BRCA2 and lung cancer: Low expression of BRCA2 has been observed in LUAD.[130] Hsa_circ_100395 functions as a sponge for miR-1228 targeting TCF21 in lung cancer.[131] Decrease of TCF21 mRNA level is predictive of poor prognosis in patients with LUAD.[132] TCF21 overexpression in H1299 cell has also been shown to suppress tumor growth in a mouse model.[133] The mechanism of hsa_circ_000122 is unknown.[118]