CKLF-like MARVEL transmembrane domain-containing family (CMTM) is a family of proteins linking classical chemokines and the transmembrane-4 superfamily (TM4SF).In humans,they are encoded by nine genes,including chemokine-like factor (CKLF) and CMTM1 to CMTM8 [1].Of these,CKLF1,CMTM1,and CMTM2 are related to chemokines,whereas CMTM8 is related to TM4SF11.The characteristics of other CMTM members are intermediate between those of CMTM1 and CMTM8.MARVEL domain-containing proteins usually have no signal peptide,but several reports have shown that MARVEL proteins,like MAL and CMTM5,are secreted via a vesicle-mediated secretory pathway [2,3].CMTM3 is the most closely related to CMTM5-v1 in the CMTM family,with 42％ amino acid identity.However,by far,CMTM3 is known as a membraneassociated tumor suppressor protein [4].Thus,it is necessary to know if CMTM3 can be secreted in vesicles.