For the first time in his career, Jennings hit the canvas as Tupou caught him off-balance in the third round. But Jennings persevered and the fighter, who holds a day job as a mechanic and lives with his grandmother, improved to 16-0 with eight knockouts. His dream of a world championship remains a possibility.
On the undercard, North Philadelphia super middleweight Jesse Hart easily outpointed Steven Tyner in a four-round unanimous decision.
The bout was the first time in his career that Hart (5-0, 4 KOs) had fought past the third round. Tyner (3-9-2) has now lost four straight bouts.
Hart is trained by his father, legendary Philadelphia middleweight Eugene "Cyclone" Hart, who started his career with 19 straight knockout victories.
Hart said he was offered a bout on the undercard of Saturday's Manny Pacquiao vs. Juan Manuel Marquez pay-per-view, but his match would not be televised.
"I said, 'If I'm not going to be televised, then I want to fight in my hometown,' " said Hart, who has already fought twice in Las Vegas this year.
Saturday night's win may have marked the last of Hart's bouts against second-tier opponents, as Top Rank Promotions will begin to groom him for bigger fights in 2013.
He won 85 of his 96 amateur bouts and captured the 2011 National Golden Gloves and USA National Tournament titles.
"They said they have a lot of big plans for me," Hart said. "They said we're going to take off. I think Vegas will be the main stage for me."
Contact Matt Breen at firstname.lastname@example.org.