In vivo modulation of several anticancer agents by beta-carotene

Natural products as chemo-radiation therapy sensitizers in cancers

Cancer is a devastating disease and is the second leading cause of death worldwide. Surgery, chemotherapy (CT), and/or radiation therapy (RT) are the treatment of choice for most advanced tumors. Unfortunately, treatment failure due to intrinsic and acquired resistance to the current CT and RT is a significant challenge associated with poor patient prognosis. There is an urgent need to develop and identify agents that can sensitize tumor cells to chemo-radiation therapy (CRT) with minimal cytotoxicity to the healthy tissues. While many recent studies have identified the underlying molecular mechanisms and therapeutic targets for CRT failure, using small molecule inhibitors to chemo/radio sensitize tumors is associated with high toxicity and increased morbidity. Natural products have long been used as chemopreventive agents in many cancers. Combining many of these compounds with the standard chemotherapeutic agents or with RT has shown synergistic effects on cancer cell death and overall improvement in patient survival. Based on the available data, there is strong evidence that natural products have a robust therapeutic potential along with CRT and their well-known chemopreventive effects in many solid tumors. This review article reports updated literature on different natural products used as CT or RT sensitizers in many solid tumors. This is the first review discussing CT and RT sensitizers together in cancer.

Oxidative stress in cancer therapy: Friend or enemy?

Excessive cellular oxidative stress is widely perceived as a key factor in pathophysiological conditions and cancer development. Healthy cells use several mechanisms to maintain intracellular levels of reactive oxygen species (ROS) and overall redox homeostasis to avoid damage to DNA, proteins, and lipids. Cancer cells, in contrast, exhibit elevated ROS levels and upregulated protective antioxidant pathways. Counterintuitively, such elevated oxidative stress and enhanced antioxidant defence mechanisms in cancer cells provide a therapeutic opportunity for the development of drugs with different anticancer mechanisms of action (MoA). In this review, oxidative stress and the role of ROS in cells are described. The tumour-suppressive and tumour-promotive functions of ROS are discussed to compare these two different therapeutic strategies (increasing or decreasing ROS to fight cancer). Clinically approved drugs with demonstrated oxidative stress anticancer MoAs are highlighted before describing examples of metal-based anticancer drug candidates causing oxidative stress in cancer cells via novel MoAs.

Carotenoid Intake and Circulating Carotenoids Are Inversely Associated with the Risk of Bladder Cancer: A Dose-Response Meta-analysis

Some evidence indicates that carotenoids may reduce the risk of bladder cancer (BC), but the association is unclear. We conducted a systematic review and meta-analysis of case-control and cohort studies investigating the relation between carotenoid intake or circulating carotenoid concentrations and BC risk in men and women. All relevant epidemiologic studies were identified by a search of PubMed and Scopus databases, and the Cochrane Library from inception to April 2019 with no restrictions. A random-effects model was used to calculate pooled RRs and their 95% CIs across studies for high compared with low categories of intake or circulating concentrations. We also performed a dose-response meta-analysis using the Greenland and Longnecker method and random-effects models. A total of 22 studies involving 516,740 adults were included in the meta-analysis. The pooled RRs of BC for the highest compared with the lowest category of carotenoid intake and circulating carotenoid concentrations were 0.88 (95% CI: 0.76, 1.03) and 0.36 (95% CI: 0.12, 1.07), respectively. The pooled RR of BC for the highest compared with lowest circulating lutein and zeaxanthin concentrations was 0.53 (95% CI: 0.33, 0.84). Dose-response analysis showed that BC risk decreased by 42% for every 1 mg increase in daily dietary β-cryptoxanthin intake (RR: 0.58; 95% CI: 0.36, 0.94); by 76% for every 1 μmol/L increase in circulating concentration of α-carotene (RR: 0.24; 95% CI: 0.08, 0.67); by 27% for every 1 μmol/L increase in circulating concentration of β-carotene (RR: 0.73; 95% CI: 0.57, 0.94); and by 56% for every 1 μmol/L increase in circulating concentrations of lutein and zeaxanthin (RR: 0.44; 95% CI: 0.28, 0.67). Dietary β-cryptoxanthin intake and circulating concentrations of α-carotene, β-carotene, and lutein and zeaxanthin were inversely associated with BC risk. The protocol was registered at PROSPERO as CRD42019133240.

Antioxidant Antagonises Chemotherapeutic Drug Effect in Lung Cancer Cell Line A549

Objective:

This study aimed to find whether antioxidants increase or decrease the effect of chemotherapeutic drug in the in vitro model.

Methods:

Small lung Cancer cell line (A549) was treated with anticancer drug 6-Thioguanine (6-TG) at different concentration viz., 1, 10, 50 and 100μM and the proliferation was measured using MTT assay. The antioxidant N-Acetyl Cysteine (NAC) in different ratios viz., 1mM, 5mM and 10mM were assayed for their effect in proliferation on the A549 cells alone and in combination with 6-TG.

Results:

Our experiment proves that anticancer drug 6-TG decreases the proliferation and the antioxidant NAC enhances the proliferation of A549 cells. Strikingly when co-treated with 6-TG, the antioxidant NAC diminished the proliferation reduction action of 6-TG on A549 cells.

Conclusion:

Our results suggest that antioxidants in fact benefit the tumor cell growth when treated alone and when in combination with anticancer drug, it severely impair the activity of the drug. We propose that extreme care should be taken when prescribing antioxidants alone or in combination with chemotherapeutics.

Antioxidants in Cancer Therapy: Recent Trends in Application of Nanotechnology for Enhanced Delivery

Recently, the occurrence of cancer has significantly increased; it represents the second-most frequent cause of death after cardiovascular diseases. Many dietary antioxidants have shown large impact as effective agents for cancer prevention by reducing oxidative stress, which has been a part in the development of many diseases, including cancer. One of the obstacles in the delivery of antioxidant therapies into the required domain lies in the inadequate delivery of these agents to their intended site of action. Using nanotechnology in delivery of antioxidants leads to increased therapeutic index and higher drug concentration in tumor tissues, thus enhancing anticancer treatment. In this review, we discuss the role of different antioxidants in cancer therapy and their improved therapeutic effect through their formulation using nanotechnology.

An update on the mechanisms related to cell death and toxicity of doxorubicin and the protective role of nutrients

Doxorubicin (DOX), is a very effective chemotherapeutic agent against cancer whose clinical use is limited by toxicity. Different strategies have been proposed to attenuate toxicity, including combined therapy with bioactive compounds. This review update mechanisms of action and toxicity of doxorubicin and the role of nutrients like vitamins (A, C, E), minerals (selenium) and n-3 polyunsaturated fatty acids. Protective activities against DOX toxicity in liver, kidney, skin, bone marrow, testicles or brain have been reported, but these have not been evaluated for all of the reviewed nutrients. In most cases oxidation-related effects were present either, by reducing ROS levels and/or increasing antioxidant defenses. Antiapoptotic and anti-inflammatory mechanisms are also commonly reported. In some cases, interferences with autophagy and calcium homeostasis also have shown to be affected. Notwithstanding, there is a wide variety in duration and doses of treatment tested for both, compounds and DOX, which make difficult to compare the results of the studies. In spite of the reduction of DOX cardiotoxicity in health models, DOX anti-cancer activity in cancer cell lines or xenograft models usually did not result compromised when this has been evaluated. Importantly, clinical studies are needed to confirm all the observed effects.

Antioxidants as precision weapons in war against cancer chemotherapy induced toxicity - Exploring the armoury of obscurity

Cancer is the leading cause of mortality worldwide, accounting for almost 13% of deaths in the world. Among the conventional cancer treatments, chemotherapy is most frequently carried out to treat malignant cancer rather than localised lesions which is amenable to surgery and radiotherapy. However, anticancer drugs are associated with a plethora of side effects. Each drug, within every class, has its own set of adverse reactions which may cause patient incompliance and deterioration of the quality of life. One of the major causes of adverse reactions, especially for drugs targeting DNA, is the excessive production of reactive oxygen species (ROS) and subsequent build up of oxidative stress. To curb these undesired side effects, several dietary supplements have been tested, amongst which antioxidants have gained increasing popularity as adjuvant in chemotherapy. However, many oncologists discourage the use of antioxidant rich food supplements because these may interfere with the modalities which kill cancer by generating free radicals. In the present review, all studies reporting concomitant use of several antioxidants with chemotherapy are indiscriminately included and discussed impartially.

The effect of supplementation of thirteen different antioxidants and their analogues as a single agent or in combination with chemotherapy has been compiled in this article. The present review encompasses a total of 174 peer-reviewed original articles from 1967 till date comprising 93 clinical trials with a cumulative number of 18,208 patients, 56 animal studies and 35 in vitro studies. Our comprehensive data suggests that antioxidant has superior potential of ameliorating chemotherapeutic induced toxicity. Antioxidant supplementation during chemotherapy also promises higher therapeutic efficiency and increased survival times in patients.

Protective effects of curcumin against doxorubicin-induced toxicity and resistance: A review

Doxorubicin (DOX)-induced toxicity and resistance are major obstacles in chemotherapeutic approaches. Despite effective in the treatment of numerous malignancies, some clinicians have voiced concern that DOX has the potential to cause debilitating consequences in organ tissues, especially the heart. The mechanisms of toxicity and resistance are respectively related to induction of reactive oxygen species (ROS) and up-regulation of ATP-binding cassette (ABC) transporter. Curcumin (CUR) with several biological and pharmacological properties is expected to restore DOX-mediated impairments to tissues. This review is intended to address the current knowledge on DOX adverse effects and CUR protective actions in the heart, kidneys, liver, brain, and reproductive organs. Coadministration of CUR and DOX is capable of ameliorating DOX toxicity pertained to antioxidant, apoptosis, autophagy, and mitochondrial permeability.

Coenzyme Q10 for Prevention of Anthracycline-Induced Cardiotoxicity

Preclinical and clinical studies suggest that anthracycline-induced cardiotoxicity can be prevented by administering coenzyme Q10 during cancer chemotherapy that includes drugs such as doxorubicin and daunorubicin. Studies further suggest that coenzyme Q10 does not interfere with the antineoplastic action of anthracyclines and might even enhance their anticancer effects. Preventing cardiotoxicity might allow for escalation of the anthracycline dose, which would further enhance the anticancer effects. Based on clinical investigation, although limited, a cumulative dose of doxorubicin of up to 900 mg/m2, and possibly higher, can be administered safely during chemotherapy as long as coenzyme Q10 is administered concurrently. The etiology of the dose-limiting cardiomyopathy that is induced by anthracyclines can be explained by irreversible damage to heart cell mitochondria, which differ from mitochondria of other cells in that they possess a unique enzyme on the inner mitochondrial membrane. This enzyme reduces anthracyclines to their semiquinones, resulting in severe oxidative stress, disruption of mitochondrial energetics, and irreversible damage to mitochondrial DNA. Damage to mitochondrial DNA blocks the regenerative capability of the organelle and ultimately leads to apoptosis or necrosis of myocytes. Coenzyme Q10, an essential component of the electron transport system and a potent intracellular antioxidant, appears to prevent damage to the mitochondria of the heart, thus preventing the development of anthracycline-induced cardiomyopathy.

Effect of α-tocopheryl succinate on the molecular damage induced by indomethacin in C6 glioma cells

Indomethacin is a member of the non-steroidal anti-inflammatory drug (NSAID) class, which has great potential for use in the treatment of glioma. However, it induces the generation of reactive oxygen species (ROS) and causes molecular damage while inducing its effects. Vitamin E is widely used in the complementary therapy of cancers. The main goal of the present study was to investigate the effects of α-tocopheryl succinate (α-TOS) against the oxidative damage induced by indomethacin in C6 glioma cells. Cells were treated with 10 μM α-TOS alone or in combination with 200 μM indomethacin for two days. The intracellular ROS level, molecular damage as revealed by lipid peroxidation and protein carbonyl formation, and the COX activity in C6 glioma cells were measured. Treatment of the cells with α-TOS and indomethacin, alone or in combination, caused the levels of ROS generation and protein damage to increase, but protected against lipid peroxidation and reduced COX activity.

Oxidative stress on cardiotoxicity after treatment with single and multiple doses of doxorubicin

The mechanism of doxorubicin (DOX)-induced cardiotoxicity remains controversial. Wistar rats ( n = 66) received DOX injections intraperitoneally and were randomly assigned to 2 experimental protocols: (1) rats were killed before (−24 h, n = 8) and 24 h after (+24 h, n = 8) a single dose of DOX (4 mg/kg body weight) to determine the DOX acute effect and (2) rats ( n = 58) received 4 injections of DOX (4 mg/kg body weight/week) and were killed before the first injection (M0) and 1 week after each injection (M1, M2, M3, and M4) to determine the chronological effects. Animals used at M0 ( n = 8) were also used at moment −24 h of acute study. Cardiac total antioxidant performance (TAP), DNA damage, and morphology analyses were carried out at each time point. Single dose of DOX was associated with increased cardiac disarrangement, necrosis, and DNA damage (strand breaks (SBs) and oxidized pyrimidines) and decreased TAP. The chronological study showed an effect of a cumulative dose on body weight ( R = −0.99, p = 0.011), necrosis ( R = 1.00, p = 0.004), TAP ( R = 0.95, p = 0.049), and DNA SBs ( R = −0.95, p = 0.049). DNA SBs damage was negatively associated with TAP ( R = −0.98, p = 0.018), and necrosis ( R = −0.97, p = 0.027). Our results suggest that oxidative damage is associated with acute cardiotoxicity induced by a single dose of DOX only. Increased resistance to the oxidative stress is plausible for the multiple dose of DOX. Thus, different mechanisms may be involved in acute toxicity versus chronic toxicity.

Effect of β-carotene on cancer cell stemness and differentiation in SK-N-BE(2)C neuroblastoma cells

Neuroblastoma is a solid tumor often diagnosed in childhood. While there have been intense efforts to develop a treatment for neuroblastoma, current therapies remain unsuccessful due to high rate of resistance and metastasis. Most cancers originate from a subset of self-renewing cells, primarily cancer stem cells (CSCs), which establish a tumor through continuous self-renewal and differentiation. The successful elimination of CSCs is an important goal in the development of effective strategies to achieve complete remission for cancers. Although β-carotene has been associated with several anticancer mechanisms, the efficacy of β-carotene against CSCs remains unclear. In the present study, β-carotene was shown to reduce cell growth and induce neuronal cell differentiation, concomitant with a marked increase in the phosphorylation of extracellular signal-regulated kinases (ERK) (p42/p44). More importantly, β-carotene inhibited self-renewal characteristics of CSCs and decreased expression of several stem cell markers. Levels of mRNA and protein of Drosophila delta-like 1 homolog (Drosophila) (DLK1) were downregulated following treatment with β-carotene. In addition, knockdown of DLK1 by siRNA enhanced the inhibitory effect of β-carotene on colony formation of neuroblastoma cells. β-carotene also potentiated the effect of cisplatin on the self-renewal characteristics of CSCs in neuroblastoma, revealing that β-carotene has the capacity to resensitize cells to cisplatin cytotoxicity by directly targeting CSCs. In conclusion, β-carotene was shown to strongly increase the anticancer efficacy against neuroblastoma cancer stem-like cells. Moreover, these results suggest that the targeting of CSCs is a novel mechanism of β-carotene. Thus, β-carotene is a potential chemotherapeutic reagent for this cancer.

Use of prescription and nonprescription medications and supplements by cancer patients during chemotherapy: questionnaire validation

BACKGROUND

Cancer patients take medications for coexisting disease and self-medicate with over-the-counter drugs (OTCs). A complete analysis of the use of prescription drugs, OTCs, and supplements during cancer treatment has never been done.

METHODS

The study developed and validated a self-administered questionnaire on the use of concomitant medications by patients undergoing treatment with chemotherapy. The questionnaire listed 510 prescription medications, OTCs, and supplements (including vitamins, minerals, and herbs). Fifty-two subjects completed the questionnaire while visiting the infusion clinic to receive chemotherapy. On a subsequent visit the subjects brought their medications to the clinic and a pharmacist reviewed their completed questionnaire.

RESULTS

Ninety-six percent of the subjects reported taking prescription medications within 3 days prior to chemotherapy, 71% reported taking OTCs and 69% reported use of supplements. The subjects took an average of 5.5 (range 0-13) prescription drugs, 2.2 (0-20) OTCs, and 1.9 (0-11) supplements. Twenty-one drugs were each taken by at least 10% of the subjects. Acetaminophen was taken by 59.6% of the subjects. One subject reported taking five acetaminophen-containing drugs. The questionnaire's sensitivity was 92.0%, specificity 99.9%.

CONCLUSION

Within 3 days prior to chemotherapy, subjects took an average of 9.6 concomitant medications, many of which alter drug metabolism and or disposition. In clinical trials, multivariate analysis of all concomitant medications could add to clinically relevant data to identify drug interactions that negate or potentiate the efficacy of cancer treatment regimens. In some instances, apparent resistance of tumors to chemotherapy may be the result of drug interactions.

Doxorubicin as an antioxidant: maintenance of myocardial levels of lycopene under doxorubicin treatment

The mechanism of doxorubicin-induced cardiotoxicity remains controversial. Wistar rats (n=96) were randomly assigned to a control (C), lycopene (L), doxorubicin (D), or doxorubicin+lycopene (DL) group. The L and DL groups received lycopene (5 mg/kg body wt/day by gavage) for 7 weeks. The D and DL groups received doxorubicin (4 mg/kg body wt intraperitoneally) at 3, 4, 5, and 6 weeks and were killed at 7 weeks for analyses. Myocardial tissue lycopene levels and total antioxidant performance (TAP) were analyzed by HPLC and fluorometry, respectively. Lycopene metabolism was determined by incubating (2)H(10)-lycopene with intestinal mucosa postmitochondrial fraction and lipoxygenase and analyzed with HPLC and APCI mass spectroscopy. Myocardial tissue lycopene levels in DL and L were similar. TAP adjusted for tissue protein were higher in myocardium of D than those of C (P=0.002). Lycopene metabolism study identified a lower oxidative cleavage of lycopene in D as compared to those of C. Our results showed that lycopene was not depleted in myocardium of lycopene-supplemented rats treated with doxorubicin and that higher antioxidant capacity in myocardium and less oxidative cleavage of lycopene in intestinal mucosa of doxorubicin-treated rats suggest an antioxidant role of doxorubicin rather than acting as a prooxidant.

Dietary carotenoids and genetic instability modify bladder cancer risk

In vitro and in vivo studies have shown that carotenoid supplementation is associated with decreased DNA damage, but the role of dietary carotenoids in cancer risk remains controversial because epidemiologic studies have yielded conflicting results. Limited data exist regarding the role of dietary carotenoids in the context of constitutional genetic instability in cancer risk. This case-control study estimated dietary carotenoid intake [microg/(kJ . d)] from a FFQ for 423 patients with bladder cancer and 467 healthy controls, and quantified baseline and benzo[a]pyrene diol epoxide (BPDE)- and gamma-radiation-induced DNA damage in the peripheral blood lymphocytes using the comet assay. Overall, intake of total carotenoids was lower (P < 0.01) for bladder cancer cases (mean +/- SD: 1273.4 +/- 688.9) compared with healthy controls (1501.3 +/- 791.5). When categorized into quartiles, there was an inverse association between increasing levels of carotenoid intake and bladder cancer risk with greatest protective effect [odds ratio (OR) = 0.56, 95% CI, 0.37-0.85] in the quartile with the highest level of intake. Baseline and mutagen-induced DNA damage was significantly higher in cases than in controls; when analyzed jointly with carotenoid intake, high DNA damage and low carotenoid intake were associated with the highest risk. For example, with high baseline DNA damage and low total carotenoid intake, the OR was 3.08 (95% CI, 1.64-5.77); with high baseline DNA damage and high total carotenoid intake, the risk was somewhat attenuated (OR = 2.49, 95% CI, 1.28-4.84). The risk was decreased further for low baseline DNA damage and low total carotenoid intake (OR = 2.18; 95% CI, 1.13-4.22). This study provides evidence of a preventive role for carotenoids in bladder cancer, and these data may have important implications for cancer prevention, especially for individuals susceptible to DNA damage.

The use of antioxidants with first-line chemotherapy in two cases of ovarian cancer

OBJECTIVE

Because of poor overall survival in advanced ovarian malignancies, patients often turn to alternative therapies despite controversy surrounding their use. Currently, the majority of cancer patients combine some form of complementary and alternative medicine with conventional therapies. Of these therapies, antioxidants, added to chemotherapy, are a frequent choice.

METHODS

For this preliminary report, two patients with advanced epithelial ovarian cancer were studied. One patient had Stage IIIC papillary serous adenocarcinoma, and the other had Stage IIIC mixed papillary serous and seromucinous adenocarcinoma. Both patients were optimally cytoreduced prior to first-line carboplatinum/paclitaxel chemotherapy. Patient 2 had a delay in initiation of chemotherapy secondary to co-morbid conditions and had evidence for progression of disease prior to institution of therapy. Patient 1 began oral high-dose antioxidant therapy during her first month of therapy. This consisted of oral vitamin C, vitamin E, beta-carotene, coenzyme Q-10 and a multivitamin/mineral complex. In addition to the oral antioxidant therapy, patient 1 added parenteral ascorbic acid at a total dose of 60 grams given twice weekly at the end of her chemotherapy and prior to consolidation paclitaxel chemotherapy. Patient 2 added oral antioxidants just prior to beginning chemotherapy, including vitamin C, beta-carotene, vitamin E, coenzyme Q-10 and a multivitamin/mineral complex. Patient 2 received six cycles of paclitaxel/carboplatinum chemotherapy and refused consolidation chemotherapy despite radiographic evidence of persistent disease. Instead, she elected to add intravenous ascorbic acid at 60 grams twice weekly. Both patients gave written consent for the use of their records in this report.

RESULTS

Patient 1 had normalization of her CA-125 after the first cycle of chemotherapy and has remained normal, almost 3(1/2) years after diagnosis. CT scans of the abdomen and pelvis remain without evidence of recurrence. Patient 2 had normalization of her CA-125 after the first cycle of chemotherapy. After her first round of chemotherapy, the patient was noted to have residual disease in the pelvis. She declined further chemotherapy and added intravenous ascorbic acid. There is no evidence for recurrent disease by physical examination, and her CA-125 has remained normal three years after diagnosis.

CONCLUSION

Antioxidants, when added adjunctively, to first-line chemotherapy, may improve the efficacy of chemotherapy and may prove to be safe. A review of four common antioxidants follows. Because of the positive results found in these two patients, a randomized controlled trial is now underway at the University of Kansas Medical Center evaluating safety and efficacy of antioxidants when added to chemotherapy in newly diagnosed ovarian cancer.

The use of antioxidant therapies during chemotherapy

OBJECTIVE

At the present time, many cancer patients combine some form of complementary and alternative medicine therapies with their conventional therapies. The most common choice of these therapies is the use of antioxidants.

RESULTS

A review of four common antioxidants is undertaken, which includes vitamin E (mixed tocopherols and tocotrienols), beta-carotene (natural mixed carotenoids), vitamin C (ascorbic acid), and vitamin A (retinoic acid). Antioxidants act as electron acceptors as well as therapeutic biologic response modifiers. Despite the fact that chemotherapy-induced formation of free radicals is well-demonstrated, chemotherapy-induced cytotoxicity in general does not seem to depend on formation of reactive oxygen species.

CONCLUSIONS

Currently, evidence is growing that antioxidants may provide some benefit when combined with certain types of chemotherapy. Because of the potential for positive benefits, a randomized controlled trial evaluating the safety and efficacy of adding antioxidants to chemotherapy in newly diagnosed ovarian cancer is underway at the University of Kansas Medical Center.

Anti-oxidant vitamins reduce normal tissue toxicity induced by radio-immunotherapy

Our purpose was to determine whether the administration of anti-oxidant vitamins could reduce dose-limiting toxicity from radio-immunotherapy (RAIT) and thereby allow higher escalation of RAIT doses. Lipophilic vitamins A and E were administered i.p. and hydrophilic vitamin C was administered i.m. for 14 days (3 days pre-RAIT through 11 days post-RAIT) alone or with bone marrow transplantation (BMT) to either BALB/c mice for toxicity studies or to nude mice bearing s.c. GW-39 human colonic cancer xenografts for therapy studies. The maximal tolerated dose (MTD) of RAIT ((131)I-MN14 anti-CEA IgG) that results in no lethality was determined for mice that did not receive vitamins or BMT and those that did receive one or both interventions. Body weight, peripheral white blood cell (pWBC) and platelet (PLT) counts and tumor growth were also measured. Administration of vitamins (equivalent of 3.5 IU/day vitamin A, 0.107 IU/day vitamin E and 4.0 mg/day ascorbic acid) to mice along with BMT increased the MTD by 42% and reduced body weight loss associated with RAIT. Vitamins also reduced the magnitude of RAIT-induced myelosuppression. As early as day 7 after RAIT, vitamins increased WBC counts following both a 400 microCi and a 500 microCi dose. On day 14 after the 400 microCi dose of RAIT (day 7 post-BMT), the additive effect of BMT and vitamin could be detected. Tumor growth was not adversely affected by vitamin administration.

Biomarkers and molecular epidemiology and chemoprevention of oral carcinogenesis

Chemopreventives are chemicals that prevent the formation of cancers such as oral cancer. They can take the form of nutrients or synthetic molecules, and their fundamental characteristic is that they do not produce disease processes that would result in debilitating symptoms. Current evidence indicates that they function by modifying the oxidative state of transforming cells. Biomarkers can take the form of genetic and molecular indicators, which characterize the function of chemopreventives and cancer processes such as oral carcinogenesis. Biomarkers cannot provide all the required information for risk assessment or possible activity of the chemopreventives. Other methods, such as epidemiological analyses and techniques, must be used to enhance our understanding of the risk for oral cancer in human populations. One common epidemiologic method, the questionnaire, helps to determine the use and carcinogenic potential of tobacco and alcohol during oral carcinogenesis. Genetic and molecular changes in human patient populations may result in a reduction in the number and function of tumor suppressor genes. If these changes are to be assessed, the tissues (e.g., buccal mucosa) must be accessible and harvested in a reliable and consistent manner for the acquisition of DNA, mRNA, and protein. Oral tissues provide sufficient quantities of these molecules and, under stringent conditions, the quality required for the isolation of these molecular constituents. In conjunction with epidemiologic techniques, various genotypic polymorphisms, such as glutathione-S-transferase (GSTM1) or cytochrome P450 (CYP450A1), have indicated a loss in carcinogen detoxification or the processing of internal growth control signals. Biomarkers are composed of a large diverse group of genetic and molecular structures. Some of these biomarkers are indicators for programmed cell death (PCD), while others describe malignant tumor growth. Many of these classes of molecules are oxidative-responsive (e.g., tumor suppressor p53, Bcl-2, growth factors, immune-derived proteins, and death-inducing molecules) and induce PCD by triggering a cascade of cysteine proteases and regulators (e.g., caspases, death receptors). This pathway results in cell-cycle alterations and DNA fragmentation. It is hoped that a detailed knowledge of the processes involved in malignant transformation will better define the biomarker-screening tools for oral cancer. These tools will enhance our ability to predict the incidence of cancer, detect early malignant change, and quantitate chemoprevention during oral carcinogenesis. Chemopreventives such as the retinoids have already demonstrated their ability to suppress potential malignant changes in pre-malignant oral leukoplakias and decrease the incidence of second head-and-neck cancer primaries. It is our hope that this review will increase investigators' interest in developing new screening and detection systems for oral cancer.

High doses of multiple antioxidant vitamins: essential ingredients in improving the efficacy of standard cancer therapy

Numerous articles and several reviews have been published on the role of antioxidants, and diet and lifestyle modifications in cancer prevention. However, the potential role of these factors in the management of human cancer have been largely ignored. Extensive in vitro studies and limited in vivo studies have revealed that individual antioxidants such as vitamin A (retinoids), vitamin E (primarily alpha-tocopheryl succinate), vitamin C (primarily sodium ascorbate) and carotenoids (primarily polar carotenoids) induce cell differentiation and growth inhibition to various degrees in rodent and human cancer cells by complex mechanisms. The proposed mechanisms for these effects include inhibition of protein kinase C activity, prostaglandin E1-stimulated adenylate cyclase activity, expression of c-myc, H-ras, and a transcription factor (E2F), and induction of transforming growth factor-beta and p21 genes. Furthermore, antioxidant vitamins individually or in combination enhance the growth-inhibitory effects of x-irradiation, chemotherapeutic agents, hyperthermia, and biological response modifiers on tumor cells, primarily in vitro. These vitamins, individually, also reduce the toxicity of several standard tumor therapeutic agents on normal cells. Low fat and high fiber diets can further enhance the efficacy of standard cancer therapeutic agents; the proposed mechanisms for these effects include the production of increased levels of butyric acid and binding of potential mutagens in the gastrointestinal tract by high fiber and reduced levels of growth promoting agents such as prostaglandins, certain fatty acids and estrogen by low fat. We propose, therefore, a working hypothesis that multiple antioxidant vitamin supplements together with diet and lifestyle modifications may improve the efficacy of standard and experimental cancer therapies.

Contrasting effects of vitamins as modulators of apoptosis in cancer cells and normal cells: a review

Individual vitamins can induce direct apoptosis or indirect apoptosis via cell differentiation in cancer cells; however, they can also stimulate antiapoptotic events in certain cancer cells. These effects depend on the dose, type, and form of vitamins and the type of tumor cells. A mixture of antioxidant vitamins is more effective than individual vitamins, and there is no evidence that such a mixture ever stimulates antiapoptotic events in cancer cells. Vitamins in combination with nonvitamin, direct-acting, apoptotic agents (X-rays, chemotherapeutic agents, and hyperthermia) or in combination with nonvitamin, indirect-acting, apoptotic agents (adenosine 3',5'-cyclic monophosphate, butyric acid, and interferon) produce a greater extent of apoptotic death in cancer cells in culture. Certain antioxidant vitamins may reduce the efficacy of some chemotherapeutic agents on rodent fibrosarcoma cells. In contrast to vitamin-induced apoptosis in cancer cells, normal cells never undergo apoptotic death after treatment with vitamins (not including retinoids). On the contrary, vitamins protect normal cells against apoptosis induced by a certain group of chemicals. The reasons for this differential effect of vitamins on cancer and normal cells are unknown. The genetic regulation of apoptosis in cancer cells has not been adequately defined. Such studies would help in identifying molecular targets that can be used to develop effective doses of vitamins or new drugs to induce apoptosis selectively in cancer cells.

Mechanisms of cancer inhibition by anti-oxidant nutrients

The cancer inhibitory properties of anti-oxidant micronutrients have been well established in experimental animal models and cell culture studies. Human studies have also tended to indicate an inhibition of various forms of cancer and the regression of some precancerous lesions. The biological mechanisms for cancer inhibition and regression are now gradually becoming understood, and the anti-oxidant nutrients appear to act through a number of pathways common to most of the agents studied. These various micronutrients appear to act through a complex group of "common pathways" of anticancer activity based upon three major mechanisms: (1) tumour inhibition by immune cytokines; (2) stimulation of cancer suppressor genes, such as "wild type" p53, and diminished expression or dysregulation of oncogenes such as mutant p53 and H-ras; (3) inhibition of tumour angiogenesis through the inhibition of angiogenesis-stimulating factors such as TGF alpha. Retinoid action differs, in some respects, from other micronutrient anticancer mechanisms and appears to relate to its stimulation of cellular differentiation and resultant apoptosis of neoplastic cells. Combinations of anti-oxidant nutrients have been shown to be synergistic in their anticancer activity, probably due to their optimal anticancer activity at different oxygen potentials. Selectivity in the action on cancer cells, as opposed to normal cells, is a major feature of the anti-oxidant micronutrients.

Cell, tissue and organ culture as in vitro models to study the biology of squamous cell carcinomas of the head and neck

In vitro models are currently being used to study head and neck squamous cell carcinoma (HNSCC). Several hundred HNSCC cell lines have been established by various investigators and used to study a broad spectrum of questions related to head and neck cancer. The head and neck model with respect to multistage carcinogenesis is now complete. Several techniques exist for the culture of normal epithelial cells from the upper aerodigestive tract (UADT). The biology of these UADT cells (oral cavity, oropharynx, hypopharynx and larynx) is being studied. Successful culture of premalignant lesions (dysplastic mucosa, leukoplakia, erythroplakia) has resulted in establishment of a limited number of premalignant cell lines and cell cultures. HPV infection of normal oral epithelial cells for immortalization (approximately premalignant cells) coupled with transformation with carcinogens (malignant cells) has established an experimental model for progression. Two in vivo models for oral carcinogenesis, the 7,12 dimethylbenz(a)anthracene-induced hamster cheek pouch model and the 4-nitroquinoline-N-oxide rat oral model, have been established in culture. Thus, multistage carcinogenesis models have been established from both human tissues and animal models and include cultures of normal, premalignant and malignant cells. Culture techniques for growing dissociated primary tumor cells for short term experimental analysis are being used. The culture of normal or tumor tissue as organ/explant cultures allows for the maintenance of normal cell-cell and cell-matrix interaction, but limits experimentation since these cultures cannot be propagated. Several three dimensional model systems are being used to obtain this histological complexity but allow for experimentation. The ability to culture normal, premalignant and malignant cells coupled with the use of a variety of culture techniques, should allow for the continued growth and experimentation in head and neck cancer research.

Suppression by carotenoids of microcystin-induced morphological changes in mouse hepatocytes

Microcystin-LR is a liver tumor promoter in the okadaic acid class, a group of potent inhibitors of protein phosphatases 1 and 2A. Because of inhibition of protein phosphatases, microcystin-LR induces hyperphosphorylation of cellular proteins, including cytoskeletal proteins--cytokeratins 8 and 18--and causes morphological changes in mouse hepatocytes in primary culture. We studied the effects of carotenoids to antagonize microcystin-LR-induced morphological changes in hepatocytes. beta-carotene (100 nM to 100 microns) suppressed the morphological changes induced by 100 nM microcystin-LR in a dose-dependent manner. Other carotenoids tested exerted similar suppressive effects, although retinoids, such as all-trans retinol, all-trans retinoic acid, and 9-cis retinoic acid, were only weakly suppressive. The relative potency of the suppression correlated significantly with the number of conjugated double bonds in the trans configuration. beta-carotene strongly suppressed the hyperphosphorylation of cellular proteins induced by microcystin-LR without significant changes in the basal phosphorylation level. Other antioxidants, such as alpha-tocopherol, did not protect the cells against microcystin-LR. Taken together, the antagonistic effects of carotenoids against microcystin-LR are difficult to explain by their antioxidant or provitamin A activities. Suppression of the hyperphosphorylation of cellular proteins may be a novel mechanism by which carotenoids inhibit tumor promotion.