When
Presenter:
Dr. Steven Johnson
Associate Professor, Biochemistry & Molecular Biology, Indiana University School of Medicine
Abstract:
Cancer remains the second leading cause of death in the US, highlighting the need for new therapeutic strategies. Proteasome inhibitors have demonstrated the potential of targeting protein homeostasis pathways for cancer treatment, and molecular chaperones, particularly heat shock proteins (HSPs), are central to these pathways, assisting in protein folding and degradation. Abnormal expression and function of HSPs are linked to cancer progression and treatment resistance, driving interest in developing HSP inhibitors. While initial drug development efforts focused on the HSP90 and HSP70 families, the HSP60 chaperonin system remained largely unexplored, despite its association with tumor progression, metastasis, and poor clinical outcomes. In healthy cells, HSP60 is localized to mitochondria to support protein folding, but in cancer cells, it is often over- expressed and mis-localized, accumulating outside mitochondria. This dysregulation makes HSP60 a promising therapeutic target as it is hypothesized to be an exploitable vulnerability allowing the selective targeting of cancer over non-cancer cells. In this seminar, I will provide an overview of HSP60 structure and function, its dysregulation in cancer, and the rationale for targeting it therapeutically, while highlighting our multidisciplinary approach to validating HSP60 as a chemotherapeutic target.
Our research has identified several structural classes of HSP60 inhibitors that selectively induce apoptosis in colorectal cancer cells while exhibiting low toxicity to non-cancer cells. These inhibitors also suppress cancer cell migration and clonogenicity in vitro, and screening against the NCI panel of cancer cell lines has demonstrated their potential as broad-spectrum anti-cancer agents. To better understand the mechanisms of these inhibitors, we are developing cell lines with EYFP and mCherry fluorophores localized to mitochondria and cytosol, serving as reporters for HSP60-mediated folding processes. While preliminary results suggest HSP60 engagement in mitochondria and/or the cytosol, further studies are underway to confirm on-target inhibition. We are using cryo-electron microscopy (cryoEM) and proteomics to identify inhibitor binding sites, followed by the generation of point mutations in chaperonins that confer resistance to inhibition. These studies have already validated on-target effects in E. coli, and we are extending this work to human cancer cells to further confirm mechanisms. Additionally, we have initiated in vivo studies to evaluate the ADME-tox profiles and chemotherapeutic efficacy of our lead candidates in mouse colon cancer models. Together, these efforts are advancing the potential of HSP60-targeted therapies, laying the groundwork for developing new treatments for a broad range of cancers.
Hosted by: Dr. Marielle Hegetschweiler/Walti