NKX6-3 and gastric cancer: Additionally, AGS, MKN1, MKN28 and MKN45 gastric cancer cells also showed no expression of the NKX6.3 protein, whereas its marked expression was detected in AGS cells transiently transfected with NKX6.3 (Figure 1B), confirming tissue data and suggesting a role for NKX6.3 as a tumor suppressor.