ID1 and neoplasm: Id1 silencing (alone or in combination with anti-PD-1 therapy) significantly reduced tumor growth (C57-LLC_shID1/PBS: 947.6 [540.3-1334]; C57-LLC_shID1/PD-1: 1255 [1130-1359]; IDKO-LLC_shID1/PBS: 312.9 [30.07-596.7]; IDKO-LLC_shID1/PD-1: 47.09 [10.96-100.3], and p-values for the groups were as follows: C57-PBS/IDKO-PBS p = 0.0352; C57-PBS/IDKO-PD-1 p = 0.0066; C57-PD-1/IDKO-PBS p = 0.0027; C57-PD-1/IDKO-PD-1 p = 0.0007) (Supplementary Figures S1C, D).