Doxycycline (calcium)

Doxycycline calcium is an orally active highly lipophilic, tissue-permeable MMP inhibitor with broad-spectrum antibacterial activity. Doxycycline calcium is also a semi-synthetic antibiotic with chelating properties, which blocks bacterial protein synthesis and inhibits extracellular matrix degradation through interactions with zinc and calcium atoms. Doxycycline calcium also inhibits mitochondrial biogenesis, translation, and the expression of respiratory chain proteins. Doxycycline calcium induces apoptosis, inhibits autophagy and EMT, downregulates stem cell markers, and activates the PI3K-AKT pathway, thereby effectively inhibiting the viability and proliferation of cancer cells such as breast cancer cells. Doxycycline calcium also promotes the survival and self-renewal of embryonic stem cells and neural stem cells, and reduces the frequency of medium changes in culture. Doxycycline calcium has been applied in studies related to breast cancer, prostate cancer, bladder cancer, and other cancers^{[1][2][3][4][5]}. In Vitro:Doxycycline (11.39 μM + MCF-7; 7.13 μM + MDA-MB-468; 72 h) calcium significantly reduces the population of CD44⁺/CD24^-/low breast cancer stem cells in MCF-7 and MDA-MB-468 cells^[2].
Doxycycline (11.39 μM+MCF-7; 7.13 μM+MDA-MB-468; 72 h) calcium significantly downregulates the mRNA and protein expression of stem cell markers (Nanog, Oct4, Sox2, c-Myc, CD44) in MCF-7 and MDA-MB-468 breast cancer cells^[2].
Doxycycline (1 μg/mL; 5 d) calcium increases the colony formation efficiency of undifferentiated human embryonic stem cells (H9, HSF6, H1, H7, HUES6) and human induced pluripotent stem cells (retrovirus-derived, lentivirus-derived, protein-induced lines), and elevates the number of colonies expressing undifferentiated markers under various culture conditions^[3].
Doxycycline (1 μg/mL; 5 d) calcium promotes the survival and proliferation of H9 human embryonic stem cells (hESC) more effectively than Y-27632 (HY-10071), resulting in larger cell colonies, a higher proportion of undifferentiated AP⁺ cells, as well as downregulated expression of pro-apoptotic genes and upregulated expression of pluripotency-related genes^[3].
Doxycycline (1 μg/mL; 6 d; passage 12) calcium reduces cell apoptosis, increases S-phase cell accumulation, supports the long-term expansion of H9 human embryonic stem cells (H9 hESCs) and Lenti-1 induced pluripotent stem cells (Lenti-1 hiPSCs) cultured in clusters on MEF feeder layers, and maintains the pluripotency and normal karyotype of the cells during repeated passaging^[3].
Doxycycline (1 μg/mL; 7 d) calcium maintains the viability, proliferation and expression of undifferentiated markers of H9 human embryonic stem cells for up to 7 days without medium change, and reduces apoptotic cell death of newly seeded dissociated cells and preformed cell clusters within 3 days without medium change^[5].
Doxycycline (1 μg/mL; 30-72 d) calcium supports long-term subculture of H9, HSF6 human embryonic stem cells as well as Retro-1, Lenti-1, Pro-1 human induced pluripotent stem cells. The culture medium is replaced every 3 days, and the growth rate remains consistent with that under the standard daily medium change condition during passages 5 to 12^[5].
Doxycycline (1 μg/mL; 72 d) calcium maintains normal karyotype, expression of undifferentiated markers and pluripotency (the ability to differentiate into all cells of the three germ layers in vitro) of H9 human embryonic stem cells that are subcultured 12 times with medium replacement every 3 days^[5]. In Vivo:Doxycycline (25-50 mg/kg; p.o.; twice daily; 10 days) calcium exerts dose-dependent toxic effects on male Wistar rats: a dosage of 50 mg/kg twice daily for 10 consecutive days causes 30% mortality, cardiomyopathy, and significant elevation of biomarkers for muscle and cardiac injury; whereas a dosage of 25 mg/kg twice daily for 10 consecutive days only induces mild skeletal muscle injury without cardiac toxicity^[1].
Doxycycline (60 mg/kg; intraperitoneal injection; once daily for 15 consecutive days) calcium significantly inhibits the growth of CD44v9-expressing prostate cancer xenografts by reducing the proliferation of CD44v9-positive cells^[4].
Supplementary culture of H9 human embryonic stem cells (H9 hESCs) with Doxycycline (1 μg/mL; medium changed every 3 days; up to passage 12) calcium maintains their pluripotency and enables in vivo teratoma formation, which contains all three embryonic germ layers^[5].

Note:
Please do not refer to only one article to determine the experimental conditions. It is recommended to determine the optimal experimental conditions (animal strain, age, dosage, frequency and cycle, detection time and indicators, etc.) through preliminary experiments before the formal experiment.