All cells have a suicide mechanism called "apoptosis." This mechanism is activated whenever a cell undergoes serious damage. One of the problems in cancer is that the cancer cells often lose or disable that mechanism. With many kinds of cancer treatments designed to activate apoptosis, loss of this causes cancers to fail to respond to therapy. A treatment that would restore apoptosis in the method described in the full article at the link might not directly kill cancers, but it would restore susceptibility to therapy.
While it is true that cancers have considerable genetic heterogeneity, there are certain features that are common to many cancers. Being able to target one of these features would be a great step forward.
Quite true — but cancer has a nasty way of evading and surviving vulnerabilities even where animal studies have shown great success. So far, the new drug has not even been tried in humans, let alone shown to be safe and effective.