NEDD9 and Chromium(VI) Carcinogenesis

Cr(VI) compounds are carcinogenic to humans. The underlying mechanism remains unknown. Neural Precursor Cell Expressed Developmentally Down-regulated Protein 9 (NEDD9), a multi-domain scaffolding protein, is crucial for tumorigenesis. High expression of NEDD9 is correlated with advanced clinical stage of non-small cell lung carcinomas (NSCLC). Autophagy is a key regulator that maintains p62 at desired levels. Upregulation of p62 is associated with various carcinogenic processes. Our preliminary studies show that in Cr(VI)-transformed cells, NEDD9 is upregulated, and autophagy is impaired, resulting in the upregulation of p62, Nrf2, and Bcl-2. Knockdown of NEDD9 decreases p62 and Nrf2 expression and reduces the malignancy of Cr(VI)-transformed cells. Knockdown of p62 or Nrf2 suppresses tumorigenicity of Cr(VI)-transformed cells. Overexpression of p62 in BEAS-2B cells causes malignant cell transformation and tumor growth. Among the six main domains/regions of p62, the TNF receptor-associated factor 6 (TRAF6)-binding domain (TB) binds to and phosphorylates TRAF6, leading to NF-κB activation, and the Keap-interacting region (KIR) binds to Keap1, causing constitutive Nrf2 activation. HIF-1α, a key regulator of angiogenesis, is upregulated in Cr(VI)- transformed cells and knockdown of NEDD9 reduces its expression. The central hypothesis is that in normal cells ROS generated by Cr(VI) overwhelms the protection of autophagy, causing NEDD9 upregulation, eventually malignant cell transformation, that in Cr(VI)-transformed cells NEDD9 upregulation impairs autophagy, causing upregulation of p62, which then activates NF-κB and Nrf2, and subsequently upregulation of its downstream anti-inflammatory and anti-apoptotic proteins, and that NEDD9 positively regulates HIF-1α, resulting in tumorigenesis of Cr(VI)-transformed cells. Aim 1 will test the hypothesis that chronic exposure of cells to Cr(VI) generates ROS and induces autophagy, that autophagy protects against Cr(VI)-induced malignant transformation by decreasing ROS level through facilitating mitochondrial turnover, and that ROS generated by Cr(VI) overwhelms the protection of autophagy, resulting in NEDD9 upregulation and eventually malignant cell transformation. We will investigate the protective role of autophagy against Cr(VI)-induced cell transformation via the decrease of ROS through facilitated mitochondrial turnover and the role of NEDD9 upregulation by Cr(VI)-induced ROS in malignant cell transformation. Aim 2 will test the hypothesis that in Cr(VI)-transformed cells upregulation of NEDD9 impairs autophagy, causing accumulation of p62, subsequently activation of NF-κB and Nrf2, and that NEDD9 upregulates HIF-1α, leading to increased cell survival, angiogenesis, and tumorigenesis. We will investigate that NEDD9 upregulates p62, then NF-κB activation and constitutive Nrf2 activation, and its downstream inflammatory and anti-apoptotic proteins, as well as HIF-1α in tumorigenesis of Cr(VI)-transformed cells. Aim 3 will investigate the role of NEDD9 in the mechanism of Cr(VI) carcinogenesis using NEDD9 wild-type and knockout animals exposed to Cr(VI). Project Number: 1R01ES037266-01 | Fiscal Year: 2025 | NIH Institute/Center: National Institute of Environmental Health Sciences (NIEHS) | Principal Investigator: Max Costa | Institution: NEW YORK UNIVERSITY SCHOOL OF MEDICINE, NEW YORK, NY | Award Amount: $2,518,755 | Activity Code: R01 | Study Section: Environmental Determinants of Disease Study Section [EDD] View on NIH RePORTER: https://reporter.nih.gov/project-details/11100342