors, leaving them free to travel via the bloodstream to other organs in the body and establish new tumors.

Previous studies have shown that various cancers have the ability to manipulate these anchors. They have also shown that in around a fifth of lung cancer cases, the patient is missing an anti-cancer gene known as LKB1 - that is also called STK11.

When the LKB1 gene is missing, the cancer is usually aggressive and spreads quickly to other organs. But, before this new study, nobody had linked LKB1 to focal adhesions.

Study is first to find link between anti-cancer gene LKB1 and adhesion of cells

The link was established with the help of another gene called DIXDC1. The team discovered that LKB1 communicates with DIXDC1, instructing it to change the size and number of the focal adhesions or anchors.

They found that when DIXDC1 is active, around half a dozen focal adhesions grow large and sticky and anchor their cells to the spot. When DIXDC1 is inactive or blocked, the large focal adhesions shrink and become hundreds of tiny "hands" that pull the cell forward in response to other signals. It is in this latter state that the cell is then free to travel to other sites.

First author and graduate student Jonathan Goodwin, says the "communication between LKB1 and DIXDC1

is responsible for a "stay-put" signal in cells. DIXDC1, which no one knew much about, turns out to be inhibited in cancer and metastasis."

He and his colleagues found two ways to turn off the stay put signal - perhaps the cancer cell uses one of them. One way was to block DIXDC1 directly, and the other was to delete LKB1, which then fails to send the instruction to DIXDC1 to move to the focal adhesions and anchor the cell.

Reactivating DIXDC1 in cancer cells slowed ability to travel

After showing these two methods the team then wondered if reactivating DIXDC1 could stop metastasis. They found it could. They took cancer cells that were spreading - so-called metastatic cells - found they had low levels of DIXDC1, and then overexpressed the gene.

The result was that switching DIXDC1 back on in metastatic cells did slow their ability to travel. They showed this in cultured cells and also in animal models.

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