LOS ANGELES - David Brenner, 78, the gangly, toothy 1970s Tonight Show favorite whose brand of observational comedy became a staple for other stand-up comedians, including Jerry Seinfeld and Paul Reiser, died Saturday, March 15, of cancer.

Mr. Brenner, a Philadelphia native, had been fighting the disease. He died at home in New York City with his family at his side, according to Jeff Abraham, his friend and publicist.

"David Brenner was a huge star when I met him and he took me under his wing. To me, historically, he was the godfather of hip, observational comedy," comedian Richard Lewis said in a statement. "He mentored me from Day One. . . . His passing leaves a hole in my life that can never be replaced."

Mr. Brenner's stand-up routines became a favorite of Tonight Show host Johnny Carson starting in the 1970s.

His 150-plus Tonight Show appearances turned the former documentary filmmaker into a hot comedian. Mr. Brenner was a regular on other TV talk shows and game shows and starred in four HBO comedy specials. He also briefly hosted his own syndicated talk show in 1987.

He moved with the times, trading routines about the humor of everyday life for jokes about social and political issues. He appeared on MSNBC and Fox News Channel cable programs as well as talk shows.

"David was one of the most respected and liked comedians by his peers. He was always there helping a bright young comedian, whether it be Richard Lewis, Freddie Prinze or Jimmie Walker, and he was still doing it until the very end," Abraham said.

A bio posted on Mr. Brenner's website recalls his Philadelphia childhood. It reads, "Brenner had grown up in poor sections of South and West Philadelphia where he was a gang leader who used humor as a negotiating tool."

As a major in mass communication at Temple University, Mr. Brenner worked for the campus radio station, first as background voice and then as a "gravel pit walker" - stomping on gravel, wood, and other items to replicate sounds for news segments.

For a time after graduation, he wrote, produced, and directed documentaries on news and social issues for KYW-TV.

Upon his induction into the Broadcast Pioneers of Philadelphia hall of fame in 2003, Mr. Brenner remembered his time as a local documentarian.

"I made the decision that nothing I had done on TV changed one damn thing - that Man has all the answers and solutions to the inequities, but just doesn't want to implement them, probably a combination of Man's innate evil and all the money that can be made from Man's suffering," he wrote on the group's website.

"So I quit trying to solve the problems and decided to make people laugh about them. Every so often, I see a new version of the same documentary that I did over thirty years ago. I should laugh, but I don't."

 Mr. Brenner was a "brilliant comic, but also an intellectual," Gerry Wilkinson, chairman of the board of the Broadcast Pioneers of Philadelphia, said Saturday.

Kal Rudman, publisher of the music and broadcasting tip sheet the Friday Morning Quarterback, described Mr. Brenner as one of the early comedians to tackle social issues. And despite leaving Philadelphia long ago, Brenner never forgot his native city, Rudman said.

"He was such a wonderful guy," Rudman said, "and from a personality and emotionality point of view, he loved Philadelphia with a passion," Rudman said.

 Mr. Brenner wrote five books, including the post-9/11 I Think There's a Terrorist in My Soup, published in 2003. His last HBO special, David Brenner: Back with a Vengeance, debuted live in 2000.

Mr. Brenner worked steadily through 2013 doing stand-up. A four-day gig in December included a New Year's Eve show at the Valley Forge Casino Resort, in which he showcased young comedians.