In support of this, Tawfeeq et al. observed correlations between stress-responsive enhancement of the expression of HSP70 (along with HSP90) and expression of cancer stemness markers CD44, ALDH1A1, and ABCG2 in esophageal adenocarcinoma cells (SKGT-4 line) undergoing starvation with the depletion of glucose and serum factors [78]. This evidence concerns the gene ABCG2 and cancer.