TPH1 and cancer: However, when TPH/C6 was added to A549/ADR cells that contained saturated HA, the cellular uptake efficiency of the targeted TPH/C6 decreased substantially due to the competitive binding of free HA and CD44 on the cancer cells, suggesting that the endocytosis of TPH/C6 nanomicelles by A549/ADR cells was greatly facilitated by CD44-mediated internalization.