CTSD and breast cancer: As to LC and normal group, the 20 top proteins with the highest BC were APP, ACTB, NCAM1, APOB, PRNP, CDH2, SPP1, CRP, FGA, PIGR, CTSD, HP, APLP1, ENO2, AGT, CNTN2, SOD1, TIMP1, ITIH3 and NRXN1 (Supplementary Fig. 6).