Disclosed is a method comprising the following steps: (a) contacting a sample containing cancer cells from a subject with an inhibitor of Hsp90 selected from PU-H71 or a derivative thereof, which inhibitor of Hsp90 preferentially binds to tumour-enriched Hsp90 complexes in which the Hsp90 is bound to cancer-implicated pathway components present in the sample, as compared with its binding to housekeeping Hsp90 that is not present in such complexes； (b) detecting pathway components present in the tumour-enriched Hsp90 complexes to which the Hsp90 inhibitor selected from PU-H71 or a derivative thereof preferentially binds； (c) analysing the detected pathway components of step (b) so as to identify a pathway which includes at least the detected components； (d) selecting an inhibitor of the pathway as a cancer therapeutic agent (&rdquo；a selected inhibitor&rdquo；) for co-administration to the subject with an Hsp90 inhibitor； and ( e) wherein the selected inhibitor is to be administered in combination with the Hsp90 inhibitor.
