We have also used a proteomic approach to gain insights into the mechanism of protection at the protein level by n-3FA in the absence and in the presence of Tamoxifen [ 26 ]. Using the isobaric tags for relative and absolute quantitation (iTRAQ) followed by confirmation by western blots, we found that increasing ratios of n-3FA : n-6FA in the diet induced dose-dependent changes in the plasma level of several proteins in a manner consistent with chemoprevention. Those included an increase in gelsolin and vitamin D binding protein, both shown to have tumor protective properties [ 27 , 28 ]. A high ratio of n-3FA : n-6FA also increased the expression of 14-3-3 sigma, a well-known tumor suppressor gene [ 29 ]. In contrast, alpha-1 β -glycoprotein, shown to be increased in a variety of cancers [ 30 – 32 ] was reduced by a high n-3FA diet. We also observed that the combined administration of Tamoxifen with a high ratio of n-3FA : n-6FA altered additional proteins also in a manner consistent with chemoprevention (Figure 5 ) [ 26 ]. These changes included a reduction in apolipoprotein E, haptoglobin, and inter-alpha inhibitor H4 heavy chain all shown to have tumor promoting properties [ 33 – 35 ]. Measurement of these differentially regulated proteins could be useful for monitoring the efficacy of n-3FA and Tamoxifen as chemopreventive agents in clinical trials.