The discovery could lead to better treatments for cancerous tumors.
Salmonella is best known as the pesky bacteria found in contaminated meat or eggs that leads to food poisoning, but scientists at the University of Massachusetts Medical School have discovered a more beneficial use of the bacteria — the Salmonella protein SipA reduces a drug resistant molecule found in a number of different types of cancer cells.
"It is fascinating to think that this discovery has incredible clinical potential for treating certain drug resistant cancers,” lead author Beth A. McCormick, professor of microbiology & physiological systems at UMass Medical School, said in a press statement. “On the strength of these findings, we're already moving into pre-clinical development.”
In the new study, which appears in the journal Nature Communications, researchers dramatically boosted tumor sensitivity to chemotherapeutic drugs by delivering the Salmonella protein attached to tiny gold nanoparticles. Colon and breast cancer tumors in mice were also found to shrink as a result of the SipA.
"Outside of the bacteria, the SipA protein was too unstable to simply inject into a potential patient," Gang Han, associate professor of biochemistry and molecular pharmacology at UMMS, said in the release. "Rather than using the whole bacteria, we developed a nanoparticle scaffold to mimic the bacteria and stabilize and deliver the protein. We refer to this particle as a 'nanobug.'"
The scientists chose gold as the nanoparticle scaffold due to its immobile nature, and developed the “nanobug” to be small enough to infiltrate a cancerous tumor but large enough to avoid being absorbed by most biological tissues.
Along with the widely used chemotherapy drug Doxorubicin, the researchers injected the SipA-nanobug into mice with colon cancer and a humanized mouse model with breast cancer.
"The results were astonishing," said Mercado-Lubo. "After 30 days the tumors were almost undetectable. It was remarkable. In some cases the tumors became little more than thin slices of tissue."
Plus, there was no buildup of the gold nanoparticle in the lung, cardiac, or brain tissues.
Going forward, the researchers plan to determine the safety, toxicity and dosage levels in order to move the nanobug into trials with humans.
"The bacterial nanoparticle mimic we've developed it has the potential to stabilize therapeutic proteins and to be used in conjunction with a wide variety of clinical used chemotherapeutic drugs to overcome multidrug resistance in a variety of tumors," Han concluded.