Ablation of VLA4 in multiple myeloma cells redirects tumor spread and prolongs survival

Deep Hathi,Kathleen Duncan,Chantiya Chanswangphuwana,Walter J Akers,Michael Rettig,Anchal Ghai,Dolonchampa Maji,Francesca Fontana,Julie Ritchey,Nicholas Cho,Julie O’Neal,John F Dipersio,Ravi Vij,Monica Shokeen,Mark Fiala

doi:10.1038/s41598-021-03748-0

Abstract

Multiple myeloma (MM) is a cancer of bone marrow (BM) plasma cells, which is increasingly treatable but still incurable. In 90% of MM patients, severe osteolysis results from pathological interactions between MM cells and the bone microenvironment. Delineating specific molecules and pathways for their role in cancer supportive interactions in the BM is vital for developing new therapies. Very Late Antigen 4 (VLA4, integrin α4β1) is a key player in cell–cell adhesion and signaling between MM and BM cells. We evaluated a VLA4 selective near infrared fluorescent probe, LLP2A-Cy5, for in vitro and in vivo optical imaging of VLA4. Furthermore, two VLA4-null murine 5TGM1 MM cell (KO) clones were generated by CRISPR/Cas9 knockout of the Itga4 (α4) subunit, which induced significant alterations in the transcriptome. In contrast to the VLA4+ 5TGM1 parental cells, C57Bl/KaLwRij immunocompetent syngeneic mice inoculated with the VLA4-null clones showed prolonged survival, reduced medullary disease, and increased extramedullary disease burden. The KO tumor foci showed significantly reduced uptake of LLP2A-Cy5, confirming in vivo specificity of this imaging agent. This work provides new insights into the pathogenic role of VLA4 in MM, and evaluates an optical tool to measure its expression in preclinical models.

Highlights

Multiple myeloma (MM) is a cancer of bone marrow (BM) plasma cells, which is increasingly treatable but still incurable
About 60% of MM patients will suffer a fracture during the disease course despite treatment, with the severity of bone lesions serving as an independent predictor of survival in MM p atients[6]
The activated form of VLA4 binds with high affinity to the ligands, fibronectin and vascular cell adhesion molecule-1 (VCAM-1) expressed on BM stromal cells, increasing myeloma cell adhesion and survival within the BM microenvironment[11,12]

Summary

Introduction

Multiple myeloma (MM) is a cancer of bone marrow (BM) plasma cells, which is increasingly treatable but still incurable. In addition to the cell autonomous factors such as high-risk cytogenetics, the bone marrow (BM) microenvironment is co-opted by myeloma cells for homing, survival, and acquiring drug resistance. The dynamic of interactions between myeloma cells and the microenvironmental factors fosters their ability to grow, home to new sites, escape immune surveillance and resist chemotherapy. In myeloma carcinogenesis, the Very Late Antigen 4 (VLA4, CD49d/CD29, integrin α4β1) is a front-runner implicated in myeloma cell homing, survival and acquisition of cell-adhesion mediated drug resistance (CAMDR). The activated form of VLA4 binds with high affinity to the ligands, fibronectin and VCAM-1 expressed on BM stromal cells, increasing myeloma cell adhesion and survival within the BM microenvironment[11,12]. The interaction between VLA4 on myeloma cells and VCAM-1 in the bone microenvironment reduces osteoblastogenesis, increases osteoclastogenesis and promotes myeloma bone disease[13,14,15,16,17]

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Results

Conclusion