VGF and neuroendocrine carcinoma: Matsumoto, T., et al. believed that VGF is only expressed in neuroendocrine carcinoma-derived cells and can be used as a new serological diagnostic marker for pulmonary neuroendocrine tumors [65]. PGC-1α is a crucial transcription regulator of genes that control energy metabolism and mitochondrial biogenesis through its partner transcription factors: nuclear respiratory factors and PPARs [66].