Milo, a Vancouver sea otter who achieved international fame through YouTube, has died of cancer.

A video of the animal holding hands with a fellow otter at the Vancouver Aquarium gained more than 16 million views after it was posted to the popular video-sharing website four years ago.

Staff say the 12-year-old male otter was diagnosed with lymphoma last August and became the first sea otter to receive chemotherapy in the world. He appeared to respond well to treatment for about six months, but succumbed to his illness on Wednesday.

"Our team—especially those who worked closely with Milo during the past months to provide specialized care while he was receiving treatment—are saddened by his death but take solace in his peaceful departure," Vancouver Aquarium general manager Clint Wright said in a release.

Staff say the medical treatment given to Milo, who was born in Portugal's Lisbon Aquarium, will improve veterinarians' understanding of sea otter diseases and responses to treatment.

Nyac, the 20-year-old female sea otter seen in the YouTube video with Milo, died of chronic lymphatic leukemia in 2008.

The Vancouver Aquarium's oldest resident came to the facility in 1989, along with eight other otter survivors of the deadly Exxon Valdez oil spill.