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:loss was tested in the context of overexpression of the oncogene NRAS and a short hairpin against p53, because ATRX mutation by itself is not associated with cancer development in humans (12), and glial tumors with ATRX mutations almost always include TP53 mutations (1).
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