Multiple myeloma (MM) is still incurable and characterized by clonal expansion of plasma cells in the bone marrow (BM). Therefore, effective therapeutic interventions must target both myeloma cells and the BM niche. Cell proliferation, drug resistance, and chromosomal instability (CIN) induced by CHEK1 were confirmed by Giemsa staining, exon sequencing, immunofluorescence and xenograft model in vivo. Bone lesion was evaluated by Tartrate-resistant acid phosphatase (TRAP) staining. The existence of circCHEK1_246aa was evaluated by qPCR, Sanger sequencing and Mass Spectrometer. We demonstrated that CHEK1 expression was significantly increased in human MM samples relative to normal plasma cells, and that in MM patients, high CHEK1 expression was associated with poor outcomes. Increased CHEK1 expression induced MM cellular proliferation and evoked drug-resistance in vitro and in vivo. CHEK1-mediated increases in cell proliferation and drug resistance were due in part to CHEK1-induced CIN. CHEK1 activated CIN, partly by phosphorylating CEP170. Interestingly, CHEK1 promoted osteoclast differentiation by upregulating NFATc1 expression. Intriguingly, we discovered that MM cells expressed circCHEK1_246aa, a circular CHEK1 RNA, which encoded and was translated to the CHEK1 kinase catalytic center. Transfection of circCHEK1_246aa increased MM CIN and osteoclast differentiation similarly to CHEK1 overexpression, suggesting that MM cells could secrete circCHEK1_246aa in the BM niche to increase the invasive potential of MM cells and promote osteoclast differentiation. Our findings suggest that targeting the enzymatic catalytic center encoded by CHEK1 mRNA and circCHEK1_246aa is a promising therapeutic modality to target both MM cells and BM niche.

中文翻译：

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CHEK1 和 circCHEK1_246aa 在多发性骨髓瘤中引起染色体不稳定并诱导骨病变形成

多发性骨髓瘤 (MM) 仍然无法治愈，其特点是骨髓 (BM) 中浆细胞的克隆性扩增。因此，有效的治疗干预措施必须同时针对骨髓瘤细胞和 BM 生态位。通过吉姆萨染色、外显子测序、免疫荧光和体内异种移植模型证实了由 CHEK1 诱导的细胞增殖、耐药性和染色体不稳定性 (CIN)。通过抗酒石酸酸性磷酸酶 (TRAP) 染色评估骨损伤。通过qPCR、Sanger测序和质谱仪评估circCHEK1_246aa的存在。我们证明，相对于正常浆细胞，人类 MM 样本中的 CHEK1 表达显着增加，并且在 MM 患者中，高 CHEK1 表达与不良结果相关。增加的CHEK1表达诱导MM细胞增殖并在体外和体内诱发耐药性。CHEK1 介导的细胞增殖和耐药性增加部分是由于 CHEK1 诱导的 CIN。CHEK1 激活 CIN，部分通过磷酸化 CEP170。有趣的是，CHEK1 通过上调 NFATc1 表达促进破骨细胞分化。有趣的是，我们发现 MM 细胞表达 circCHEK1_246aa，一种环状 CHEK1 RNA，它编码并翻译到 CHEK1 激酶催化中心。转染circCHEK1_246aa 增加MM CIN 和破骨细胞分化，类似于CHEK1 过表达，表明MM 细胞可以在BM 生态位中分泌circCHEK1_246aa 以增加MM 细胞的侵袭潜力并促进破骨细胞分化。