(Adds details on clinical trial alliances, background)

LONDON, Nov 4 (Reuters) - AstraZeneca moved to strengthen its core oncology business on Tuesday with three deals designed to expand the British drugmaker's reach in treating tumours.

The collaborations include an agreement to buy Definiens, a private company that has developed a way of unlocking information from cancer tissue samples, for an initial $150 million, and two alliances to test novel drug combinations.

Definiens, whose imaging and data analysis technology was developed by Gerd Binnig, the 1986 Nobel Laureate in physics, will be folded into AstraZeneca's biotech arm MedImmune.

Using so-called "biomarker" tests is an increasingly important part of cancer medicine, where therapies are more and more being targeted to match the genetic profile of different patients.

Separately, AstraZeneca has also struck collaborations with U.S. firms Pharmacyclics and Johnson & Johnson to combine its drugs with their medicine Imbruvica against cancer.

Exploring combination therapies is a central part of AstraZeneca's oncology strategy and an area where the group believes its long experience in cancer medicine may give it an edge over rivals.

The two new clinical trial partnerships also extend the focus of AstraZeneca's drug combination work in the fast-growing -- and highly promising -- field of immunotherapy, where AstraZeneca is vying with competitors like Bristol-Myers Squibb , Merck & Co and Roche.

While AstraZeneca already has a number of immunotherapy trials underway in solid tumours, including lung cancer, the latest collaborations extend that research into haematological, or blood, cancers.

(Reporting by Ben Hirschler and Paul Sandle; Editing by Neil Maidment and William Hardy)