By Nigel Powlson

IT will take a strong constitution a box of four-ply Kleenex for most film-goers to get through My Sister's Keeper.

That's because this is a shameless weepie that will tug ceaselessly at your heart-strings.

It's based on the best-selling novel by Jodi Picoult and its central premise offers a moral dilemma that no parent would want to face. How much pain would you put your healthy child through in order to save your sick one?

For 15-year-old Kate (Sofia Vassilieva) life is a series of hospital beds and painful treatments. She's only managed to survive into her teens at all because her parents (Cameron Diaz and Jason Patric) had another daughter who was genetically chosen to be a donor for Kate.

But after years of bone marrow and stem cell donation, 11-year-old Anna (Abigail Breslin) draws the line at giving up a kidney when her sister suffers renal failure.

To stop her mum forcing the organ donation through, she goes to a hot-shot lawyer (Alec Baldwin) and sues her parents for "medical emancipation" .

Most of the acting is convincing; especially Vassilieva as the brave cancer patient and Diaz as her self-sacrificing mother. Only Breslin comes across as unnatural. But the constant round of cancer wards and emotional heartache set to heart-plucking score is painful even if well done.