Evaluate the collective function of references cited together in a given text segment.
Classify their combined role into one of the following categories: 'method', 'background', or 'result'.

Text:The emerging data from clinical trials with GDC-0449 show both the benefits and possible pitfalls of a pure SMO antagonist; a clear tumor response in Hh driven tumors such as basal cell carcinoma and medulloblastoma [34,55,56], and the occurrence of a drug induced resistance caused by mutations in the Smo locus [34,55].
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