Doxycycline, an Inhibitor of Mitochondrial Biogenesis, Effectively Reduces Cancer Stem Cells (CSCs) in Early Breast Cancer Patients: A Clinical Pilot Study

Abstract

Background and objectives: Cancer stem cells (CSCs) have been implicated in tumor initiation, recurrence, metastatic spread and poor survival in multiple tumor types, breast cancers included. CSCs selectively overexpress key mitochondrial-related proteins and inhibition of mitochondrial function may represent a new potential approach for the eradication of CSCs. Because mitochondria evolved from bacteria, many classes of FDA-approved antibiotics, including doxycycline, actually target mitochondria. Our clinical pilot study aimed to determine whether short-term pre-operative treatment with oral doxycycline results in reduction of CSCs in early breast cancer patients.Methods: Doxycycline was administered orally for 14 days before surgery for a daily dose of 200 mg. Immuno-histochemical analysis of formalin-fixed paraffin-embedded (FFPE) samples from 15 patients, of which 9 were treated with doxycycline and 6 were controls (no treatment), was performed with known biomarkers of “stemness” (CD44, ALDH1), mitochondria (TOMM20), cell proliferation (Ki67, p27), apoptosis (cleaved caspase-3), and neo-angiogenesis (CD31). For each patient, the analysis was performed both on pre-operative specimens (core-biopsies) and surgical specimens. Changes from baseline to post-treatment were assessed with MedCalc 12 (unpaired t-test) and ANOVA.Results: Post-doxycycline tumor samples demonstrated a statistically significant decrease in the stemness marker CD44 (p-value < 0.005), when compared to pre-doxycycline tumor samples. More specifically, CD44 levels were reduced between 17.65 and 66.67%, in 8 out of 9 patients treated with doxycycline. In contrast, only one patient showed a rise in CD44, by 15%. Overall, this represents a positive response rate of nearly 90%. Similar results were also obtained with ALDH1, another marker of stemness. In contrast, markers of mitochondria, proliferation, apoptosis, and neo-angiogenesis, were all similar between the two groups.Conclusions: Quantitative decreases in CD44 and ALDH1 expression are consistent with pre-clinical experiments and suggest that doxycycline can selectively eradicate CSCs in breast cancer patients in vivo. Future studies (with larger numbers of patients) will be conducted to validate these promising pilot studies.

Inhibition of Metabolic Shift can Decrease Therapy Resistance in Human High-Grade Glioma Cells

“…This finding confirms that OXPHOS co-targeting could be another good option in the future as it has been suggested in Gboxin therapy or other antibiotics targeting mitochondrial functions (e.g. doxycycline) [36,37].…”

Mitochondria as target to inhibit proliferation and induce apoptosis of cancer cells: the effects of doxycycline and gemcitabine

“…We reported that patients with tumours of the nasopharynx and larynx who were treated with tetracyclines to prevent secondary bacterial infections survived longer than patients treated with erythromycin 30 . In a more recent clinical pilot study of breast cancer patients, pre-operative treatment with doxycycline decreased the expression of the stemness markers CD44 and ALDH1 in tumour biopsies, consistent with the view that doxycycline eliminates cancer stem cells in vivo 31 .…”

Oxidative phosphorylation as a potential therapeutic target for cancer therapy

“…Thus, tigecycline, an inhibitor of mitochondrial protein synthesis, selectively eradicates chronic myeloid leukemia stem cells both in vitro and in vivo , in xenograft models, if it is combined with imatinib, the tyrosine kinase inhibitor used to treat chronic myeloid leukemia . Moreover, doxycycline has been used in a clinical pilot trial for the preoperative treatment of early breast cancer patients, leading to a statistically significant decrease in the stemness markers aldehyde dehydrogenase 1 and CD44 . This type of results has led to the suggestion that tetracyclines may specifically target cancer stem cells and hence could be “repurposed” for the treatment of neoplastic diseases …”

“…12 Moreover, doxycycline has been used in a clinical pilot trial for the preoperative treatment of early breast cancer patients, leading to a statistically significant decrease in the stemness markers aldehyde dehydrogenase 1 and CD44. 25 This type of results has led to the suggestion that tetracyclines may specifically target cancer stem cells and hence could be "repurposed" for the treatment of neoplastic diseases. 26 Cationic lipophils.…”