**Background**
Hypoxia-inducible factor 1 (HIF-1) plays a critical role in the adaptation of cells to low oxygen environments, which is a hallmark of many solid tumors. HIF-1 consists of α and β subunits that dimerize to regulate the expression of genes involved in angiogenesis, metabolism, and cell survival. Furthermore, the interaction between monocarboxylate transporter 4 (MCT4) and Basigin is essential for lactate transport, supporting the metabolic demands of cancer cells under hypoxic conditions. In addition to oncology, the papain-like protease (PLpro) is a key enzyme for the replication of betacoronaviruses, including SARS-CoV-2. Targeting these pathways provides significant opportunities for treating malignancies and viral infections. In this context, we will introduce a versatile inhibitor – Acriflavine.
**Definition**
Acriflavine (Acriflavinium chloride) hydrochloride is a fluorescent acridine dye and antiseptic agent that acts as a potent HIF-1 inhibitor and PLpro inhibitor. According to the Acriflavine description, it prevents the dimerization of HIF-1α and HIF-1β subunits and inhibits the interaction between MCT4 and Basigin.
**In Vitro and In Vivo Studies**
The Acriflavine biological activity has been demonstrated across various models. Acriflavine in vitro studies show that it inhibits MCT4-Basigin dependent Rluc activity with an IC50 of 4.6 μM and the NhRL-MCT1/Basigin-ChRL interaction with an IC50 of ~19.5 μM. In HSR-GBM1 cells, treatment with 5 μM Acriflavine for 24 hours does not significantly affect hypoxia-induced lactate production, but concentrations of 1-25 μM for 72 hours reduce the clonogenic potential of neurosphere-derived cells, particularly under hypoxia. Regarding antiviral activity, Acriflavine (1-10 μM; 24 h) inhibits SARS-CoV-2 replication in Vero and A549ACE2+ cells; specifically, IC50 values were 64 nM for Vero and 86 nM for A549ACE2+ cells.
Acriflavine In Vivo data further support its efficacy in Acriflavine Cancer research. In NOG mice bearing HSR-GBM1-Luc xenografts, intraperitoneal injection of 8 mg/kg (once daily for 13 or 15 administrations) inhibited tumor growth and reduced microvessel density. In C57BL/6J-CD45.1 mice with BCR/abl-induced chronic myeloid leukemia, 8 mg/kg (i.p.; once daily for 10 days) reduced splenomegaly and the number of leukemia stem cells. Additionally, in K18-ACE2 transgenic mice infected with SARS-CoV-2, oral administration (100 mg/kg) or intramuscular injection (5-15 mg/kg) for 6 days blocked brain infection and reduced pulmonary viral load. In conclusion, Acriflavine is a potent multi-target inhibitor with significant potential in oncology and antiviral therapy.
Keywords
Acriflavine, 69235-50-3, Acriflavinium chloride, Fluorescent Dye, HIF/HIF Prolyl-Hydroxylase, Bacterial, SARS-CoV, Monocarboxylate Transporter, Fungal, Hypoxia-inducible factors, HIFs, HIF-PH, SARS coronavirus, DNA, RNA
References
[1] L M Chan, et al. Interaction of acriflavine with DNA and RNA. J Mol Biol. 1969 Mar 28;40(3):491-5.
[2] Tao Yin, et al. HIF-1 Dimerization Inhibitor Acriflavine Enhances Antitumor Activity of Sunitinib in Breast Cancer Model. Oncol Res. 2015; 22(3): 139-145.
[4] Voss DM, et al. Disruption of the monocarboxylate transporter-4-basigin interaction inhibits the hypoxic response, proliferation, and tumor progression. Sci Rep. 2017 Jun 27;7(1):4292.
[5] Cheloni G, et al. Targeting chronic myeloid leukemia stem cells with the hypoxia-inducible factor inhibitor acriflavine. Blood. 2017 Aug 3;130(5):655-665.
[6] Valeria Napolitano, et al. Acriflavine, a clinically aproved drug, inhibits SARS-CoV-2 and other betacoronaviruses. bioRxiv 2021.03.20.436259.