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:To further investigate whether signaling upstream of JNK1/2 is also influenced, we examined the activation of MEK, MKK3/6, MKK4 and MKK7, which activate downstream JNK1/2(31-33).
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