In order to evaluate whether the observed increase in apoptosis of NPC cells by chloroquine when combined with radiation was due to the blockade of autophagy, expression of autophagy-related genes ATG3, ATG5, ATG6 and ATG7 was silenced by specific siRNAs and apoptosis was determined by analysis of subG1-DNA content and measurement of active caspase-3. Here, ATG5 is linked to nasopharyngeal carcinoma.