Effects of doxycycline on human prostate cancer cells in vitro

Repurposing approved non-oncology drugs for cancer therapy: a comprehensive review of mechanisms, efficacy, and clinical prospects

Cancer poses a significant global health challenge, with predictions of increasing prevalence in the coming years due to limited prevention, late diagnosis, and inadequate success with current therapies. In addition, the high cost of new anti-cancer drugs creates barriers in meeting the medical needs of cancer patients, especially in developing countries. The lengthy and costly process of developing novel drugs further hinders drug discovery and clinical implementation. Therefore, there has been a growing interest in repurposing approved drugs for other diseases to address the urgent need for effective cancer treatments. The aim of this comprehensive review is to provide an overview of the potential of approved non-oncology drugs as therapeutic options for cancer treatment. These drugs come from various chemotherapeutic classes, including antimalarials, antibiotics, antivirals, anti-inflammatory drugs, and antifungals, and have demonstrated significant antiproliferative, pro-apoptotic, immunomodulatory, and antimetastatic properties. A systematic review of the literature was conducted to identify relevant studies on the repurposing of approved non-oncology drugs for cancer therapy. Various electronic databases, such as PubMed, Scopus, and Google Scholar, were searched using appropriate keywords. Studies focusing on the therapeutic potential, mechanisms of action, efficacy, and clinical prospects of repurposed drugs in cancer treatment were included in the analysis. The review highlights the promising outcomes of repurposing approved non-oncology drugs for cancer therapy. Drugs belonging to different therapeutic classes have demonstrated notable antitumor effects, including inhibiting cell proliferation, promoting apoptosis, modulating the immune response, and suppressing metastasis. These findings suggest the potential of these repurposed drugs as effective therapeutic approaches in cancer treatment. Repurposing approved non-oncology drugs provides a promising strategy for addressing the urgent need for effective and accessible cancer treatments. The diverse classes of repurposed drugs, with their demonstrated antiproliferative, pro-apoptotic, immunomodulatory, and antimetastatic properties, offer new avenues for cancer therapy. Further research and clinical trials are warranted to explore the full potential of these repurposed drugs and optimize their use in treating various cancer types. Repurposing approved drugs can significantly expedite the process of identifying effective treatments and improve patient outcomes in a cost-effective manner.

Doxycycline-Induced Changes in Circulating MMP or TIMP2 Levels Are Not Associated with Skeletal-Related Event-Free or Overall Survival in Patients with Bone Metastases from Breast Cancer

Doxycycline is often used as a promoter of inducible gene expression in preclinical models; however, it can also have direct effects on tumor growth and survival. This is due in part to its ability to inhibit cell invasion and regulate matrix metalloproteinase (MMP) expression. Given that doxycycline is also osteotropic, a clinical study to assess its effects on modulation of tumor progression or prevention of skeletal-related events (SRE) in patients with bone metastases from breast cancer (the Achilles trial) was undertaken. Patients received 100 mg of oral doxycycline twice daily for 12 weeks, with serum obtained at baseline and 4, 8 and 12 weeks post-initiation of doxycycline treatment. Exploratory analysis of the effects of doxycycline on circulating levels of MMP or tissue inhibitor of matrix metalloproteinase 2 (TIMP2) was performed in enrolled patients. Statistically significant associations were observed between MMP2, MMP9 and TIMP2 at baseline with significant associations maintained between absolute levels and changes in levels of MMP2 and TIMP2 at weeks 4-12 post initiation of doxycycline. Treatment with doxycycline generally resulted in decreases in MMP2 and MMP9 levels with concurrent upregulation of TIMP2 at 12 weeks post-initiation of doxycycline treatment. Despite this, we observed no association with the levels of any of these factors with either SRE-free or overall survival in this patient cohort. In summary, despite observing hypothesized effects of doxycycline administration on surrogate markers of its anti-tumor activity, measures of circulating levels of these biomarkers were not prognostic in this patient population.

Repurposed Drugs in Gastric Cancer

Gastric cancer (GC) is one of the major causes of death worldwide, ranking as the fifth most incident cancer in 2020 and the fourth leading cause of cancer mortality. The majority of GC patients are in an advanced stage at the time of diagnosis, presenting a poor prognosis and outcome. Current GC treatment approaches involve endoscopic detection, gastrectomy and chemotherapy or chemoradiotherapy in an adjuvant or neoadjuvant setting. Drug development approaches demand extreme effort to identify molecular mechanisms of action of new drug candidates. Drug repurposing is based on the research of new therapeutic indications of drugs approved for other pathologies. In this review, we explore GC and the different drugs repurposed for this disease.

Doxycycline Hydrochloride Regulates Cytoskeletal Rearrangement and Epithelial-To-Mesenchymal Transition in Malignant Rhabdoid Tumour of the Kidney

Objective. As a highly malignant tumour, malignant rhabdoid tumours of the kidney (MRTK) are prone to metastasis and invasion, while tumour metastasis and invasion are inseparable from matrix metalloproteinases (MMPs) and epithelial-mesenchymal transformation (EMT). Moreover, the key to EMT is remodelling of the cytoskeleton. Therefore, our study is aimed at investigating whether doxycycline hydrochloride (DCH), an inhibitor of MMPs, could reverse EMT in MRTK to exert an antitumour effect by regulating MMPs and the cytoskeleton. Methods. The existence of EMT in MRTK cells was verified by bioinformatics analysis, immunofluorescence, and western blotting (WB). In vitro, the proliferation, migration, and invasion abilities of G401 cells were examined by Cell Counting Kit-8 (CCK-8), scratch, and Transwell assays, respectively. The effect of DCH on tumour growth in tumour-bearing mice was explored in in vivo experiments, and the expression of MMP2 and MMP9 and EMT correlation indexes was measured by immunofluorescence and WB, and the changes in cytoskeletal F-actin and β-tubulin were measured by fluorescence. Results. The altered extracellular matrix (ECM) composition, EMT, and high expression of MMP2 and MMP9 existed in MRTK. DCH inhibited the proliferation, migration, and invasion of G401 cells in vitro. In vivo, DCH inhibited tumour growth in mice, downregulated the expression of MMP2 and MMP9, and partially reversed EMT. Alternatively, DCH resulted in cytoskeletal rearrangements of G401 cells. Conclusions. DCH, as an MMP inhibitor, is used for the first time in MRTK research, showing good antitumour effects by reversing EMT and potentially providing new therapeutic measures for MRTK treatment.

Doxycycline Changes the Transcriptome Profile of mIMCD3 Renal Epithelial Cells

Tetracycline-inducible gene expression systems have been used successfully to study gene function in vivo and in vitro renal epithelial models but the effects of the common inducing agent, doxycycline (DOX), on gene expression are not well appreciated. Here, we evaluated the DOX effects on the transcriptome of a widely used renal epithelial cell model, mIMCD3 cells, to establish a reference. Cells were grown on permeable filter supports in the absence and presence of DOX (3 or 6 days), and genome-wide transcriptome profiles were assessed using RNA-Seq. We found DOX significantly altered the transcriptome profile, changing the abundance of 1,549 transcripts at 3 days and 2,643 transcripts at 6 days. Within 3 days of treatment, DOX significantly decreased the expression of multiple signaling pathways (ERK, cAMP, and Notch) that are associated with cell proliferation and differentiation. Genes associated with cell cycle progression were subsequently downregulated in cells treated with DOX for 6 days, as were genes involved in cellular immune response processes and several cytokines and chemokines, correlating with a remarkable repression of genes encoding cell proliferation markers. The results provide new insight into responses of renal epithelial cells to DOX and a establish a resource for DOX-mediated gene expression systems.

Doxycycline Attenuates Cancer Cell Growth by Suppressing NLRP3-Mediated Inflammation

NLR family pyrin domain containing 3 (NLRP3) inflammasome formation is triggered by the damaged mitochondria releasing reactive oxygen species. Doxycycline was shown to regulate inflammation; however, its effect on NLRP3 in cancer remains largely unknown. Therefore, we sought to determine the effect of doxycycline on NLRP3 regulation in cancer using an in vitro model. NLRP3 was activated in a prostate cancer cell line (PC3) and a lung cancer cell line (A549) before treatment with doxycycline. Inflammasome activation was assessed by analyzing RNA expression of NLRP3, Pro-CASP-1, and Pro-IL1β using RT-qPCR. Additionally, NLPR3 protein expression and IL-1β secretion were analyzed using Western blot and ELISA, respectively. Tumor cell viability was determined using Annexin V staining and a cell proliferation assay. Cytokine secretion was analyzed using a 41Plex assay for human cytokines. Data were analyzed using one-way ANOVA model with Tukey’s post hoc tests. Doxycycline treatment decreased NLRP3 formation in PC3 and A549 cells compared to untreated and LPS only treated cells (p < 0.05). Doxycycline also decreased proliferation and caused cell death through apoptosis, a response that differed to the LPS-Nigericin mediated pyroptosis. Our findings suggest that doxycycline inhibits LPS priming of NLRP3 and reduces tumor progression through early apoptosis in cancer.

Anti-cancer potential of some commonly used drugs

Cancer is a global concern leading to millions of deaths every year. A declining trend in new drug discovery and development is becoming one of the major issues among the pharmaceutical, biotechnology industries, and regulatory agencies. New drug development is proven to be a very lengthy and costly process. The launch of a new drug takes 8-12 years and huge investments. The success rate in oncology therapeutics is also low due to toxicities at the pre-clinical and clinical trial levels. Many oncological drugs get rejected at a very promising stage, showing adverse reactions on healthy cells. Thus, exploring new therapeutic benefits of the existing, shelved drugs for their anti-cancerous action could result in a therapeutic approach preventing the toxicities which occur during clinical trials. Drug repurposing has the potential to overcome the challenges faced via conventional way of drug discovery and is becoming an area of interest for researchers and scientists. However, very few in vivo studies are conducted to prove the anti-cancerous activity of the drugs. Insufficient in vivo animal studies and a lack of human clinical trials are the lacunae in the field of drug repurposing. This review focuses on an aspect of drug repurposing for cancer therapeutics. Various studies that show that drugs approved for clinical indications other than cancer have shown promising anti-cancer activities. Some of the commonly used drugs like Benzodiazepines (Diazepam, Midzolam), Antidepressants (Imipramine, Clomipramine, and Citalopram), Antiepileptic (Valporic acid, Phenytoin), Antidiabetics (metformin), etc. have been reported to show potential activity against the cancerous cells.

Identification of the targeted therapeutic potential of doxycycline for a subset of gastric cancer patients

The identification of new drugs for the targeted therapy of gastric cancer remains an important need. The RAS/RAF/MEK/ERK/ELK1 signaling cascade is activated in many cancers, including gastric cancer. To identify the targetable inhibitors of the ERK/MAPK pathway, we performed a repurposing screening of a panel of antimicrobial agents in gastric cancer cells using an ERK/MAPK-driven firefly luciferase reporter assay. Multiple antibiotics were identified to inhibit ERK-mediated transcriptional activity. Among them, doxycycline showed high inhibition of ERK/MAPK-regulated transcriptional activity and the levels of ERK proteins. Doxycycline was further identified to inhibit the proliferation and the colony- and spheroid-forming potential of gastric cancer cells. By in vitro signaling pathway and genome-wide expression profiling analyses, doxycycline was identified to inhibit signaling pathways and transcriptional activities regulated by ER, Myc, E2F1, Wnt, SMAD2/3/4, Notch, and OCT4. Doxycycline was also found to activate p53-, ATF6-, NRF1/2-, and MTF1-mediated transcription and inhibit the transcription of histones, proteasomal genes, fibroblast growth factor, and other oncogenic factors. These observations show the multitargeting and targeted therapeutic features of doxycycline for a subset of gastric tumors.

HAMPT, A Novel Quadruple Drug Combination Designed for Cancer Metastatic Chemoprevention: From Hypothesis to Proof-of-concept

BACKGROUND

Highly Active Metastasis Preventing Therapy (HAMPT) is a quardruple drug combination consisting of mifepristone, aspirin, lysine and doxycycline.

OBJECTIVE

Based on our previous study, here, we further proved that HAMPT could effectively and safely prevent colon cancer metastasis.

METHODS

It was specifically designed for synergistically controlling key cancer metastatic pathways. The dose of HAMPT was designed at lower than the pharmaceutically-recommended dose, and thus the sub-healthy cancer survivors may take HAMPT safely and for a long time for metastasis chemoprevention.

RESULTS

HAMPT within its effective concentration range (1-50 µg/mL) showed no cytotoxicity to colon cancer cells HT-29 and CT-26, but significantly inhibited adhesion and invasion of these colon cancer cell lines to human umbilical vascular endothelial cells (HUVECs), and to Matrigel. HAMPT exhibits a good adhesion inhibited ratio, suggesting that it functions primarily by inhibiting adhesion of the cancer cells to HUVECs, rather than killing the cancer cells. At low concentrations, HAMPT also inhibited cancer cell migration. Flow cytometry analysis revealed that HAMPT had no significant effect on cell cycle, but inhibited IL-1β-induced expression of both E-selectin of HUVECs and Sialyl-Lewis X of HT-29. The in vivo experiment showed that HAMPT suppressed metastasis of CT-26 cells to mouse lungs in a dose-dependent manner. In the mouse model, HAMPT showed advantages in preventing metastasis over other combinations.

CONCLUSION

The present study demonstrated that HAMPT is a novel quadruple drug combination that can safely and effectively prevent cancer metastasis.

Profilin-1 deficiency leads to SMAD3 upregulation and impaired 3D outgrowth of breast cancer cells

BACKGROUND

Adhesion-mediated activation of FAK/ERK signalling pathway, enabled by the formation of filopodial protrusions (FLP), has been shown to be an important event for triggering of dormancy-to-proliferation switch and metastatic outgrowth of breast cancer cells (BCC). We studied the role of actin-binding protein profilin1 (Pfn1) in these processes.

METHODS

Quantitative immunohistochemistry (IHC) of BC tissue microarray (TMA) and survival analyses of curated transcriptome datasets of BC patients were performed to examine Pfn1's association with certain clinicopathological features. FLP formation and single cell outgrowth of BCC were assessed using a 3D matrigel culture that accurately predicts dormant vs metastatic outgrowth phenotypes of BCC in certain microenvironment. Gene expression studies were performed to identify potential biological pathways that are perturbed under Pfn1-depleted condition.

RESULTS

Lower Pfn1 expression is correlated with lower nuclear grade of breast tumours and longer relapse-free survival of BC patients. Pfn1 depletion leads to defects in FLP and outgrowth of BCC but without impairing either FAK or ERK activation. Guided by transcriptome analyses, we further showed that Pfn1 depletion is associated with prominent SMAD3 upregulation. Although knockdown and overexpression experiments revealed that SMAD3 has an inhibitory effect on the outgrowth of breast cancer cells, SMAD3 knockdown alone was not sufficient to enhance the outgrowth potential of Pfn1-depleted BCC suggesting that other proliferation-regulatory pathways in conjunction with SMAD3 upregulation may underlie the outgrowth-deficient phenotype of BCC cells upon depletion of Pfn1.

CONCLUSION

Overall, these data suggest that Pfn1 may be a novel biomarker for BC recurrence and a possible target to reduce metastatic outgrowth of BCC.

Doxycycline directly targets PAR1 to suppress tumor progression

Doxycycline have been reported to exert anti-cancer activity and have been assessed as anti-cancer agents in clinical trials. However, the direct targets of doxycycline in cancer cells remain unclear. In this study, we used a chemical proteomics approach to identify the Protease-activated receptor 1 (PAR1) as a specific target of inhibition of doxycycline. Binding assays and single-molecule imaging assays were performed to confirm the inhibition of doxycycline to PAR1. The effect of doxycycline on multi-omics and cell functions were assessed based on a PAR1/thrombin model. Molecular docking and molecular dynamic simulations revealed that doxycycline interacts with key amino acids in PAR1. Mutation of PAR1 further confirmed the computation-based results. Moreover, doxycycline provides highly selective inhibition of PAR1 signaling in tumors in vitro and in vivo. Using pathological clinical samples co-stained for doxycycline and PAR1, it was found that doxycycline fluorescence intensity and PAR1 expression shown a clear positive correlation. Thus, doxycycline may be a useful targeted anti-cancer drug that should be further investigated in clinical trials.

Drug repurposing in cancer

Cancer is a major health issue worldwide, and the global burden of cancer is expected to increase in the coming years. Whereas the limited success with current therapies has driven huge investments into drug development, the average number of FDA approvals per year has declined since the 1990s. This unmet need for more effective anti-cancer drugs has sparked a growing interest for drug repurposing, i.e. using drugs already approved for other indications to treat cancer. As such, data both from pre-clinical experiments, clinical trials and observational studies have demonstrated anti-tumor efficacy for compounds within a wide range of drug classes other than cancer. Whereas some of them induce cancer cell death or suppress various aspects of cancer cell behavior in established tumors, others may prevent cancer development. Here, we provide an overview of promising candidates for drug repurposing in cancer, as well as studies describing the biological mechanisms underlying their anti-neoplastic effects.

Doxycycline protects human intestinal cells from hypoxia/reoxygenation injury: Implications from an in-vitro hypoxia model

Intestinal ischemia/reperfusion (I/R) injury is a grave clinical emergency and associated with high morbidity and mortality rates. Based on the complex underlying mechanisms, a multimodal pharmacological approach seems necessary to prevent intestinal I/R injury. The antibiotic drug doxycycline, which exhibits a wide range of pleiotropic therapeutic properties, might be a promising candidate for also reducing I/R injury in the intestine. To investigate possible protective effects of doxycycline on intestinal I/R injury, human intestinal CaCo-2 cells were exposed to doxycycline at clinically relevant concentrations. In order to mimic I/R injury, CaCo-2 were thereafter subjected to hypoxia/reoxygenation by using our recently described two-enzyme in-vitro hypoxia model. Investigations of cell morphology, cell damage, apoptosis and hydrogen peroxide formation were performed 24h after the hypoxic insult. Hypoxia/reoxygenation injury resulted in morphological signs of cell damage, elevated LDH concentrations in the respective culture media (P<0.001) and increased protein expression of proapoptotic caspase-3 (P<0.05) in the intestinal cultures. These events were associated with increased levels hydrogen peroxide (P<0.001). Preincubation of CaCo-2 cells with different concentrations of doxycycline (5µM, 10µM, 50µM) reduced the hypoxia induced signs of cell damage and LDH release (P<0.001 for all concentrations). The reduction of cellular damage was associated with a reduced expression of caspase-3 (5µM, P<0.01; 10µM, P<0.01; 50µM, P<0.05), while hydrogen peroxide levels remained unchanged. In summary, doxycycline protects human intestinal cells from hypoxia/reoxygenation injury in-vitro. Further animal and clinical studies are required to prove the protective potential of doxycycline on intestinal I/R injury under in-vivo conditions.

Release and cytotoxicity studies of magnetite/Ag/antibiotic nanoparticles: An interdependent relationship

Though the cytotoxic properties of magnetite nanoparticles (NPs) are rather well investigated and known to be dose dependent and rather low, surface functionalization can drastically change their properties. To determine whether the cytotoxicity of magnetite/Ag/antibiotic NPs may be associated, among other things, with iron, silver and antibiotic release, this study investigates the release profiles and cytotoxicity of magnetite/Ag/rifampicin and magnetite/Ag/doxycycline NPs compares it similar profiles from magnetite, magnetite/Ag NPs and antibiotics. It was established that the studied NPs released not only water-soluble substances, such as antibiotics, but also poorly-soluble ones, such as iron and silver. The deposition of silver on the magnetite surface promotes the release of iron by the formation of a galvanic couple. Antibiotic adsorbed on the magnetite/Ag surface plays a dual role in the galvanic corrosion processes: as a corrosion inhibitor for iron oxides and as a corrosion promoter for silver. Magnetite/Ag/rifampicin and magnetite/Ag/doxycycline. NPs were found to have greater cytotoxicity towards the HEK293T cell line than magnetite NPs. These results were attributed to the combined toxic action of the released iron, silver ions and antibiotics. Intensive and simultaneous release of the NP components caused cell stress and suppressed their growth.

Aspirin, lysine, mifepristone and doxycycline combined can effectively and safely prevent and treat cancer metastasis: prevent seeds from gemmating on soil

Recent scientific advances have increased our understanding of the cancer metastatic complexities and provided further impetus for new combination therapies to prevent cancer metastasis. Here, we demonstrated that a combination (HAMPT) of aspirin, lysine, mifepristone and doxycycline can effectively and safely prevent cancer metastasis. The pharmaceutically-formulated HAMPT inhibited adhesion of cancer cells to either endothelial cells or extracellular matrix via down-regulating cell adhesion molecules ICAM-1 and α₄-integrin. HAMPT inhibited the cloak effect by activated platelets on cancer cells, thereby interfering adhesion and invasion of cancer cells to the underlying stroma. At the effective concentration, HAMPT induced cancer cells into dormancy with minor inhibition on cell viability. Four-day pretreatment followed by 30-day oral administration of HAMPT (33.5-134 mg/kg) to the mice inoculated with cancer cells produced significant inhibition on cancer metastasis dose-dependently without marked side effects. Fifty-day rat toxicity study with HAMPT at doses (335-1340 mg/kg) 20-fold higher than its therapeutic dose produced no significant toxicity. Interestingly, the acute toxic death could not be reached at the maximum administrable dose (5 g/kg). This proof-of-concept study provides the first conceptual evidence that cancer metastasis can be controlled by using affordable old drugs to restrain circulating tumor cells from gemmating on the metastatic soil without the need for cytotoxicity.

Preclinical trial on the use of doxycycline for the treatment of adenocarcinoma of the duodenum

Adenocarcinoma of the duodenum comprises 50-70% of duodenal tumors. There is an increase in extracellular matrix metalloproteinases in this disease and it has been suggested that they play an important role in the development and pathology. Therefore, new therapeutic recommendations based on inhibitors of these enzymes, such as doxycycline, are under investigation. The cytotoxic effect of doxycycline was evaluated in the HuTu-80 duodenal adenocarcinoma cell line and its antitumor effect was determined in an immunodeficient murine model. A 10-µM (4.4 µg/ml) concentration of doxycycline was capable of causing apoptosis in 90% of the culture cells. Doxycycline was also responsible for a decrease in tumor growth and an increase in the survival of the mice with HuTu-80-cell tumors. These results suggest that doxycycline is a potential cytotoxic and antitumor agent effective in the treatment of adenocarcinoma of the duodenum.

Pharmacodynamic considerations in the use of matrix metalloproteinase inhibitors in cancer treatment

INTRODUCTION

Matrix metalloproteinases (MMPs) are classified in the family of zinc-dependent endopeptidases, which can degrade various components of an extracellular matrix and a basement membrane. Studies have demonstrated that MMPs relate to the development of malignant tumors and induce angiogenesis, resulting in the invasion and metastasis of tumor cells. MMPs are highly expressed in malignant tumors and are related to cancer patients' malignant phenotype and poor prognosis. Therefore, blocking the expression or activity of MMPs may be a promising strategy for cancer treatment.

AREAS COVERED

This study aimed to explain the MMP structure, regulatory mechanism, and carcinogenic effect; investigate the matrix metalloproteinase-inhibitors (MMPIs) that are currently used in clinical trials for cancer treatment; and summarize the trial results.

EXPERT OPINION

Currently, the results of clinical trials that have used MMPIs as anticancer agents are unsatisfactory. However, MMPs remain an attractive target for cancer treatment. For example, development of the specific peptide or antibodies in targeting the hemopexin domain of MMP-2 may be a new therapeutic direction. The design and development of MMPIs that have selectivity will be the primary focus in future studies.

Toxicological Implications and Inflammatory Response in Human Lymphocytes Challenged with Oxytetracycline

Antibiotics are widely used in zoo technical and veterinary practices as feed supplementation to ensure wellness of farmed animals and livestock. Several evidences have been suggesting both the toxic role for tetracyclines, particularly for oxytetracycline (OTC). This potential toxicity appears of great relevance for human nutrition and for domestic animals. This study aimed to extend the evaluation of such toxicity. The biologic impact of the drug was assessed by evaluating the proinflammatory effect of OTC and their bone residues on cytokine secretion by in vitro human peripheral blood lymphocytes. Our results showed that both OTC and OTC‐bone residues significantly induced the T lymphocyte and non‐T cell secretion of interferon (IFN)‐γ, as cytokine involved in inflammatory responses in humans as well as in animals. These results may suggest a possible implication for new potential human and animal health risks depending on the entry of tetracyclines in the food‐processing chain.

Low concentrations of doxycycline attenuates FasL-induced apoptosis in HeLa cells

Background

Doxycycline (DC) has been shown to possess non-antibiotic properties including Fas/Fas Ligand (FasL)-mediated apoptosis against several tumor types in the concentration range of 10–40 µg/mL. However, the effect of DC in apoptotic signaling at much low concentrations was not studied.

Methods

The present study investigated the attenuation effect of low dose of DC on FasL-induced apoptosis in HeLa cell by the methods of MTT assay, fluorescence microscopy, DNA fragmentation, flow cytometry analysis, and western blotting.

Results and conclusion

In the present findings we showed that low concentration of DC (<2.0 µg/mL) exhibited protective effects against FasL-induced apoptosis in HeLa cells. FasL treatment to HeLa cells resulted in a concentration-dependent induction of cell death, and treatment with low concentrations of DC (0.1–2 µg/mL) significantly (p < 0.001) attenuated the FasL-induced cell death as measured by 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Further, the FasL-induced apoptotic features in HeLa cells, such as morphological changes, DNA fragmentation and cell cycle arrest was also inhibited by DC (0.5 µg/mL). Tetracycline and minocycline also showed similar anti-apoptotic effects but were not significant when compared to DC, tested at same concentrations. Further, DC (0.01–16 µg/mL) did not influence the hydrogen peroxide- or cisplatin-induced intrinsic apoptotic pathway in HeLa cells. Protein analysis using Western blotting confirmed that FasL-induced cleavage/activation of caspase-8 and caspase-3, were inhibited by DC treatment at low concentration (0.5 µg/mL). Considering the overall data, we report for the first time that DC exhibited anti-apoptotic effects at low concentrations in HeLa cells by inhibition of caspase activation via FasL-induced extrinsic pathway.

Electronic supplementary material

The online version of this article (doi:10.1186/s40659-015-0025-8) contains supplementary material, which is available to authorized users.

Doxycycline inhibits leukemic cell migration via inhibition of matrix metalloproteinases and phosphorylation of focal adhesion kinase

Doxycycline, a tetracycline-based antibiotic, has been reported to attenuate melanoma cell migration through inhibiting the focal adhesion kinase (FAK) signaling pathway. However, it remains to be elucidated whether doxycycline exerts this effect on leukemia cell migration. The present study aimed to examine the role of doxycycline in leukemia cell migration. The invasion capacities of the human leukemia cell lines KG1a (acute myelogenous leukemia) and K562 (chronic myelogenous leukemia) were evaluated using Matrigel® matrix‑coated Transwell® chamber assays; leukemic cell lines treated with doxycycline (1 µg/ml) or anti‑β1‑integrin antibodies were added to the upper chamber, while untreated cells were included as controls. Reverse transcription quantitative polymerase chain reaction was performed in order to further understand the influence of doxycycline treatment on the expression of FAK and gelatinases in the KG1a and K562 leukemic cell lines. In addition, FAK protein expression and phosphorylation were determined using western blot analysis in order to investigate the mechanism by which doxycycline inhibited leukemic cell migration. The results revealed that doxycycline treatment significantly attenuated the migration of KG1a and K562 cells, which was demonstrated to be associated with inhibition of the expression and phosphorylation of FAK. In addition, doxycycline treatment inhibited matrix metalloproteinase (MMP)‑2 and MMP‑9 expression. Furthermore, incubation with blocking anti‑β1‑integrin antibodies had an analogous inhibitory effect on leukemic cell migration to that of doxycycline. In conclusion, the results of the present study suggested that doxycycline attenuated leukemic cell migration through inhibiting the FAK signaling pathway. Therefore, doxycycline may have potential for use as a novel strategy for the treatment of leukemia.

The genetics of age-related macular degeneration (AMD)--Novel targets for designing treatment options?

Age-related macular degeneration (AMD) is a progressive disease of the central retina and the main cause of legal blindness in industrialized countries. Risk to develop the disease is conferred by both individual as well as genetic factors with the latter being increasingly deciphered over the last decade. Therapeutically, striking advances have been made for the treatment of the neovascular form of late stage AMD while for the late stage atrophic form of the disease, which accounts for almost half of the visually impaired, there is currently no effective therapy on the market. This review highlights our current knowledge on the genetic architecture of early and late stage AMD and explores its potential for the discovery of novel, target-guided treatment options. We reflect on current clinical and experimental therapies for all forms of AMD and specifically note a persisting lack of efficacy for treatment in atrophic AMD. We further explore the current insight in AMD-associated genes and pathways and critically question whether this knowledge is suited to design novel treatment options. Specifically, we point out that known genetic factors associated with AMD govern the risk to develop disease and thus may not play a role in its severity or progression. Treatments based on such knowledge appear appropriate rather for prevention than treatment of manifest disease. As a consequence, future research in AMD needs to be greatly focused on approaches relevant to the patients and their medical needs.

Experimental design for stable genetic manipulation in mammalian cell lines: lentivirus and alternatives

The use of third-generation lentiviral vectors is now commonplace in most areas of basic biology. These systems provide a fast, efficient means for modulating gene expression, but experimental design needs to be carefully considered to minimize potential artefacts arising from off-target effects and other confounding factors. This review offers a starting point for those new to lentiviral-based vector systems, addressing the main issues involved with the use of lentiviral systems in vitro and outlines considerations which should be taken into account during experimental design. Factors such as selecting an appropriate system and controls, and practical titration of viral transduction are important considerations for experimental design. We also briefly describe some of the more recent advances in genome editing technology. TALENs and CRISPRs offer an alternative to lentivirus, providing endogenous gene editing with reduced off-target effects often at the expense of efficiency.

Tetracycline and Glutathione Inhibit Matrix Metalloproteinase Activity: An In Vitro Study Using Culture Supernatants of L929 and Dalton Lymphoma Cell Lines

Tetracycline and glutathione inhibited the protease activities of matrix metalloproteinase-2 and matrix metalloproteinase-9 expressed by mouse fibrosarcoma cells (L929) and Dalton lymphoma cells, respectively. The inhibitory activity of the tetracycline may be due to its ability to chelate metal ions such as calcium and zinc. Gelatin-zymography technique was used to demonstrate the inhibitory activity of both tetracycline and glutathione. The intensity of the bands corresponding to metalloproteinase activity in zymography gel was reduced in the presence of 50–100 μg/mL of tetracycline. The presence of 10–100 μg/mL of tetracycline in the medium increased the adherence of L929 cancer cells. These results clearly indicate the antimetastatic property of tetracycline. Reduced glutathione, a compound which is produced endogenously by the cells to maintain the redox status, was shown to inhibit the matrix metalloproteinase activity (in vitro). Therefore, it is assumed that decreased glutathione levels in synovial fluids or plasma might increase the activity of MMP. Reduced glutathione at 100 μg/mL inhibited the metalloproteinase activity in gelatin-zymographic gel. As both tetracycline and glutathione exhibited an inhibitory effect on matrix metalloproteinase activity, it was of great interest to check their clinical effects on various MMP associated pathological conditions such as cancer metastasis and arthritis. Here we report that tetracycline and reduced glutathione inhibited the activity of MMP2 completely and activity of MMP9 partly.

Striking growth-inhibitory effects of minocycline on human prostate cancer cell lines

OBJECTIVE

To elucidate a hypothetical link between retinoic acid (RA) signaling and minocycline for targeting prostate carcinoma (PCA). RA signaling has been implicated in growth-inhibition of malignant PCA, and intracellular RA homeostasis has been investigated as a potential therapeutic target. Minocycline is a tetracycline antibiotic with pleiotropic actions in many tissues and reaches comparably high levels in human prostate tissue. Interestingly, minocycline exhibits the rare side effect of a pseudotumor cerebri, which is otherwise known to occur from vitamin A intoxication or in retinoid therapy. Therefore, we hypothesized minocycline to putatively interact with intracellular RA homeostasis in PCA.

METHODS

Using LN-CAP, DU-145, and PC-3 cell lines, effects of minocycline on microsomal RA metabolism and on cell growth were assessed in vitro.

RESULTS

Minocycline was identified to potently inhibit cell growth, at concentrations within the range of tissue levels readily reached under standard therapeutic conditions. In vitro inhibition experiments revealed inhibition of RA breakdown, yet only at comparably high concentrations of minocycline. Using all trans-RA, RA metabolism inhibitor liarozole, and different retinoid receptor antagonists, the putative RA-dependent effects of minocycline were further evaluated and confirmed to be independent of RA signaling.

CONCLUSION

Our findings add to the growing body of evidence for the many pleiotropic actions of minocycline. In view of the striking effects of minocycline on cell growth in PCA cell lines in vitro and its relatively safe side effect profile, the use of minocycline for targeting PCA should be timely clinically evaluated.

Doxycycline alters metabolism and proliferation of human cell lines

The tetracycline antibiotics are widely used in biomedical research as mediators of inducible gene expression systems. Despite many known effects of tetracyclines on mammalian cells–including inhibition of the mitochondrial ribosome–there have been few reports on potential off-target effects at concentrations commonly used in inducible systems. Here, we report that in human cell lines, commonly used concentrations of doxycycline change gene expression patterns and concomitantly shift metabolism towards a more glycolytic phenotype, evidenced by increased lactate secretion and reduced oxygen consumption. We also show that these concentrations are sufficient to slow proliferation. These findings suggest that researchers using doxycycline in inducible expression systems should design appropriate controls to account for potential confounding effects of the drug on cellular metabolism.

OTX2 represses myogenic and neuronal differentiation in medulloblastoma cells

The brain development transcription factor OTX2 is overexpressed and/or genomically amplified in most medulloblastomas, but the mechanistic basis for its contributions in this setting are not understood. In this study, we identified OTX2 as a transcriptional repressor and a gatekeeper of myogenic and neuronal differentiation in medulloblastoma cells. OTX2 binds to the MyoD1 core enhancer through its homeobox domain, and the remarkable repressor activity exhibited by the homeobox domain renders OTX2 transcriptionally repressive. RNA interference-mediated attenuation of OTX2 expression triggered myogenic and neuronal differentiation in vitro and prolonged the survival in an orthotopic medulloblastoma mouse model. Conversely, inducing myogenic conversion of medulloblastoma cells led to the loss of OTX2 expression. In medullomyoblastoma, a medulloblastoma subtype containing muscle elements, myogenic cells share cytogenetic signatures with the primitive tumor cells and OTX2 expression was lost in the differentiated myogenic cells. Thus, OTX2 functions via its homeobox domain as a suppressor of differentiation, and the loss of OTX2 expression is linked to the myogenesis in medullomyoblastoma. Together, our findings illustrate the origin of muscle cells in medullomyoblastomas and the oncogenic mechanism of OTX2 as a repressor of diverse differentiating potential.

Genotoxic and cytotoxic effects of doxycycline in cultured human peripheral blood lymphocytes

Doxycycline (DOX) is a broad-spectrum tetracycline antibiotic used in the treatment of many infections. In this study, the genotoxic and cytotoxic effects of DOX in cultured human peripheral blood lymphocytes were investigated by measuring chromosome aberrations (CAs), cytokinesis-block micronucleus (CBMN) assay, mitotic index (MI), and nuclear division index (NDI). Cultures were treated with DOX at three concentrations (2, 4, and 6 µg/mL) for 48 hours. Mitomycin C (MMC) was used as a positive control. All the tested concentrations of DOX for MI and the higher concentrations (4 and 6 µg/mL) for NDI significantly decreased mitotic activity. However, there are no significant differences between negative control and all the tested concentrations of DOX for CA and MN frequencies. In conclusion, our results indicate that DOX has a cytotoxic effect, but not a genotoxic effect, on human peripheral blood lymphocyte cultures. Further detailed studies, especially about the cell-cycle kinetics of DOX, are required to elucidate the decreases in dividing cells and make a possible risk assessment on cells of patients receiving therapy with this drug. Further, if the specific cytostatic and cytotoxic potential of DOX to different types of cancer cells is investigated in detail, it may also have been used as an antitumoral drug.

Lowering the apoptotic threshold in colorectal cancer cells by targeting mitochondria

Background

Colorectal cancer is the third most-common cancer and the second most-common cause of cancer related death in UK. Although chemotherapy plays significant role in the treatment of colorectal cancer, morbidity and mortality due to drug resistance and cancer metastasis are yet to be eliminated. Recently, doxycycline has been reported to have cytotoxic and anti-proliferating properties in various cancer cells. In this study, whether doxycycline was apoptosis threshold lowering agent in colorectal cancer cells by targeting mitochondria was answered.

Results

This study showed dose-dependent cytotoxic effects of cisplatin, oxaliplatin and doxycycline in HT29 colorectal cancer cells. Doxycycline showed inhibition of cytochrome-c-oxidase activity in these cells over a time-period. The pre-treatment of doxycycline reported statistically significant increased cytotoxicity of cisplatin and oxaliplatin compared to cisplatin and oxaliplatin alone. The caspase studies revealed significantly less expression and activity of caspase 3 in HT29 cells pre-treated with doxycycline compared to the cells treated with cisplatin and oxaliplatin alone.

Conclusions

It was concluded that doxycycline lowered the apoptotic threshold in HT 29 cells by targeting mitochondria. This also raised possible caspase-independent mechanisms of apoptosis in HT29 cells when pre-treated with doxycycline however this needs further research work.

Anti-invasion and anti-tumor growth effect of doxycycline treatment for human oral squamous-cell carcinoma--in vitro and in vivo studies

Regional lymph node and distant organ metastasis of oral squamous-cell carcinoma (OSCC) has been associated with increased production of matrix metalloproteases (MMPs), and scientific data showed that doxycycline (Dox) could down-regulate the expression of MMPs. The objective of this study was to evaluate the effect of Dox on the expression of MMPs in vitro using the SCC-15 cell line and in vivo SCC-15 xenografted nude mice. SCC-15 cells maintained under distinct culture conditions expressed high levels of pro-MMP-2 and pro-MMP-9; however, as determined by zymography and Western blot analysis, Dox significantly reduced the production of pro-MMP-2 and pro-MMP-9 after 24h of treatment in a dose-dependent manner (2.5-40 microg/ml). Dox (10 microg/ml) decreased the expression of MMP-9 mRNA but did not alter the level of MMP-2 mRNA after 24h of treatment. In addition, this drug significantly inhibited the invasive and migration activities of SCC-15 cells in vitro (>75% inhibition at 10 microg/ml). On the other hand, daily administration of Dox (3mg/mice) restrained tumor growth in SCC-15 xenografted nude mice, with an inhibition rate of 85.6%. Compared with the control group (treated with normal saline), MMP-9 mRNA levels in the fresh tumor tissue decreased upon Dox treatment (P<0.01) while MMP-2 mRNA levels were unchanged. In conclusion, reduced expression of MMP-9 at the transcriptional level and MMP-2 at the post-transcriptional level caused by Dox was found to be associated with decreased invasion of oral SCC in vitro. Moreover, Dox exerted a significant suppressive effect on tumor growth in an in vivo nude mice model. Taken together, these results, to our knowledge, may first imply that Doxycycline has an adjuvant therapeutic effect on OSCC that is associated with inhibition of MMPs expression.

Doxycycline enhances the Ras-MAPK signaling and proliferation of mouse thymic epithelial cells

Depletion of T-cell-dependent immunity is a major consideration for patients suffering from infections of human immunodeficiency virus (HIV), those undergoing organ transplantation, and those receiving anti-cancer chemotherapy and/or radiotherapy. In general, T-cell regeneration occurs in the thymus through thymopoiesis. We have found that doxycycline (Dox), a tetracycline derivative, enhances the proliferation of mouse thymic epithelial cells, which are unique in their capacity to support positive selection and are essential throughout the development of thymocytes. Cell cycle analysis indicates that the increased cell proliferation is due to a shortened G(0)/G(1) phase. To reveal the underlying mechanisms, we examined the expression of an array of molecules that regulate the cell cycle. The results show that in mouse thymic medullary-type epithelial cell line 1 (MTEC1) Dox leads to elevated levels of H-Ras, phosphorylated extracellular signal-regulated kinase 1/2 (p-ERK1/2), cyclin E, cyclin dependent kinase 4/2 (CDK4/CDK2), E2F3, and c-myc. These data, and the observation that the proliferation-enhancing effect is largely abolished following treatment with an ERK inhibitor support an active role of the Ras-ERK/mitogen-activated protein kinase (MAPK) signaling pathway. In conclusion, the present study reveals a new activity of an old family of antibiotics. The in vivo effect of Dox on immune reconstitution warrants further exploration.

Characterization of the RSL1-dependent conditional expression system in LNCaP prostate cancer cells and development of a single vector format

BACKGROUND

Conditional expression systems are useful tools for the study of gene function but the use of these systems in prostate cancer cells is limited by the undesired biological effects of the inducing ligands. The RheoSwitch system employs RheoSwitch Ligand 1 (RSL1), a non-steroidal analog of the insect hormone ecdysone, to activate a modified nuclear receptor heterodimer that controls target gene expression via GAL4 response elements. This system has not been tested in prostate cancer cells.

METHODS

We established LNCaP human prostate cancer cell lines that constitutively express RheoSwitch transcription factors to quantify RSL1-dependent expression and assess the effects of RSL1 on cell proliferation and endogenous gene expression. Potential RSL1-responsive genes were identified using Affymetrix microarrays and validated by Northern blot hybridization. A single-vector format was developed to establish cell lines that conditionally produce a recombinant protein.

RESULTS

Stable cell lines displayed tight and potent (over several orders of magnitude) RSL1-dependent regulation of a transiently transfected luciferase reporter gene. RSL1 did not affect basal or androgen-stimulated cell proliferation and exerted minimal effects on the expression of endogenous genes. Cell lines established using the single-vector system also displayed strictly RSL1-dependent production of the recombinant protein encoded by the stably integrated RSL1-responsive expression cassette.

CONCLUSIONS

The RheoSwitch system is well suited for conditional gene expression in prostate cancer cells. The single-vector format should facilitate the production of stable cell lines. This system should be useful for the study of proteins involved in prostate cancer in both cell and animal models of the disease.

Doxycycline induces caspase-dependent apoptosis in human pancreatic cancer cells

Doxycycline (DC) belongs to the tetracycline family of antibiotics and has been used clinically for over 5 decades. Despite advances in understanding the molecular pathogenesis of pancreatic cancer, no chemotherapy course has shown significant effectiveness. Hence new treatments are needed. In this study we report the pro-apoptotic effects of DC in 2 pancreatic adenocarcinoma cell lines, T3M4 and GER. Cell proliferation was measured using the SRB protein dye. Induction of apoptosis was detected using ELISA. Caspase activation was detected using either immunoblotting or a colorimetric assay based on cleavage of caspase-associated substrates. Expression of proteins and post-translational modifications were determined using immunoblotting. Treatment of pancreatic cancer cells with DC reduces their proliferation. This reduction is, at least partly, due to increased caspase-dependent apoptosis involving activation of caspase3, caspase7, caspase8, caspase9, caspase10 and increased levels of FADD. Inhibition of caspase8 or caspase10 but not caspase9 significantly decreases DC-induced apoptosis in both cell lines. Furthermore treatment of pancreatic cancer cells with DC increases protein levels of Bax and phosphorylation of members of the p38MAPK pathway such as p38MAPK, MKK3/6 and MAPKAPK2. These results provide an insight into mechanisms behind the pro-apoptotic effects of DC in pancreatic cancer cells.

Doxycycline alters vascular smooth muscle cell adhesion, migration, and reorganization of fibrillar collagen matrices

Remodeling of injured blood vessels is dependent on smooth muscle cells and matrix metalloproteinase activity. Doxycycline is a broad spectrum matrix metalloproteinase inhibitor that is under investigation for the treatment of acute coronary syndromes and aneurysms. In the present study, we examine the mechanisms by which doxycycline inhibits smooth muscle cell responses using a series of in vitro assays that mimic critical steps in pathological vascular remodeling. Doxycycline treatment dramatically increased smooth muscle cell adhesion to the substrate, as evidenced by interference reflection microscopy and immunostaining for paxillin and phosphotyrosine. Cell aggregation was also potentiated after treatment with doxycycline. Treatment with 104 mumol/L doxycycline reduced thymidine uptake by 58% compared with untreated cells (P < 0.05) and inhibited closure of a scrape wound made in a smooth muscle cell monolayer by 20% (P < 0.05). Contraction of a three-dimensional collagen gel was used as an in vitro model for constrictive vessel remodeling, demonstrating that treatment with 416 mumol/L doxycycline for 12 hours inhibited collagen gel remodeling by 37% relative to control (P < 0.05). In conclusion, we have shown that doxycycline treatment leads to dramatically increased smooth muscle cell adhesion, which in turn might limit responses in pathological vascular remodeling.

Phase II study of interferon-alpha and doxycycline for advanced renal cell carcinoma

OBJECTIVE

To assess the efficacy and toxicity of the combination of interferon-alpha and doxycycline in patients with metastatic renal cell carcinoma and to assess the effect of this treatment on serum vascular endothelial growth factor (VEGF) levels.

PATIENTS AND METHODS

Seventeen patients with Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1 and life expectancy greater than 4 months with radiologically evident advanced renal cell carcinoma were enrolled. Eight patients had prior nephrectomy and 10 patients were treated within 4 months of their diagnosis. Treatment consisted of interferon-alpha up to 9 million units subcutaneously three times per week and doxycycline 300 mg orally twice per day for weeks one and three of each four-week cycle. Toxicity was evaluated on a biweekly basis and response on a bimonthly basis. VEGF plasma levels were assessed monthly as a measure of potential antiangiogenic effect.

RESULTS

No objective responses were seen. The mean duration of study was 2.6 cycles (range: 0.8-6.0 cycles). Three patients (17%) tolerated therapy and displayed stable disease for greater than four months. Five patients withdrew from study before the first response evaluation. Ten patients experienced grade 2 gastrointestinal toxicity requiring dose reduction of doxycycline. Eight patients experienced grade 2 fatigue requiring dose reduction of interferon. VEGF plasma levels were initially suppressed in patients who demonstrated progressive disease but not in patients with stable disease.

CONCLUSION

This regimen of doxycycline and interferon-alpha was not efficacious as treatment for renal cell carcinoma. Plasma VEGF levels were significantly decreased during the first two cycles of treatment, but this does not correlate with clinical outcome.

Acne in adolescence and cause-specific mortality: lower coronary heart disease but higher prostate cancer mortality: the Glasgow Alumni Cohort Study

Androgen level or androgen activity is implicated in several health outcomes, but its independent role remains controversial. This study investigated the association between history of acne in young adulthood, a marker of hormone activity, and cause-specific mortality in the Glasgow Alumni Cohort Study. Male students who attended Glasgow University between 1948 and 1968 and participated in voluntary health checks reported history of acne (n = 11,232). Vital status has been traced, and risk factors in adulthood are known for about 50% of the participants. Those with a history of acne were more often nonsmokers while university students and tended to be from a lower socioeconomic position. The two groups did not differ in other adolescent (height, body mass index, blood pressure, and number of siblings) or in most adult risk factors. Students who reported a history of acne had a lower risk of all-cause (hazard ratio = 0.89, 95% confidence interval (CI): 0.76, 1.04) and coronary heart disease (hazard ratio = 0.67, 95% CI: 0.48, 0.94) mortality but had some evidence of a higher risk of prostate cancer mortality (hazard ratio = 1.67, 95% CI: 0.79, 3.55). This study shows that androgen activity during adolescence may protect against coronary heart disease but confer a higher risk of prostate cancer mortality.

Inhibition by doxycycline of angiogenesis in the chicken chorioallantoic membrane (CAM)

Doxycycline, a tetracycline derivative, has many properties in addition to its antibiotic activity, including inhibition of matrix metalloproteinases (MMPs) and the ability to chelate divalent cations including Ca(2+). It has been shown to inhibit endothelial cell growth in vitro, and reduce the development of experimental tumours, especially bone metastasis in a model of breast cancer. We examined the effects of doxycycline on angiogenesis in the chicken chorioallantoic membrane (CAM) model, and showed that doxycycline will cause loss of the chorionic plexus in CAMs when applied at day 8 of incubation, and the duration of this inhibition was dose-dependent. Repeated doses prolonged the inhibition, but following removal of the doxycycline there was rapid recovery of the chorionic plexus. The effects of doxycycline are in part mimicked by the MMP inhibitor 1,10-phenanthroline, and more closely by the Ca(2+)-chelating agent EGTA. Doxycycline was equally effective in causing loss of the chorionic plexus by day 11 in CAMs, a time at which the blood vessels are established. Doxycycline has important potential as an antiangiogenic treatment. It is capable of inhibiting angiogenesis in an in vivo model, including the removal of comparatively mature endothelial cells. The response is sensitive to the dosing regimen and the effect is rapidly reversible.

Chemically modified tetracyclines as inhibitors of matrix metalloproteinases

Matrix metalloproteinases belong to a diverse group of enzymes that are not only involved in restructuring the extracellular matrix, but also play a major role in various pathophysiological conditions by virtue of their complicated expression, activation, and regulation processes. They have been widely implicated to function as major contenders in cancer progression, frequently due to their role in invasion, proliferation and metastasis. MMP inhibitors have been specifically designed to target these altered activities of MMPs, mostly by means of inhibiting their function and by diminishing their increased expression in various disease states, particularly cancer. Tetracyclines and chemically modified tetracyclines (CMTs) have been rationally designed to inhibit the activity of MMPs and thus decrease the potential risk of spread of tumor cells to distant sites by invasion and metastasis. Pre-clinical and early clinical data for one of these CMTs, COL-3 (formerly CMT-3) indicate considerable potential for this group of anticancer agents. Further testing and rational modifications of these CMT analogues might lead to new anticancer agents.

Effects of cyclin-dependent kinase-5 activity on apoptosis and tau phosphorylation in immortalized mouse brain cortical cells

Cyclin-dependent kinase-5 (CDK5), a unique CDK family member, is active primarily in the central nervous system (CNS). Previous studies suggest that CDK5 is proapoptotic and contributes to tau hyperphosphorylation and neurodegeneration in Alzheimer's disease. The objective of this study was to examine CDK5 effects on apoptotic progression and tau phosphorylation. Immortalized embryonic mouse brain cortical cells were used to establish a stable cell line that overexpressed wild-type human tau. In these studies, thapsigargin, which induces endoplasmic reticulum stress and can cause accumulation of misfolded proteins, was used to induce apoptosis. Caspase-3 activity and poly-(ADP-ribose)-polymerase (PARP) cleavage, as measures of apoptosis, were significantly increased 24 and 48 hr after thapsigargin treatment, and these events were unaffected by tau expression. Although transient coexpression of CDK5 and its activator, p25, increased CDK5 activity greater than tenfold, increases in caspase-3 activity in response to thapsigargin treatment were unaffected by the presence of CDK5/p25. Tau phosphorylation at the PHF-1 epitope, but not the Tau-1 epitope, was increased significantly in CDK5/p25-transfected cells compared to cells transfected with dominant negative CDK5 (DNCDK5). The PHF-1 epitope remained phosphorylated until 48 hr after thapsigargin treatment in the CDK5/p25-transfected cells. Over the course of apoptosis in this model, phosphorylation of the Tau-1 epitope was unaffected in cells transfected with DNCDK5, vector, or CDK5/p25. In summary, these results demonstrate that CDK5 does not have a significant impact on tau phosphorylation and thapsigargin-induced apoptosis in this neuronal cell model.

Stabilization of p53 is a novel mechanism for proapoptotic function of NF-kappaB

Both pro- and antiapoptotic activities of NF-kappaB transcription factor have been observed; however, less is known about the mechanism by which NF-kappaB induces apoptosis. To elucidate how NF-kappaB regulates proapoptotic signaling, we performed functional analyses using wild-type, ikk1(-/-), ikk2(-/-), rela(-/-) murine fibroblasts, MDAPanc-28/Puro, MDAPanc-28/IkappaBalphaM, and HCT116/p53(+/+) and HCT116/p53(-/-) cells with investigational anticancer agent doxycycline as a superoxide inducer for generating apoptotic stimulus. In this report, we show that doxycycline increased superoxide generation and subsequently activated NF-kappaB, which in turn up-regulated p53 expression and increased the stability and DNA binding activity of p53. Consequently, NF-kappaB-dependent p53 activity induced the expression of p53-regulated genes PUMA and p21(waf1) as well as apoptosis. Importantly, lack of RelA, IKK, and p53 as well as expression of a dominant negative IkappaBalpha (IkappaBalphaM) inhibited NF-kappaB-dependent p53 activation and apoptosis. The doxycycline-induced NF-kappaB activation was not inhibited in HCT116/p53(-/-) cells. Our results demonstrate that NF-kappaB plays an essential role in activation of wild-type p53 tumor suppressor to initiate proapoptotic signaling in response to overgeneration of superoxide. Thus, these findings reveal a mechanism of NF-kappaB-regulated proapoptotic signaling.

Effect of combined cyclooxygenase-2 and matrix metalloproteinase inhibition on human sarcoma xenografts

PURPOSE

Sarcomas express cyclooxygenase (COX)-2, an inducible enzyme with known tumor-promoting activity. COX-2 inhibition is efficacious against many cancer types but has not been tested for human sarcomas. Matrix metalloproteinase (MMP) inhibitors also possess antiproliferative activity. Because MMP inhibitor therapy induces COX-2 expression, the authors hypothesized that the combination of COX-2 and MMP inhibitors results in a synergistic antitumor effect.

METHODS

Human osteosarcoma or rhabdomyosarcoma cells were injected into athymic mice. Tumor development and growth were measured following treatment with a COX-2 inhibitor (celecoxib), an MMP inhibitor (doxycycline), or both. The tumors were analyzed for necrosis, apoptosis, cyclooxygenase activity (PGE2 production), and MMP-2 levels.

RESULTS

When treatment was started prior to tumor cell implantation, doxycycline inhibited osteosarcoma tumor growth alone and in combination with celecoxib (30% and 33% reduction, respectively). An effect on osteosarcoma tumor implantation rates was noted in mice receiving doxycycline alone and in combination with celecoxib (12.5% and 6.25% reduction, respectively). Established osteosarcoma and rhabdomyosarcoma tumors were inhibited only by combination therapy (36% and 55%, respectively). A higher proportion of osteosarcoma tumors in the combination therapy group had more than 50% necrosis (3/7) when compared with control tumors (0/8). Antitumor effects did not correlate with PGE2 levels, suggesting the observed interaction with doxycycline was due to previously described non-enzymatic effects of celecoxib.

CONCLUSIONS

The authors' preclinical data suggest that the combination of inexpensive, nontoxic, oral COX-2 and MMP inhibitors may be useful for the treatment of some types of solid tumors.

Doxycycline induces apoptosis by way of caspase-3 activation with inhibition of matrix metalloproteinase in human T-lymphoblastic leukemia CCRF-CEM cells

Evidence for nonantibiotic activity displayed by tetracycline has been extensively reported in the field of antiinflammation. Here, we report a growth-inhibitory effect of doxycycline on CCRF-CEM, a T-lymphoblastic human leukemic cell line. Cells were incubated with doxycycline at concentrations ranging from zero to 50 micromol/L. We examined the hypothesis that induction of apoptosis is one of the mechanisms by which doxycycline inhibits CCRF-CEM proliferation. Caspase-3 activity of cells grown in the presence of 10 micromol/L and 50 micromol/L doxycycline increased dose-dependently after 24 hours in culture. The demonstration that doxycycline induces APO 2.7 expression in CCRF-CEM cells in vitro also supports its capacity for induction of apoptosis. The level of matrix metalloproteinase-2 was significantly lower in the medium cultured with 50 micromol/L doxycycline than the control. These phenomena suggest that this well-tolerated oral agent has the potential to be of value in antileukemic therapy.

Development of matrix metalloproteinase inhibitors in cancer therapy

The matrix metalloproteinases represent an attractive target for cancer treatment, and a number of matrix metalloproteinase inhibitors are undergoing clinical trials. The results of these studies will establish whether any of these compounds are therapeutically useful. Independent of the conclusions from the first generation of studies, the field of matrix metalloproteinase inhibitors remains attractive for creative and innovative research. In the future, the development of novel, less toxic, and more effective matrix metalloproteinase inhibitors, and the combination of conventional agents with these novel anticancer agents will constitute the main focus of research efforts.

Recent advances in inducible expression in transgenic mice

In order to accurately analyze gene function in transgenic mice, as well as to generate credible murine models of human diseases, the ability to regulate temporal- and spatial-specific expression of target genes is absolutely critical. Pioneering work in inducible transgenics, begun in the 1980s and continuing to the present, has led to the development of a variety of different inducible systems dedicated to this goal, the shared basis of which is the accurate conditional expression of a given transgene. Recent advances in inducible transgene expression in mice are discussed.