FGF4 and neoplasm: To investigate whether FGF4/SHH could support tumor progression inhibited by knockdown of GREM1, we pre-treated CAF-derived exosomes (Exo-KD 1#) in combination with AAV carrying an F4/80 promoter of SHH (Exo-KD 1# + AAV-SHH) or FGF4 (Exo-KD 1# + AAV-FGF4) or control AAV-NC (Exo-KD 1# + AAV-NC), followed by LLC administration (Fig. 8A).