can cancer be cured?

yes. some. A good example of inhibition of cancer, approaching cure:

In laboratory studies, researchers at the Marie Curie Research Institute in
Britain reactivated a natural self-defence mechanism that is shut off in skin
cancer cells and forced them into a state of senescence, or coma, stopping them
from dividing and growing. "It offers a real hope we will be able to tackle cancer
by putting cells into a permanent coma," Thomas Hughes-Hallett, chief executive of
the Marie Curie Cancer Care charity, told a news conference.
Dr Colin Goding and his team were studying a gene called Tbx2 which is overactive
in melanoma, the most serious type of skin cancer, when they discovered it was
linked to a mechanism that repressed senescence. "What really surprised us was
that when we inhibited Tbx2 in melanoma cells, they senesced and stopped dividing.
This means we have potentially a new way of stopping cancer cells dividing," said
Goding.
Cancer develops when certain genes are mutated and cells divide uncontrollably.
Goding compared it to an accelerator in a car being jammed on. Normal, healthy
cells know something is wrong – the accelerator is jammed – and put on a brake or
senescence. But in cancerous cells the brake is missing or switched off.
The scientists inhibited the action of Tbx2 in melanoma cells in culture with a
technical trick. They discovered that the senescence mechanism was still there but
had been switched off by the Tbx2 gene. "What we have done is switched it back
on,"