We’ve all heard the cliched legends of an actor’s struggles before a career triumph: living hand to mouth, waiting tables, temping, couch surfing and generally scraping by before landing that major role.

The star of “A Dog’s Way Home,” which is currently in theaters, has a hard-luck tale that could top them all. Before her big break, she was surviving in a landfill, tearing through garbage for her next meal.

Meet Shelby, the tan-and-black mutt who plays Bella, occupying the screen, often solo, for much of the film’s 97 minutes – and whose trash-to-riches saga could itself be a gripping cinematic tale.

Shelby’s huge break came in April 2017, when animal-control officer Megan Buhler was on a stroll in Cheatham County, Tennessee, a rural area about 25 miles from Nashville. Out on a normal call, Buhler spotted and approached what she recalled was a very skittish dog hiding in the dump.

“So I knelt down and just said, ‘Oh, come here, baby,’ ” said Buhler, 29. “There were lots of cars driving by – I mean, it was heavy traffic. She was so scared, and she finally came right up to me, and I was able to put her in my truck.”

The two headed to the county animal shelter, where the staff started calling the new resident Baby Girl.

Buhler and TJ Jordi, then the shelter’s animal-control director in charge, had no idea that 2,000 miles away, Hollywood was looking for a pup to play Bella in a film written by Cathryn Michon and W. Bruce Cameron and based on Cameron’s novel.

A central plotline involves breed-specific legislation or local laws that prohibit certain dog breeds from living in specific municipalities or counties. In this case, the focus was Denver’s ban on “pit bull breeds.”

Cameron is an incredible author who specializes in dog books, perhaps most notably “A Dog’s Purpose,” which was on the New York Times bestseller list for nearly five months and was made into a 2017 movie starring Dennis Quaid. (A sequel to that film, “A Dog’s Journey,” opens May 17.)

Cameron and Michon, who are currently married, are huge dog lovers and say part of their love is expressed by advocating for homeless dogs whenever possible.

“We started off in the very beginning saying that the dog that is the star of the movie will have to be a rescue, because we were trying to prove something,” Cameron said. “We think we’re making a difference in the animals’ lives when they are adopted, and we’re trying to reveal to the world that rescue dogs are wonderful animals.”

The filmmakers brought on trainer Debbie Pearl, whose company Paws for Effect functions as an animal talent agency of sorts, one known for finding adoptable dogs and training them for on-screen roles.

Pearl then gave the find-a-Bella job to Teresa Ann Miller, a freelance trainer whose resume includes “White God,” an acclaimed 2014 Hungarian film that features more than 200 dogs. Miller’s mission was to search shelters nationwide for a dog that could star as Bella – and then give her the acting chops to do it.

“We initially started looking for a kind of Rottweiler/shepherd/pit bull mix,” Miller said. “That’s kind of what (Cameron’s) book cover looked like to me.”

In the meantime, back in Tennessee, Baby Girl was already getting special treatment. The shelter’s staff believes that taking stellar photographs of its animals immensely boosts their adoption chances. Jordi, the former animal-control director, recalled being so encouraged by the outcomes of the earliest photos that he “eventually built things up to the point we actually had a full studio setup.”

One day, Miller saw Baby Girl’s adoption photo, which Jordi had taken.

“Honestly, it was a really good picture, and she was flat-out smiling,” Miller said. “I mean, it was beautiful.”

Still, Miller was apprehensive. Two promising pup candidates already had not panned out, and a third possible Bella had been adopted out of a Los Angeles shelter the night before Miller was scheduled to meet and videotape the dog.

But the Miller-Baby Girl summit went off without a hitch, spanning two hours, with the trainer evaluating her new friend on personality, temperament and the ability to respond to simple commands. Miller was sold.

Within a couple of weeks, Cameron and Michon traveled to Tennessee, met Baby Girl and fell under the same spell. In an email, Michon said that she was shocked by “the extraordinary sweetness of her soul.” Baby Girl, she added, “was loving, smart, oh-so-eager to please, and we knew instantly we had found our Bella.”

Quickly, Miller adopted Baby Girl from the shelter on behalf of Pearl and Paws for Effect, gave her the new name Shelby (“a really cute Southern name”) and took her to California for training.

Miller stated that her approach shows off the style of her late father, a well-known Hollywood animal trainer, eschewing rapid commands in favor of talking in sentences to elicit more relaxed state.

“Instead of saying, ‘Come, sit, stay,’ – you know, all these sharp commands where the dog’s looking at the trainer – we might say: ‘Can you come over here? Hey, what are you doing?’ ” Miller explained. “She’ll stop and she’ll look around a little bit more, and I’ll say, ‘Why don’t you go … go lie down, put your feet up.’ And she’ll start to do it, and I’ll say, ‘That’s good.’ … So it’s kind of a different type of training technique.”

Miller and Shelby were training for just over three months before filming began. Then they were side by side each day on the set. Most of the film’s reviews, thumbs up or down, have loved Shelby’s performance. Variety wrote that the film “is at its best when relying on Shelby and her trainers: It’s amazing how much of the humor, drama and emotion is carried on her canine shoulders.”

Shelby now resides with Pearl in Huntington Beach, California. And at age 2½, Shelby has turned out to be as gifted a therapy canine as a thespian, Pearl said.

“She just has this insight of what she needs to do when she needs to do it,” Pearl said. “And not all dogs have that, even dogs that I’ve used for therapy dogs for a long time.”

Shelby has come a long way from her humble beginnings. But Buhler, the animal-control officer, said she saw Shelby recently and needed only a split-second to compare the movie star with the dog she coaxed away from piles of trash.

“She’s exactly the same,” Buhler said.