APOB and amyotrophic lateral sclerosis: Among the 53 candidate ALS biomarker proteins, 44 proteins are novel, and 9 proteins were identified previously as being differentially expressed in ALS, and these include neurofilament proteins (NEFL, NEFM, and NEFH), CHIT1, CHI3L1, CHI3L2, APOB, GPNMB, and UCHL1 [20,41,42].