Sian's London Marathon

£25 could either buy 500 plastic test tubes, 5 boxes of gloves, 5 beakers, or a Bunsen burner, which are the understated tools of many experiments.

£50 can pay for chemicals called restriction enzymes, which cut long strands of DNA, allowing scientists to find out more about the genes that cause cancer.

Early diagnosis is essential to getting the right treatment to people with cancer. £100 could pay for a cancer biopsy, where a tiny amount of a lump is removed and sent to be studied in a lab.

£150 could fund a team of researchers in Manchester for half a day. They're trying to diagnose and monitor lung cancer in a less invasive way.

£200 can buy DNA nucleotides, something scientists use to make copies of genes, giving us clues about how things go wrong in cancer.

£300 could buy a device used to spin blood samples so different types of cells separate. Our scientists can then study the different types of cancerous cells to find out more about them.

£500 could run our online moderated forum, Cancer Chat, for a day. It's a safe space open to everyone to discuss any aspect of the disease with others in the cancer community.

To help test potentially life-saving treatments and find the most promising new cancer drugs, £1,000 could buy imaging software that our scientists use to film cells in real time.

The PETReA trial aims to help doctors decide how best to treat lymphoma, a cancer of the white blood cells. £2,500 could fund this trial for five days.