CCR7 and neoplasm: CCL21a is a chemokine that promotes the growth and metastasis of many tumor types, including melanomas, breast, thyroid, colon, head, and neck cancers, via pairing with CCR7 expressed on tumor cells.[13] In addition, forced expression of CCL21a is also found to elicit potent antitumor immunity in clinical trials.[14] It is thus reasonable to assume that a higher concentration of CCL21a released from the hydrogel could divert TdLN metastatic cancer to the hydrogel.