We report the investigation of label-free protein detection directly from lysed cells using microcantilever sensors. The integration of an internally referenced microcantilever sensor combined with peptide aptamer technology enables scalable and label-free detection of proteins from a complex biological environment (e.g. cell lysate). The internally referenced microcantilever sensor was found to be effective in minimizing both the effects of thermal drift and non-specific binding interactions with the backside of the cantilever, thereby allowing protein detection in a complex biological background. Highly specific peptide aptamers are used to modify the cantilever surface to specifically detect less than 80 nM CDK2 protein from yeast cell lysate. This binding of CDK2 on the microcantilever generates a tensile surface stress of average magnitude equal to 70+/-22 mN/m. Similar experiments conducted with quartz crystal microbalance (QCM) technology are consistent with the response observed using microcantilever sensors.