Inhibiting checkpoint kinase 1 protects bone from bone resorption by mammary tumor in a mouse model

Abstract

DNA damage response plays a critical role in tumor growth, but little is known about its potential role in bone metabolism. We employed selective inhibitors of Chk1 and examined their effects on the proliferation and migration of mammary tumor cells as well as the development of osteoblasts and osteoclasts. Further, using a mouse model of bone metastasis we evaluated the effects of Chk1 inhibitors on bone quality. Chk1 inhibitors blocked the proliferation, survival, and migration of tumor cells in vitro and suppressed the development of bone-resorbing osteoclasts by downregulating NFATc1. In the mouse model, Chk1 inhibitor reduced osteolytic lesions and prevented mechanical weakening of the femur and tibia. Analysis of RNA-seq expression data indicated that the observed effects were mediated through the regulation of eukaryotic translation initiation factor 2 alpha, stress to the endoplasmic reticulum, S100 proteins, and bone remodeling-linked genes. Our findings suggest that targeting Chk1 signaling without adding DNA damaging agents may protect bone from degradation while suppressing tumor growth and migration.

Effects of a checkpoint kinase inhibitor, AZD7762, on tumor suppression and bone remodeling

“…While the present results revealed a novel role for AZD7762 in bone remodeling and bone metastasis, the present study has certain limitations. The experiments herein employed mouse and human cell lines ( 11 ), and gene expression was primarily examined using monolayer cell cultures. Although clinical trials of AZD7762 are not going forward due to unpredictable cardiac toxicity, inhibition of Chk remains an important therapeutic target ( 38 ).…”

“…AZD7762 is a potent inhibitor of Chk1 and Chk2 that potentiates antitumor activity in xenograft models in a dose-dependent manner when simultaneously administered with DNA-damaging agents ( 9 ). PD407824 is a selective inhibitor of Chk1 ( 10 ), and its inhibitory effect on tumor growth and bone resorption was recently reported in connection to the regulation of stress in the endoplasmic reticulum (ER) ( 11 ). Chk1 is a primary gatekeeper of cell division at multiple cell cycle checkpoints, including the S, G2/M and M phases.…”

“…The responses to AZD7762 and PD407824 were examined in monolayer cell cultures, three-dimensional (3D) spheroids ( 21 ), and 3D bio-printed bone constructs ( 22 ). While PD407824 is able to inhibit tumor growth and osteoclastogenesis, its ability to promote osteoblast development is limited ( 11 ). It has been reported that inhibition of Chk2, and not Chk1, downregulates p53 expression ( 23 ).…”

Finite Element Analysis of the Mouse Distal Femur with Tumor Burden in Response to Knee Loading

“…While the effects of Chk1 inhibitors on tumor cells have been reported (18), their role in development of bone-forming osteoblasts and bone-resorbing osteoclasts need to be examined. In our previous study, we conducted in vitro and in vivo analysis for evaluating the role of PD407824 on MC3T3 osteoblast-like cells as well as RAW264.7 pre-osteoclast cells and found that PD407824 is an effective inhibitor of bone degradation in addition to its anti-tumor effects (14). The current study further supports its potential benefit in preserving bone mechanical properties from degradation by metastatic tumor.…”

“…Activation of Chk1 results in cell cycle arrest, and its mutations are reported to be linked to breast and other cancers (11). Administration of Chk inhibitors for inhibiting tumor growth has been considered (12, 13), and we recently reported the effects of these inhibitors on suppression of bone resorption (14). In this report, we showed that Chk1 inhibitors blocked the proliferation, survival, and migration of tumor cells in vitro and suppressed the development of bone-resorbing osteoclasts by downregulating nuclear factor of activated T cells (NFATc1), a master transcription factor for osteoclast development.…”