Cytochalasin B

Cytochalasin B is a cell-permeable mycotoxin binding to the barbed end of actin filaments, disrupting the formation of actin polymers, with K_d value of 1.4-2.2 nM for F-actin. Cytochalasin B blocks cell migration. IC50 & Target:Kd: 2.2 nM (F-actin, with Mg²⁺), 1.4 nM (F-actin, with Mg²⁺/K⁺)^[1] In Vitro: Cytochalasin B is a cell-permeable mycotoxin binding to the barbed end of actin filaments, inhibits the enlongation and shortening of actin filaments, with K_ds of 2.2 nM and 1.4 nM for F-actin in the presence of MgCl₂ (2 mM) or MgCl₂ (2 mM) plus KCl, respectively^[1]. Cytochalasin B (0.1-10 μM) shows inhibitory effect on multiple murine cancer cell lines, with IC₅₀s of 2.56 μM (M109c), 10.46 μM (B16BL6), 105.5 μM (P388/ADR), 51.9 μM (P388/S) and IC₈₀s of 12.23 μM (M109c), 44.86 μM (B16BL6), 188.4 μM (P388/ADR), 84.1 μM (P388/S) after treatment for 3 h, with IC₅₀s of 0.25 μM (M109c), 0.37 μM (B16F10), 0.87 μM (B16BL6), and IC₈₀s of 0.75 μM (M109c), 1.21 μM (B16F10), 10.41 μM (B16BL6) after treatment for 4 days^[2]. Cytochalasin B (6 μM) increases the myofibrillar fragmentation index (MFI), which is attributed to the intensely breaking of myofibrillar proteins into short segments. Cytochalasin B also accelerates the disruption of actin filaments. In addition, Cytochalasin B accelerates the transformation from F-actin to G-actin, lowering the content of F-actin and significantly increasing G-actin bands during postmortem conditioning^[3]. In Vivo: Cytochalasin B (10, 25, 50 mg/kg, i.p.) dose-dependently increases the life expectancy of Balb/c mice bearing with P388/ADR leukemias. Cytochalasin B at 50 mg/kg produces 10 % long-term survival in the multidrug resistant P388/ADR cohort, and 40 % long-term survival in the drug sensitive P388/S cohort^[2].