Current limitations of murine models in oncology for ascorbate research

High-dose intravenous vitamin C, a promising multi-targeting agent in the treatment of cancer

Mounting evidence indicates that vitamin C has the potential to be a potent anti-cancer agent when administered intravenously and in high doses (high-dose IVC). Early phase clinical trials have confirmed safety and indicated efficacy of IVC in eradicating tumour cells of various cancer types. In recent years, the multi-targeting effects of vitamin C were unravelled, demonstrating a role as cancer-specific, pro-oxidative cytotoxic agent, anti-cancer epigenetic regulator and immune modulator, reversing epithelial-to-mesenchymal transition, inhibiting hypoxia and oncogenic kinase signalling and boosting immune response. Moreover, high-dose IVC is powerful as an adjuvant treatment for cancer, acting synergistically with many standard (chemo-) therapies, as well as a method for mitigating the toxic side-effects of chemotherapy. Despite the rationale and ample evidence, strong clinical data and phase III studies are lacking. Therefore, there is a need for more extensive awareness of the use of this highly promising, non-toxic cancer treatment in the clinical setting. In this review, we provide an elaborate overview of pre-clinical and clinical studies using high-dose IVC as anti-cancer agent, as well as a detailed evaluation of the main known molecular mechanisms involved. A special focus is put on global molecular profiling studies in this respect. In addition, an outlook on future implications of high-dose vitamin C in cancer treatment is presented and recommendations for further research are discussed.

Intravenous Vitamin C for Cancer Therapy - Identifying the Current Gaps in Our Knowledge

The use of intravenous vitamin C (IVC) for cancer therapy has long been an area of intense controversy. Despite this, high dose IVC has been administered for decades by complementary health care practitioners and physicians, with little evidence base resulting in inconsistent clinical practice. In this review we pose a series of questions of relevance to both researchers and clinicians, and also patients themselves, in order to identify current gaps in our knowledge. These questions include: Do oncology patients have compromised vitamin C status? Is intravenous the optimal route of vitamin C administration? Is IVC safe? Does IVC interfere with chemotherapy or radiotherapy? Does IVC decrease the toxic side effects of chemotherapy and improve quality of life? What are the relevant mechanisms of action of IVC? What are the optimal doses, frequency, and duration of IVC therapy? Researchers have made massive strides over the last 20 years and have addressed many of these important aspects, such as the best route for administration, safety, interactions with chemotherapy, quality of life, and potential mechanisms of action. However, we still do not know the answers to a number of fundamental questions around best clinical practice, such as how much, how often and for how long to administer IVC to oncology patients. These questions point the way forward for both basic research and future clinical trials.

A novel osteoporosis model with ascorbic acid deficiency in Akr1A1 gene knockout mice

The AKR1A1 protein is a member of the aldo-keto reductase superfamily that is responsible for the conversion of D-glucuronate to L-gulonate in the ascorbic acid (vitamin C) synthesis pathway. In a pCAG-eGFP transgenic mouse line that was produced by pronuclear microinjection, the integration of the transgene resulted in a 30-kb genomic DNA deletion, including the Akr1A1 gene, and thus caused the knockout (KO) of the Akr1A1 gene and targeting of the eGFP gene. The Akr1A1 KO mice (Akr1A1eGFP/eGFP) exhibited insufficient serum ascorbic acid levels, abnormal bone development and osteoporosis. Using micro-CT analysis, the results showed that the microarchitecture of the 12-week-old Akr1A1eGFP/eGFP mouse femur was shorter in length and exhibited less cortical bone thickness, enlargement of the bone marrow cavity and a complete loss of the trabecular bone in the distal femur. The femoral head and neck of the proximal femur also showed a severe loss of bone mass. Based on the decreased levels of serum osteocalcin and osteoblast activity in the Akr1A1eGFP/eGFP mice, the osteoporosis might be caused by impaired bone formation. In addition, administration of ascorbic acid to the Akr1A1eGFP/eGFP mice significantly prevented the condition of osteoporotic femurs and increased bone formation. Therefore, through ascorbic acid administration, the Akr1A1 KO mice exhibited controllable osteoporosis and may serve as a novel model for osteoporotic research.

Coadministration of a Gloriosa superba extract improves the in vivo antitumoural activity of gemcitabine in a murine pancreatic tumour model

BACKGROUND

Gloriosa superba L. (glory lily, Colchicaceae) contains colchicine, and related alkaloids such as 3-O-demethylcolchicine and its glycoside colchicoside. Previously the in vivo efficacy of a crude extract and a colchicine-poor / colchicoside-rich extract of G. superba seeds was shown in a murine model of pancreatic adenocarcinoma.

HYPOTHESIS/PURPOSE

The efficacy can be improved without obvious signs of toxicity by increasing the treatment dose; the efficacy of gemcitabine can be improved by coadministration of a Gloriosa superba extract.

STUDY DESIGN

A survival experiment was carried out in a murine model of pancreatic adenocarcinoma and the semi-long-term toxicity of both G. superba extracts was determined; a combination therapy with gemcitabine was evaluated.

METHODS

A crude ethanolic extract (GS) and a colchicine-poor / colchicoside-rich extract (GS2B) were prepared, containing 3.22% colchicine, 2.52% colchicoside and 1.52% 3-O-demethylcolchicine (GS), and 0.07%, 2.26% and 0.46% (m/m) (GS2B). They were evaluated in a murine model of pancreatic adenocarcinoma at a dose of 4.5mg/kg (p.o., daily) total content of colchicine and derivatives during 3 weeks, or at 3.0mg/kg (p.o., daily) combined with gemcitabine (60mg/kg, i.p., 3x/week) during 54 days.

RESULTS

A significant effect in tumour growth over time was observed for gemcitabine and the combination therapy compared to the control group. No significant difference was observed for the groups treated with colchicine and both extracts. However, combination therapy was significantly better than the monotherapy with gemcitabine. Moreover, survival analysis showed a significant prolongation of the survival of the groups treated with gemcitabine and the combination therapy. A slight difference in survival was observed between gemcitabine and the combination therapy, the latter one being slightly better. No significant prolongation of survival was observed for the extracts and colchicine compared to the control group.

CONCLUSION

Although a relevant tumour growth inhibition and a difference of relative tumour volume compared to the control group were observed on day 11, and a slightly longer survival was noticed for GS2B, the most important conclusion from this study is that the crude G. superba extract (GS) might have an added value combined with gemcitabine in the treatment of pancreatic tumours.

Impacto da suplementação de vitamina C sobre níveis de peroxidação lipídica e glutationa reduzida em tecido hepático de camundongos com imunossupressão induzida por ciclofosfamida

RESUMO Objetivo: Investigar os efeitos da vitamina C sobre níveis de peroxidação lipídica e glutationa reduzida em tecido hepático de camundongos imunossuprimidos por ciclofosfamida. Métodos: O estudo foi realizado em camundongos Swiss, fêmeas, com 45 dias de idade, separados em quatro grupos com oito animais cada. Grupos: controle (água destilada), vitamina C (50 mg/kg), ciclofosfamida (100 + 150 mg/kg) e tratamento (vitamina C 50 mg/kg + ciclofosfamida 100 +150 mg/kg). Todas as aplicações foram via intraperitoneal. O ensaio biológico teve duração de seis dias, sendo o sétimo a eutanásia dos animais. As análises bioquímicas de peroxidação lipídica (quantificação de substâncias reativas ao ácido tiobarbitúrico) e glutationa reduzida (estimativa de tiois não proteicos) foram realizadas em tecido hepático. Resultados: A ciclofosfamida causou aumento significativo (p<0,0001) nos níveis de peroxidação lipídica. Não foram observadas alterações significativas nos grupos tratados com vitamina C. A ciclofosfamida por si só, não alterou níveis de glutationa reduzida. A vitamina C causou a redução do nível de glutationa reduzida em relação ao controle tanto nos animais que receberam ciclofosfamida quanto nos que não receberam. No entanto, nos grupos tratados com o quimioterápico houve uma interação entre a droga e a vitamina, ou seja, o quimioterápico intensificou a diminuição da glutationa reduzida provocada pela vitamina C. Conclusão: A ciclofosfamida, na dose e período utilizados, foi capaz de induzir o dano oxidativo verificado pelo aumento da peroxidação lipídica. A vitamina C, na dose de 50 mg/kg de peso, não apresentou potencial para proteger contra o dano oxidativo provocado pelo quimioterápico.

"Lassie," "Toto," and fellow pet dogs: poised to lead the way for advances in cancer prevention

Cancer causes substantial morbidity and takes the lives of over 8 million people worldwide each year. Advances in cancer prevention research are crucial, and animal models are key to this. There are many valuable experimentally induced cancer models, but these do not fully meet the needs for cancer prevention studies. Pet dogs with risks for naturally occurring cancer can fill important gaps in cancer prevention research. Using invasive urothelial carcinoma (iUC) as an example, the advantages of utilizing pet dogs include: (1) close similarities between dogs and humans in carcinogenesis, molecular and cellular features, invasive and metastatic behavior, and response to treatment, thus providing high relevance for comparative studies, (2) shared environment between dogs and humans to help identify not-yet-known environmental iUC risks, (3) strong breed-associated risk (5- to 21-fold increased risk compared with mixed breeds) that facilitates investigation of gene-environment interactions, screening, and early intervention, (4) large size of dogs (versus rodents) that allows collection of fluids and tissues via cystoscopy, and detailed imaging at multiple time points, and (5) acceptance for studies in which each participating dog can benefit while enjoying life in their family environment, and in which findings will help other dogs and humans. An ongoing 3-year study in Scottish Terriers (comparable to a 15- to 20-year study in humans) is aimed at defining genetic and environmental risk factors for iUC, effective methods for screening/early detection, and a successful secondary cancer prevention approach with very promising results to date. Pet dogs can indeed propel cancer prevention research.

Molecular mechanisms of pharmacological doses of ascorbate on cancer cells

Intravenous application of high-dose ascorbate (vitamin C) has been used in complementary medicine since the 1970s to treat cancer patients. In recent years it became evident that high-dose ascorbate in the millimolar range bears selective cytotoxic effects on cancer cells in vitro and in vivo. This anticancer effect is dose dependent, catalyzed by serum components and mediated by reactive oxygen species and ascorbyl radicals, making ascorbate a pro-oxidative pro-drug that catalyzes hydrogen peroxide production in tissues instead of acting as a radical scavenger. It further depends on HIF-1 signaling and oxygen pressure, and shows a strong epigenetic signature (alteration of DNA-methylation and induction of tumor-suppressing microRNAs in cancer cells). The detailed understanding of ascorbate-induced antiproliferative molecular mechanisms warrants in-depth preclinical evaluation in cancer-bearing animal models for the optimization of an efficacious therapy regimen (e.g., combination with hyperbaric oxygen or O2-sensitizers) that subsequently need to be evaluated in clinical trials.