A study by researchers lead by Dr.Rajesh Agarwal,  shows that in both cell lines and mouse models, grape seed extract (GSE) kills head and neck squamous cell carcinoma cells, while leaving healthy cells unharmed. "It's
 a rather dramatic effect," says Rajesh Agarwal, PhD, investigator at 
the University of Colorado Cancer Center and professor at the Skaggs 
School of Pharmaceutical Sciences.
Grape seed extract creates these conditions that 
are unfavorable to growth. Specifically, the paper shows that grape seed
 extract both damages cancer cells' DNA
 (via increased reactive oxygen species) and stops the pathways that 
allow repair (as seen by decreased levels of the DNA repair molecules Brca1 and Rad51 and DNA repair foci).
"Yet we saw absolutely no toxicity to the mice, themselves," Agarwal says.
Interestingly,  the grape seed extract killed the cancer cells but not the healthy cells. As per the lead reseacher,  the  cancer
 cells have a lot of defective pathways and they are very vulnerable  and one can  target those pathways. The same is not true of healthy cells," 
adds Agarwal.
The Agarwal Lab hopes to move in the direction of 
clinical trials of grape seed extract, potentially as an addition to 
second-line therapies that target head and neck squamous cell carcinoma that has failed a first treatment.
Ref :  http://carcin.oxfordjournals.org/content/23/11/1869.abstract?sid=90421d40-8cea-478e-8d70-f5a17c4158b7