New gene discovered that stops the spread of deadly cancer

In addition to different cancers being able to manipulate these anchors, it was also known that about a fifth of lung cancer cases are missing an anti-cancer gene called LKB1 (also known as STK11). Cancers missing LKB1 are often aggressive, rapidly spreading through the body. However, no one knew how LKB1 and focal adhesions were connected.

Now, the Salk team has found the connection and a new target for therapy: a little-known gene called DIXDC1. The researchers discovered that DIXDC1 receives instructions from LKB1 to go to focal adhesions and change their size and number.

When DIXDC1 is "turned on," half a dozen or so focal adhesions grow large and sticky, anchoring cells to their spot. When DIXDC1 is blocked or inactivated, focal adhesions become small and numerous, resulting in hundreds of small "hands" that pull the cell forward in response to extracellular cues. That increased tendency to be mobile aids in the escape from, for example, the lungs and allows tumor cells to survive travel through the bloodstream and dock at organs throughout the body.

"The communication between LKB1 and DIXDC1 is responsible for a 'stay-put' signal in cells," says first author and Ph.D. graduate student Jonathan Goodwin. "DIXDC1, which no one knew much about, turns out to be inhibited in cancer and metastasis."

Tumors, Shaw and collaborators found in the new research, have two ways to turn off this "stay-put" signal. One is by inhibiting DIXDC1 directly. The other way is by deleting LKB1, which then never sends the signal to DIXDC1 to move to the focal adhesions to anchor the cell. Given this, the scientists wondered if reactivating DIXDC1 could halt a cancer's metastasis. The team took metastatic cells, which had low levels of DIXDC1, and overexpressed the gene. The addition of DIXDC1 did indeed blunt the ability of these cells to be metastatic in vitro and in vivo.

"It was very, very surprising that this gene would be so powerful," says Goodwin. "At the start of this study, we had no idea DIXDC1 would be involved in metastasis. There are dozens of proteins that LKB1 affects; for a single one to control so much of this phenotype was not expected."

Right now, there is no specific treatment for cancers harboring LKB1 or DIXDC1 alterations, but those with a deletion of either gene would likely see results from cancer drugs that target the focal adhesions, says Shaw.

Salk scientists have discovered the gene responsible for the aggressive spread of a common lung cancer.

(Photo Credit: Salk Institute for Biological Studies)

"The good news is that this finding predicts that patients missing either gene should be sensitive to new therapies targeting focal adhesion enzymes, which are currently being tested in early-stage clinical trials," says Shaw, who is also a member of the Moores Cancer Center and an adjunct professor at the University of California, San Diego.

"By identifying this unexpected connection between DIXDC1 and LKB1 in certain tumors, we have expanded the potential patient population that may be good candidates for these therapies," adds Goodwin.

Focal adhesion complexes (bright green) are typically large and sticky, anchoring a cell into place (left). When the gene DIXDC1 is knocked out, focal adhesion complexes instead become small and numerous, readying cancer cells to move into the bloodstream and become metastatic (right).

(Photo Credit: Salk Institute for Biological Studies)

This image depicts Jonathan Goodwin and Reuben J. Shaw, Salk professor of molecular and cell biology

(Photo Credit: Salk Institute for Biological Studies)

Source: Salk Institute