Until a decade ago, Polybia paulista wasn’t well known to anyone other than entomologists and the hapless people it stung in its native Brazil. But then, a number of research groups discovered a series of remarkable qualities all concentrated in the aggressive wasp’s venom.
One compound in particular has stood out for its antimicrobial and anti-cancer properties. Polybia-MP1, a peptide, or a string of amino acids, is different from most antibacterial peptides in that it’s only toxic to bacteria and not red blood cells. MP1 punches through bacteria’s cell membranes, causing them to die a leaky death. Scientists had also discovered that MP1 was also good at inhibiting spreading bladder and prostate cancer cells and could kill leukemia cells, but they didn’t know why it was so toxic only to tumor cells.
Well, now they think they have an idea. How MP1 kills cancer cells turns out to be very similar to how it kills bacteria cells—by causing them to leak to death. MP1 targets two lipids— phosphatidylserine, or PS, and phosphatidylethanolamine, or PE—that cancer cells have adorned on the outside of their membranes. Here’s Kiona Smith-Strickland, writing for Discover:
MP1’s destruction of a cancer cell, researchers say, has two stages. First, MP1 bonds to the outer surface of the cell, and then it opens holes or pores in the membrane big enough to let the cell’s contents leak out. PS is crucial for the first part: seven times more MP1 molecules bound to membranes with PS in their outer layer. And PE is crucial for the second: Once the MP1 molecules worked their way into the membrane, they opened pores twenty to thirty times larger than in membranes without PE.
Even better, healthy cells have neither PS nor PE on the outside of their membranes. Rather, they keep them on the inside, a key difference from cancer cells that would shield them from the damaging effects of MP1. In other words, MP1 could make an ideal chemotherapy.
Photo credit: Prof Mario Palma/Sao Paulo State University