In particular, Balic et al. showed that chloroquine preferentially eliminates Pa-CSCs in primary PC cell cultures by promoting internalization of C-X-C chemokine receptor type 4 (CXCR4) in CSCs, thereby decreasing cell sensitivity to chemokine (C-X-C motif) ligand 12 (CXCL12). This evidence concerns the gene CXCR4 and pachyonychia congenita.