GSE192359
Cucurbitacin B-induced G2/M cell cycle arrest of conjunctival melanoma cells mediated by GRP78-FOXM1-KIF20A pathway
Conjunctival melanoma (CM) is a rare and fatal malignant eye tumor, it is life-threatening, mainly because of the lack of diagnostic biomarkers or drug access. In this study, we deciphered a novel anti-CM mechanism of a natural tetracyclic compound isolated from a Cucurbitaceae family plant and named as Cucurbitacin B (CuB). We found that CuB remarkably inhibited the proliferation of CRMM2 cells at a submicromolar level (IC50=0.15 µM) without toxicity to normal cells via G2/M cell cycle arrest and subsequent cell apoptosis. RNA-seq screening identified the Kinesin family member 20A (KIF20A) as a key gene which was abolished by the CuB treatment and proved to be a downstream effector of FOXM1 pathway. Further target identification by the activity-based protein profiling (ABPP) chemoproteomic approach revealed that 78 KDa Glucose-Regulated Protein (GRP78) is a potential target of CuB. Several lines of evidence demonstrated that CuB interacted with GRP78 and bound with a Kd value of 0.11 µM. Furthermore, functional experiments showed that CuB suppressed the ATPase activity of GRP78 both in human recombinant GRP78 and cellular lysates. Knockdown of the GRP78 gene significantly induced the downregulation of FOXM1 and related pathway genes including KIF20A, underlying an interesting therapeutic perspective. Taken together, our current work proved a substantial therapeutic potential of the traditional medicine CuB, and it needs to be explored further for future CM therapies. Overall design: Examination of CuB (0.1 µM & 0.2 µM) treatment and control samples in CRMM2 cells by RNA-seq, in triplicate.