MACAU -- Life has never been simple for Antonio DeMarco, who grew up so poor in Mexico that he had to search through trash cans and dumpsters in hope of finding something to eat.

Despite the many hardships he endured in his early life, DeMarco found success as a professional boxer and once held the WBC lighweight title before losing it to Adrien Broner.

He's reeled off three consecutive wins since then and added Hall of Famer Freddie Roach as his trainer as he prepares Saturday (Sunday in China) to face Jessie Vargas for the WBA junior welterweight title on the HBO Pay-Per-View card headlined by a welterweight title clash between Manny Pacquiao and Chris Algieri.

But DeMarco (31-3-1, 23 KOs) will fight with a heavy heart on Saturday. While he was in training camp in the Philippines, he learned that his 13-year-old sister, Mariana Soto, is suffering from bone cancer. A large tumor was growing on her shoulder  that DeMarco said was life-threatening. He said doctors had considered amputating her arm, but have put that off for now.

He dedicated the fight to her and said her relentless optimism in spite of the bad news has inspired him.

"She is braver than I am," DeMarco said. "A lot braver. She is fighting for her life and all I'm doing is fighting on top of a ring. I just spoke to her and it motivates me so much hearing how hard she is fighting. She is the one who has it difficult and she's so brave."

Dealing with adversity has been a theme of DeMarco's life. He has been saddened by his sister's illness, and is thinking of her daily, but said he hasn't allowed himself to be brought down.

He's a relentlessly positive and optimistic guy who has accepted his plight as well as anyone could imagine.

"It makes me strong, what God and life have brought to me," DeMarco said. "I wouldn't change it for anything. It's made me the person I am now. I love my family and I love the sport of boxing and I love giving the fans a good show. But what I want to do most is give my sister a very special win."