A Way Forward for Cancer Chemoprevention: Think Local

Emerging Trends in Cancer Prevention Agent Development

Advances in omics and immunology over the past 20 years have revolutionized the approach to cancer prevention, with the goal now focused on identifying populations at higher risk for developing cancer in their lifetime as a result of either extensive exposure to environmental carcinogens or harboring precancer lesions or inherited genetic mutations that predispose them to specific types of cancer(s). Thus, the naïve idea that cancer could be "prevented" in the general population has evolved to a more practical approach based on the understanding that the target population for preventive agents will be individuals who already have alterations, in gene pathways, whether inherited or environmentally caused, and the goal will be to "intercept" these lesions at the earliest stages in the path from an initial genetic lesion to full-blown cancer. The Division of Cancer Prevention of the National Cancer Institute and the Office of Disease Prevention at the National Institutes of Health recently sponsored the second biennial "Translational Advances in Cancer Preventive Agent Development Meeting," held virtually from September 7-9th. In this Meeting Report, we highlight the scientific sessions of this meeting that covered the most recent advances in preventive agent development that also highlighted these rapidly emerging trends in this research area.

Metformin pretreatment potentiates the antiproliferative action of doxorubicin against breast cancer

OBJECTIVES

The present study aimed to evaluate the effect of metformin pretreatment on the potentiation of antiproliferative action of doxorubicin against breast cancer.

MATERIAL AND METHODS

Female Wistar rats were administered with 7,12-Dimethylbenz(a)anthracene (DMBA) (35mg) in 1mL olive oil subcutaneously beneath the mammary gland. Animals were pretreated with metformin (Met) 200mg/kg two weeks before DMBA administration. DMBA control groups received doxorubicin (Dox) (4mg/kg and 2mg/kg), Met (200mg/kg) alone and in combination with Dox (4mg/kg). Met pre-treated DMBA control groups received Dox 4mg/kg and 2mg/kg.

RESULTS

Met pre-treated groups treated with Dox exhibited a decrease in tumor incidence, tumor volume and increased survival rate than the DMBA group. Organ-to-body weight ratios and histopathology of heart, liver and lungs of Met pre-treated groups treated with Dox showed lesser toxicity than Dox treated DMBA control groups. There was a noteworthy decrease in malondialdehyde levels and a substantial increase in the levels of reduced glutathione together with a significant decrease in the levels of inflammatory markers like IL-6, IL-1β and NF-κB in Met pre-treated groups treated with Dox. Histopathology of breast tumors revealed better control of tumors in Met pre-treated groups treated with Dox than DMBA control group. Immunohistochemistry and real-time PCR data revealed a significant reduction in Ki67 expression in Met pre-treated groups treated with Dox as compared to the DMBA control group.

CONCLUSION

The present study suggests that metformin pretreatment potentiates the antiproliferative action of doxorubicin against breast cancer.

Topical transdermal chemoprevention of breast cancer: where will nanomedical approaches deliver us?

Despite the high incidence of breast cancer, there are few pharmacological prevention strategies for the high-risk population and those that are available have low adherence. Strategies that deliver drugs directly to the breasts may increase drug local concentrations, improving efficacy, safety and acceptance. The skin of the breast has been proposed as an administration route for local transdermal therapy, which may improve drug levels in the mammary tissue, due to both deep local penetration and percutaneous absorption. In this review, we discuss the application of nanotechnology-based strategies for the delivery of well established and new agents as well as drug repurposing using the topical transdermal route to improve the outcomes of preventive therapy for breast cancer.

Exploring potential formulation strategies for chemoprevention of breast cancer: a localized delivery perspective

This review focuses on the various formulation approaches that have been explored to achieve localized delivery in breast cancer. The rationale behind the necessity of localized drug delivery has been extensively reviewed. The review also emphasizes the various possible routes for achieving localized drug delivery. Particularly, different types of nanoplatforms like lipid-based drug carriers, polymeric particles, hydrogels, drug conjugates and other formulation strategies like microneedles and drug-eluting implants, which have been used to increase tumor retention and subsequently halt tumor progression, have been deliberated here. In addition, the significant challenges that may be encountered in the delivery of anticancer drugs and the aspects that require careful evaluation for effective localized delivery of chemotherapeutic agents have been discussed.

Breast cancer worry in higher-risk women offered preventive therapy: a UK multicentre prospective study

Purpose

Women’s worry about developing breast cancer may influence their decision to use preventive therapy. However, the direction of this relationship has been questioned. We prospectively investigated the relationship between breast cancer worry and uptake of preventive therapy. The socio-demographic and clinical factors associated with high breast cancer worry were also investigated.

Methods

Women at increased risk of developing breast cancer were recruited from clinics across England (n = 408). Participants completed a survey on their breast cancer worry, socio-demographic and clinical factors. Uptake of tamoxifen was recorded at 3 months (n = 258 women, 63.2%). Both primary and sensitivity analyses were conducted using different classifications of low, medium and high worry.

Results

39.5% of respondents reported medium breast cancer worry at baseline and 21.2% reported high worry. Ethnic minority women were more likely to report high worry than white women (OR = 3.02, 95%CI 1.02, 8.91, p = 0.046). Women educated below degree level were more likely to report high worry than those with higher education (OR = 2.29, 95%CI 1.28, 4.09, p = 0.005). No statistically significant association was observed between worry and uptake. In the primary analysis, fewer respondents with medium worry at baseline initiated tamoxifen (low worry = 15.5%, medium = 13.5%, high = 15.7%). In the sensitivity analysis, participants with medium worry reported the highest uptake of tamoxifen (19.7%).

Conclusions

No association was observed between worry and uptake, although the relationship was affected by the categorisation of worry. Standardised reporting of the classification of worry is warranted to allow transparent comparisons across cohorts.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10549-021-06183-x.

Assessing the Current State of Lung Cancer Chemoprevention: A Comprehensive Overview

Chemoprevention of lung cancer is thought to significantly reduce the risk of acquiring these conditions in the subpopulation of patients with underlying health issues, such as chronic obstructive pulmonary disorder and smoking-associated lung problems. Many strategies have been tested in the previous decades, with very few translating to successful clinical trials in specific subpopulations of patients. In this review, we analyze these strategies, as well as new approaches that have emerged throughout the last few years, including synthetic lethality concept and microbiome-induced regulation of lung carcinogenesis. Overall, the continuous effort in the area of lung chemoprevention is required to develop practical therapeutical approaches. Given the inconsistency of results obtained in clinical trials targeting lung cancer chemoprevention in various subgroups of patients that differ in the underlying health condition, race, and gender, we believe that individualized approaches will have more promise than generalized treatments.

Chemoprevention of Colorectal Cancer

Although colorectal cancer (CRC) screening has reduced the incidence of and mortality from CRC, chemoprevention strategies have the potential to further reduce CRC incidence and mortality. Chemoprevention agents might be used for average-risk as well as high-risk groups, and to prevent CRC recurrence after therapy. CRC chemoprevention agents that have been studied include aspirin, nonaspirin nonsteroidal anti-inflammatory drugs, statins, agents that target metabolic pathways, and vitamins and minerals. We review the prospect of chemoprevention of CRC, results from preclinical and human studies, challenges, and future directions.

A Phase I Trial of Berberine in Chinese with Ulcerative Colitis

The Chinese natural product, berberine, has biological properties that support its potential efficacy as a colon cancer prevention agent. Its longstanding use in China to treat gastrointestinal tract and rheumatologic disorders is generally regarded as safe, supporting initial investigations in an at-risk population, such as individuals with ulcerative colitis. However, the safety of berberine in this population is not established. Individuals living in China with biopsy-proven ulcerative colitis, ≤grade 2 dysplasia, and with a ulcerative colitis disease activity index (UCDAI) score ≤1 on mesalamine, were randomized 3:1 in a double-blind phase I trial to berberine 900 mg/day or placebo for 3 months, with the primary objective of assessing safety. Blood samples and biopsies of the colorectum, from prespecified locations, were collected prior to and following therapy. Secondary endpoints included changes in UCDAI score, and in tissue and plasma markers of inflammation. Of toxicities at least possibly related, one episode of grade 3 elevation in transaminases and one episode of grade 1 nausea were observed among 12 individuals on berberine, and none were observed among 4 on placebo. The mean plasma berberine concentration was 3.5 nmol/L after berberine treatment, significantly higher than 0.5 nmol/L with placebo. Berberine significantly decreased the Geboes grade in colonic tissue, but had a nonsignificant effect on other tissue or blood biomarkers related to cell growth and inflammation. The combination of berberine and mesalamine is well tolerated in Chinese with ulcerative colitis and may enhance mesalamine's anti-inflammatory effects in colonic tissue.

Evaluation of the STAT3 inhibitor GLG‑302 for the prevention of estrogen receptor‑positive and ‑negative mammary cancers

Signal transducer and activator of transcription 3 (STAT3) plays a key role in the transformation of normal cells to cancerous cells. Although inhibitors of STAT3 have been shown to suppress the growth of multiple cancer types in vitro and in vivo, such agents are of particular interest for the prevention of breast cancer, which affects over 200,000 women and claims more than 40,000 lives in the United States each year. In the present study, we employed the MMTV/Neu transgenic mouse model, which develops estrogen receptor (ER)‑negative, Neu‑overexpressing tumors, and the Sprague‑Dawley (SD) rat model, which develops ER‑positive tumors upon exposure to the carcinogen 7,12‑dimethylbenz[a]anthracene (DMBA), to test the efficacy of the STAT3 inhibitor GLG‑302 in the prevention of mammary cancer. Orally administered GLG‑302 and its trizma salt derivative reduced mammary cancer incidence, multiplicity, and tumor weights in female MMTV/Neu mice, and GLG‑302 reduced tumor multiplicity and weights in female DMBA‑treated rats. Consistent with the mechanism of action of STAT3 inhibitors, the reductions in mammary tumors were correlated with decreases in STAT3 phosphorylation and cell proliferation. These data suggest that GLG‑302 is a novel agent with potential for prevention of mammary cancer and support the further development of STAT3 inhibitors for this cause.

Identifying chemopreventive agents for obesity-associated cancers using an efficient, 3D high-throughput transformation assay

Obesity is associated with ~40% of cancer diagnoses but there are currently no effective preventive strategies, illustrating a need for chemoprevention. We previously demonstrated that fibroblast growth factor 2 (FGF2) from adipose tissue stimulates malignant transformation, as measured by growth in soft agar, the gold-standard in vitro transformation assay. Because the soft agar assay is unsuitable for high throughput screens (HTS), we developed a novel method using 3D growth in ultra-low attachment conditions as an alternative to growth in agar to discover compounds that inhibit transformation. Treating non-tumorigenic, skin epithelial JB6 P⁺ cells with FGF2 stimulates growth in ultra-low attachment conditions analogous to growth in the soft agar. This transformation HTS identified picropodophyllin, an insulin growth factor 1 receptor (IGF1R) inhibitor, and fluvastatin, an HMG-CoA reductase inhibitor, as potential chemopreventive agents. These compounds were validated for efficacy using two non-tumorigenic cell lines in soft agar. Another IGF1R inhibitor and other statins were also tested and several were able to inhibit growth in soft agar. This novel 3D HTS platform is fast, robust and has the potential to identify agents for obesity-associated cancer prevention.

Flaxseed Lignans as Important Dietary Polyphenols for Cancer Prevention and Treatment: Chemistry, Pharmacokinetics, and Molecular Targets

Cancer causes considerable morbidity and mortality across the world. Socioeconomic, environmental, and lifestyle factors contribute to the increasing cancer prevalence, bespeaking a need for effective prevention and treatment strategies. Phytochemicals like plant polyphenols are generally considered to have anticancer, anti-inflammatory, antiviral, antimicrobial, and immunomodulatory effects, which explain their promotion for human health. The past several decades have contributed to a growing evidence base in the literature that demonstrate ability of polyphenols to modulate multiple targets of carcinogenesis linking models of cancer characteristics (i.e., hallmarks and nutraceutical-based targeting of cancer) via direct or indirect interaction or modulation of cellular and molecular targets. This evidence is particularly relevant for the lignans, an ubiquitous, important class of dietary polyphenols present in high levels in food sources such as flaxseed. Literature evidence on lignans suggests potential benefit in cancer prevention and treatment. This review summarizes the relevant chemical and pharmacokinetic properties of dietary polyphenols and specifically focuses on the biological targets of flaxseed lignans. The consolidation of the considerable body of data on the diverse targets of the lignans will aid continued research into their potential for use in combination with other cancer chemotherapies, utilizing flaxseed lignan-enriched natural products.

Acceptability of Localized Cancer Risk Reduction Interventions Among Individuals at Average or High Risk for Cancer

Individuals at high risk for cancer, including those already diagnosed with premalignant lesions, can potentially benefit from chemopreventive interventions to reduce cancer risk. However, uptake and acceptability have been hindered due to the risk of systemic toxicity and other adverse effects. Locally delivered chemopreventive agents, where direct action on the primary organ may limit systemic toxicity, are emerging as an option for high-risk individuals. While a number of clinical trials support the development of chemopreventive agents, it is crucial to understand the factors and barriers that influence their acceptability and use. We conducted 36 focus groups with 198 individuals at average and high risk of breast/ovarian, gynecologic, and head/neck/oral and lung cancers to examine the perceptions and acceptability of chemopreventive agents. Participants' willingness to use chemopreventive agents was influenced by several factors, including perceived risk of cancer, skepticism around prevention, previous knowledge of chemopreventive agents, support from trusted sources of health information, participation in other cancer-related risk-reduction activities, previous experience with similar modalities, cost, regimen, side effects, and perceived effectiveness of the preventive intervention. Our findings indicate that individuals may be more receptive to locally delivered chemopreventive agents if they perceive themselves to be at high risk for cancer and are given the necessary information regarding regimen and side effects to make an informed decision. Clinical trials that collect additional patient-centered data including side effects and how these interventions fit into an individual's lifestyle are imperative to improve uptake of chemopreventive agents.

Intranasal administration of resveratrol successfully prevents lung cancer in A/J mice

Lung cancer is the most lethal cancer in the world. About 80% of lung cancer deaths are linked to tobacco use. As a complement to tobacco control, efficient chemoprevention strategies are needed to tackle lung cancer epidemic. Resveratrol is one of the most studied natural products, notably for its cancer chemoprevention properties. However, its low oral bioavailability has often limited the translation of in vitro activities to in vivo effects. While oral administration of resveratrol effectively inhibited colorectal carcinogenesis, it failed to protect mice from chemically-induced lung carcinogenesis. Therefore, non-invasive parenteral routes must be considered to bring resveratrol to the lungs. In the present study, intranasal administration of a concentrated formulation proved to be a valid method to expose the lungs to a sufficient amount of resveratrol. This formulation was administered three times a week for 25 weeks to A/J mice having 4-[methyl(nitroso)amino]-1-(3-pyridinyl)-1-butanone-induced lung carcinogenesis. Resveratrol-treated mice showed a 27% decrease in tumour multiplicity, with smaller tumours, resulting in 45% decrease in tumour volume/mouse. In vitro investigations highlighted apoptosis as a potential mechanism of action. This study presents an effective way to overcome resveratrol low oral bioavailability, encouraging a reevaluation of its use in future clinical trials.