Repurposing Tamoxifen as Potential Host-Directed Therapeutic for Tuberculosis.

The global burden of tuberculosis (TB) is aggravated by the continuously increasing emergence of drug resistance, highlighting the need for innovative therapeutic options. The concept of host-directed therapy (HDT) as adjunctive to classical antibacterial therapy with antibiotics represents a novel and promising approach for treating TB. Here, we have focused on repurposing the clinically used anticancer drug tamoxifen, which was identified as a molecule with strong host-directed activity against intracellular Mycobacterium tuberculosis (Mtb). Using a primary human macrophage Mtb infection model, we demonstrate the potential of tamoxifen against drug-sensitive as well as drug-resistant Mtb bacteria. The therapeutic effect of tamoxifen was confirmed in an in vivo TB model based on Mycobacterium marinum infection of zebrafish larvae. Tamoxifen had no direct antimicrobial effects at the concentrations used, confirming that tamoxifen acted as an HDT drug. Furthermore, we demonstrate that the antimycobacterial effect of tamoxifen is independent of its well-known target the estrogen receptor (ER) pathway, but instead acts by modulating autophagy, in particular the lysosomal pathway. Through RNA sequencing and microscopic colocalization studies, we show that tamoxifen stimulates lysosomal activation and increases the localization of mycobacteria in lysosomes both in vitro and in vivo, while inhibition of lysosomal activity during tamoxifen treatment partly restores mycobacterial survival. Thus, our work highlights the HDT potential of tamoxifen and proposes it as a repurposed molecule for the treatment of TB. IMPORTANCE Tuberculosis (TB) is the world's most lethal infectious disease caused by a bacterial pathogen, Mycobacterium tuberculosis. This pathogen evades the immune defenses of its host and grows intracellularly in immune cells, particularly inside macrophages. There is an urgent need for novel therapeutic strategies because treatment of TB patients is increasingly complicated by rising antibiotic resistance. In this study, we explored a breast cancer drug, tamoxifen, as a potential anti-TB drug. We show that tamoxifen acts as a so-called host-directed therapeutic, which means that it does not act directly on the bacteria but helps the host macrophages combat the infection more effectively. We confirmed the antimycobacterial effect of tamoxifen in a zebrafish model for TB and showed that it functions by promoting the delivery of mycobacteria to digestive organelles, the lysosomes. These results support the high potential of tamoxifen to be repurposed to fight antibiotic-resistant TB infections by host-directed therapy.

Combined chemical genetics and data-driven bioinformatics approach identifies receptor tyrosine kinase inhibitors as host-directed antimicrobials.

Antibiotic resistance poses rapidly increasing global problems in combatting multidrug-resistant (MDR) infectious diseases like MDR tuberculosis, prompting for novel approaches including host-directed therapies (HDT). Intracellular pathogens like Salmonellae and Mycobacterium tuberculosis (Mtb) exploit host pathways to survive. Only very few HDT compounds targeting host pathways are currently known. In a library of pharmacologically active compounds (LOPAC)-based drug-repurposing screen, we identify multiple compounds, which target receptor tyrosine kinases (RTKs) and inhibit intracellular Mtb and Salmonellae more potently than currently known HDT compounds. By developing a data-driven in silico model based on confirmed targets from public databases, we successfully predict additional efficacious HDT compounds. These compounds target host RTK signaling and inhibit intracellular (MDR) Mtb. A complementary human kinome siRNA screen independently confirms the role of RTK signaling and kinases (BLK, ABL1, and NTRK1) in host control of Mtb. These approaches validate RTK signaling as a drugable host pathway for HDT against intracellular bacteria.

The DNA damage-regulated autophagy modulator DRAM1 links mycobacterial recognition via TLR-MYD88 to autophagic defense [corrected].

Autophagy is an important defense mechanism against mycobacteria, the causative agents of tuberculosis. The molecular mechanisms that link mycobacterial recognition to autophagy remain unclear. Our analysis in zebrafish and human macrophage models of mycobacterial infection reveals that the DNA damage-regulated autophagy modulator DRAM1 functions downstream of pathogen recognition by the Toll-like receptor (TLR)/interleukin-1 receptor (IL1R)-MYD88-NF-κB innate immune sensing pathway to activate selective autophagy. Mycobacterial infection of human macrophages and zebrafish embryos induced DRAM1 expression in a MYD88 and NF-κB-dependent manner. DRAM1 knockdown increased mycobacterial infection, whereas overexpression lowered infection by hyperactivating autophagy. DRAM1-mediated selective autophagic defenses require the cytosolic DNA sensor STING and the selective autophagy receptor p62/SQSTM1. Contrary to its known role in autophagy-mediated cell death and cancer, this DRAM1 function is p53 independent. We propose that DRAM1 mediates autophagic defense against a broader range of intracellular pathogens, since DRAM1 expression was also induced by the common bacterial endotoxin lipopolysaccharide.

Nuclear localization of CXCR4 determines prognosis for colorectal cancer patients.

Chemokines and their receptors are implicated in formation of colorectal cancer metastases. Especially CXCR4 is an important factor, determining migration, invasiveness, metastasis and proliferation of colorectal cancer cells. Object of this study was to determine expression of CXCR4 in tumor tissue of colorectal cancer patients and associate CXCR4 expression levels to clinicopathological parameters. Levels of CXCR4 expression of a random cohort of patients, who underwent primary curative resection of a colorectal carcinoma, were retrospectively determined by quantitative real-time RT-PCR and semi-quantitative analyses of immunohistochemical stained paraffin sections. Expression levels were associated to clinicopathological parameters. Using RT-PCR we found that a high expression of CXCR4 in the primary tumor was an independent prognostic factor for a poor disease free survival (p = 0.03, HR: 2.0, CI = 1.1-3.7). Immunohistochemical staining showed that nuclear distribution of CXCR4 in the tumor cells was inversely associated with disease free and overall survival (p = 0.04, HR: 2.6, CI = 1.0-6.2), while expression in the cytoplasm was not associated with prognosis. In conclusion, our study showed that a high expression of nuclear localized CXCR4 in tumor cells is an independent predictor for poor survival for colorectal cancer patients.