Anti-FLT3 Monoclonal antibody, clone B3G20 [PerCP-eFluor® 710]

Rationale: The existence of primary and acquired drug resistance is the main obstacle for the effect of multi-kinase inhibitor sorafenib and regorafenib in advanced hepatocellular carcinoma (HCC). However, plenty of patients did not significantly benefit from sorafenib treatment and little is known about the mechanism of drug resistance. Methods: Laser capture microdissection was used to acquire matched normal liver and tumor tissues on formalin-fixed paraffin-embedded specimens collected before sorafenib therapy from the first surgery of 119 HCC patients. Ultra-deep sequencing (similar to 1000x) targeting whole exons of 440 genes in microdissected specimens and siRNA screen in 7 cell lines were performed to find mutations associated with differential responses to sorafenib. Patient-derived xenograft models were employed to determine the role of TPS3 in response to sorafenib. Lentiviruses harboring wild-type and c.G52C-mutant OCT4 were applied to explore the function of OCT4 in resistance to sorafenib. ChIP-PCR assay for analysis of OCT4 transcriptional activity was performed to explore the affinity with the KITLG promoter. Statistical analyses were used to associate levels of p53 and OCT4 with tumor features and patient outcomes. Results: Total 1,050 somatic mutations and 26 significant driver genes were identified. SiRNA screening in 7 HCC cell lines was further performed to identify mutations associated with differential responses to sorafenib. A recurrent nonsynonymous mutation c.G52C in OCT4 (OCT4(mut)) was strongly associated with good response to sorafenib, whereas the stop-gain mutation in TPS3 showed the opposite outcome both in vitro and in vivo. OCT4(wt)-induced stem cell factor (encoded by KITLG gene, SCF) expression and cross-activation of c-KIT/FLT3-BRAF signals were identified indispensably for sorafenib resistance, which could be reversed by the combination of c-KIT tyrosine kinase inhibitors or neutralizing antibody against SCF. Mechanistically, an OCT4 binding site in upstream of KITLG promoter was identified with a higher affinity to wildtype of OCT4 rather than G52C-mutant form, which is indispensable for OCT4-induced expression of KITLG and sorafenib resistance. Conclusion: Our study reported a novel somatic mutation in OCT4 (c.G52C) responsible for the sorafenib effect, and also shed new light on the treatment of HCC through the combination of specific tyrosine kinase inhibitors according to individual genetic patterns.

Toxic retinopathies are most frequently induced by external stimulants (e.g. nicotine, poppers, methanol) and are less frequently undesired side effects of systemic drugs (e.g. hydroxychloroquine, ethambutol, MEK, ERK, FLT3 or checkpoint inhibitors, didanosine, pentosan polysulfate sodium) or intravitreally applied drugs. The clinical symptoms of undesired side effects of drugs are often similar to retinal diseases from other causes, which interferes with the recognition of the undesired side effects of drugs. Clinical findings, pathophysiological mechanisms and if advisable strategies for screening are discussed. The focus is on the presentation of confirmed undesirable side effects with established associations for medications which have long been approved. For novel medications, in addition potential but not proven associations are presented to facilitate the recognition of additional cases with side effects for these medications.