ML216 is a potent, selective, and cell-permeable inhibitor of Bloom syndrome protein (BLM) helicase with IC50 values of 2.98μM for full-length BLM and 0.97μM for BLM636-1298[1]. ML216 competitively interferes with BLM binding to deoxyribonucleic acid (DNA), inhibits BLM-dependent DNA unwinding and single-stranded DNA (ssDNA)-dependent adenosine triphosphatase (ATPase) activity, and perturbs homologous recombination (HR) repair and chromosome stability[1,2]. ML216 is used in research on DNA-damage repair, replication stress, chromosome stability, cellular senescence, tumor-cell sensitization to DNA-damaging agents, and xenograft responses[1,3,4,5,6,7].
In vitro, ML216 (12.5μM and 50μM; 24h, 48h, and 72h) concentration- and time-dependently reduced the proliferation of BLM-complemented PSNF5 fibroblasts while exerting minimal effects on BLM-deficient PSNG13 fibroblasts[1]. ML216 (50μM; 36h) increased sister chromatid exchange (SCE) frequency in PSNF5 cells without significantly changing SCE frequency in PSNG13 cells[2]. ML216 (10μM) combined with cisplatin (CDDP; 1μM; 48h) reduced PC3 prostate cancer cell proliferation, increased phosphorylated histone H2AX (γH2AX) foci and cleaved caspase-3, activated checkpoint kinase 1 (Chk1) and checkpoint kinase 2 (Chk2), and increased apoptosis[3]. ML216 (10μM; 24h) with 8Gy irradiation reduced RAD51 recombinase (RAD51) foci, increased phosphorylated DNA-dependent protein kinase catalytic subunit (pDNA-PKcs), and delayed DNA double-strand break (DSB) repair in H460, H1299, and A549 non-small cell lung cancer (NSCLC) cells[4]. ML216 (0.78125μM, 1.5625μM, 3.125μM, 6.25μM, 12.5μM, and 25μM) combined with melphalan (0.78125μM, 1.5625μM, 3.125μM, 6.25μM, 12.5μM, 25μM, and 50μM; 4 days) reduced proliferation and increased apoptosis and DNA damage in XG19, XG2, and XG1 multiple myeloma cells[5]. ML216 (50μM) combined with etoposide (100μM; 24h) strengthened deleted in breast cancer 1 (DBC1)-BLM interaction, preserved cellular BLM, and reduced p21 induction in HEK293T cells[6]. ML216 (5μM) combined with olaparib (40μM; 48h) reduced PC3 cell viability, proliferation, clonogenic growth, migration, and invasion[7].
In vivo, ML216 (1mg/kg; intraperitoneal injection twice weekly for 5 weeks) reduced pulmonary senescence and fibrosis and improved pulmonary function in 22-month-old mice[6]. ML216 (15mg/kg) combined with olaparib (30mg/kg; intraperitoneal injection three times weekly for 3 weeks) reduced tumor volume, tumor weight, and Ki-67 expression in male BALB/c nude mice bearing PC3 xenografts[7].
References:[1] Nguyen GH, Dexheimer TS, Rosenthal AS, Chu WK, Singh DK, Mosedale G, et al. A small molecule inhibitor of the BLM helicase modulates chromosome stability in human cells. Chem Biol. 2013;20(1):55-62. doi:10.1016/j.chembiol.2012.10.016.
[2] Rosenthal AS, Dexheimer TS, Gileadi O, Nguyen GH, Chu WK, Hickson ID, et al. Synthesis and SAR studies of 5-(pyridin-4-yl)-1,3,4-thiadiazol-2-amine derivatives as potent inhibitors of Bloom helicase. Bioorg Med Chem Lett. 2013;23(20):5660-5666. doi:10.1016/j.bmcl.2013.08.025.
[3] Ma XY, Zhao JF, Ruan Y, Zhang WM, Xu HQ. ML216-induced BLM helicase inhibition sensitizes PCa cells to the DNA-crosslinking agent cisplatin. Molecules. 2022;27(24):8790. doi:10.3390/molecules27248790.
[4] Kong Y, Xu C, Sun X, Sun H, Zhao X, He N, et al. BLM helicase inhibition synergizes with PARP inhibition to improve the radiosensitivity of olaparib-resistant non-small cell lung cancer cells by inhibiting homologous recombination repair. Cancer Biol Med. 2022;19(8):1150-1171. doi:10.20892/j.issn.2095-3941.2021.0178.
[5] Ovejero S, Viziteu E, Dutrieux L, Devin J, Lin YL, Alaterre E, et al. The BLM helicase is a new therapeutic target in multiple myeloma involved in replication stress survival and drug resistance. Front Immunol. 2022;13:983181. doi:10.3389/fimmu.2022.983181.
[6] Cui F, Han X, Zhang X, Wang S, Liang N, Tan Q, et al. ML216 prevents DNA damage-induced senescence by modulating DBC1-BLM interaction. Cells. 2023;12(1):145. doi:10.3390/cells12010145.
[7] Huang M, Chen L, Guo Y, Ruan Y, Xu H. PARP1 negatively regulates transcription of BLM through its interaction with HSP90AB1 in prostate cancer. J Transl Med. 2023;21(1):445. doi:10.1186/s12967-023-04288-z.