Apparently plants do develop tumors, but they don't metastasize because of cell walls that stop them from spreading. Also, like this article says ( http://www.popsci.com/article/science/ask-anything-do-plants... ), plants don't have vital irreplaceable organs, so tumors are less dangerous for them.

Just to nitpick, we're not only interested in curing cancer in humans. From elsewhere in this thread, a transmissible cancer that threatens an entire species, for which attempts have been made to find a cure or vaccine:

https://en.wikipedia.org/wiki/Devil_facial_tumor_disease

Humans evolution can be characterised into major stages from ape to homosapien.

No it can't. There were only many small adaptions, not stages. Stages also suggests that there is a next stage to evolve to which is not correct.

You are conflating 'evolution is directionless' with 'no stages'. Stages can only be seen when looking back at the evolutionary history.

For example:

Study reveals human body has gone through four stages of evolution (http://www.eurekalert.org/pub_releases/2015-08/bu-srh083115....)

http://www.pnas.org/content/112/37/11524.abstract

Stages are a human abstraction that help us understand and make sense.

You can say that for just about everything