Black raspberry restores the expression of the tumor suppressor p120ctn in the oral cavity of mice treated with the carcinogen dibenzo[a,l]pyrene diol epoxide

Rubus Occidentalis and its bioactive compounds against cancer: From molecular mechanisms to translational advances

BACKGROUND

Cancer ranks as the second leading cause of death globally, imposing a significant public health burden. The rise in cancer resistance to current therapeutic agents underscores the potential role of phytotherapy. Black raspberry (BRB, Rubus Occidentalis) is a fruit rich in anthocyanins, ellagic acid, and ellagitannins. Accumulating evidence suggests that BRB exhibits promising anticancer effects, positioning it as a viable candidate for phytotherapy.

PURPOSE

This article aims to review the existing research on BRB regarding its role in cancer prevention and treatment. It further analyzes the effective components of BRB, their metabolic pathways, and the potential mechanisms underlying the fruit's anticancer effects.

METHODS

Ovid MEDLINE, EMBASE, Web of Science, and CENTRAL were searched through the terms of Black Raspberry, Raspberry, and Rubus Occidentali up to January 2023. Two reviewers performed the study selection by screening the title and abstract. Full texts of potentially eligible studies were retrieved to access the details.

RESULTS

Out of the 767 articles assessed, 73 papers met the inclusion criteria. Among them, 63 papers investigated the anticancer mechanisms, while 10 conducted clinical trials focusing on cancer treatment or prevention. BRB was found to influence multiple cancer hallmarks by targeting various pathways. Decomposition of free radicals and regulation of estrogen metabolism, BRB can reduce DNA damage caused by reactive oxygen species. BRB can also enhance the function of nucleotide excision repair to repair DNA lesions. Through regulation of epigenetics, BRB can enhance the expression of tumor suppressor genes, inducing cell cycle arrest, and promoting apoptosis and pyroptosis. BRB can reduce the energy and nutrients supply to the cancer nest by inhibiting glycolysis and reducing angiogenesis. The immune and inflammatory microenvironment surrounding cancer cells can also be ameliorated by BRB, inhibiting cancer initiation and progression. However, the limited bioavailability of BRB diminishes its anticancer efficacy. Notably, topical applications of BRB, such as gels and suppositories, have demonstrated significant clinical benefits.

CONCLUSION

BRB inhibits cancer initiation, progression, and metastasis through diverse anticancer mechanisms while exhibiting minimal side effects. Given its potential, BRB emerges as a promising phototherapeutic agent for cancer treatment.

Berries vs. Disease: Revenge of the Phytochemicals

Secondary metabolites and phytochemicals in plant-based diets are known to possess properties that inhibit the development of several diseases including a variety of cancers of the aerodigestive tract. Berries are currently of high interest to researchers due to their high dietary source of phytochemicals. Black raspberries (BRB), Rubus occidentalis, are of special interest due to their rich and diverse composition of phytochemicals. In this review, we present the most up-to-date preclinical and clinical data involving berries and their phytochemicals in the chemoprevention of a variety of cancers and diseases. BRBs possess a variety of health benefits including anti-proliferative properties, anti-inflammatory activity, activation of pro-cell-death pathways, modulation of the immune response, microbiome modulation, reduction in oxidative stress, and many more. However, little has been done in both preclinical and clinical settings on the effects of BRB administration in combination with other cancer therapies currently available for patients. With the high potential for BRBs as chemopreventive agents, there is a need to investigate their potential in combination with other treatments to improve therapeutic efficacy.

Black Raspberry Extract Enhances Glutathione Conjugation of the Fjord-Region Diol Epoxide Derived from the Tobacco Carcinogen Dibenzo[def,p]chrysene in Human Oral Cells

In a series of previous studies we reported that black raspberry (BRB) powder inhibits dibenzo[a,l]pyrene (DBP)-induced DNA damage, mutagenesis, and oral squamous cell carcinoma (OSCC) development in mice. In the present study, using human oral leukoplakia (MSK-Leuk1) and squamous cell carcinoma (SCC1483) cells, we tested the hypothesis that BRB extract (BRBE) will enhance the synthesis of glutathione (GSH) and in turn increase GSH conjugation of the fjord-region DBP diol epoxide (DBPDE) derived from DBP leading to inhibition of DBP-induced DNA damage. The syntheses of DBPDE-GSH conjugate, DBPDE-dA adduct, and the corresponding isotope-labeled internal standards were performed; LC-MS/MS methods were used for their quantification. BRBE significantly (p < 0.05) increased cellular GSH by 31% and 13% at 6 and 24 h, respectively, in OSCC cells; in MSK-LeuK1 cells, the levels of GSH significantly (p < 0.05) increased by 55% and 22%, at 1 and 6 h. Since BRBE significantly enhanced the synthesis of GSH in both cell types, subsequent experiments were performed in MSK-Leuk1 cells. Western blot analysis was performed to determine the types of proteins involved in the synthesis of GSH. BRBE significantly (p < 0.05) increased the protein expression (2.5-fold) of the glutamate-cysteine ligase catalytic subunit (GCLC) but had no effect on the glutamate-cysteine ligase modifier subunit (GCLM) and glutathione synthetase (GSS). LC-MS/MS analysis showed that pretreatment of cells with BRBE followed by DBPDE significantly (p < 0.05) increased the levels of DBPDE-GSH conjugate (2.5-fold) and decreased DNA damage by 74% measured by assessing levels of DBPDE-dA adduct formation. Collectively, the results of this in vitro study clearly support our hypothesis, and the LC-MS/MS methods developed in the present study will be highly useful in testing the same hypothesis initially in our mouse model and ultimately in smokers.

Black raspberry extract inhibits regulatory T-cell activity in a murine model of head and neck squamous cell carcinoma chemoprevention

Head and neck squamous cell carcinomas (HNSCC) are one of the most diagnosed malignancies globally, with a 5-year survival rate of approximately 40% to 50%. Current therapies are limited to highly invasive surgery, aggressive radiation, and chemotherapies. Recent reports have demonstrated the potential phytochemical properties of black raspberries in inhibiting the progression of various cancers including HNSCCs. However, the effects of black raspberry extracts on immune cells of the tumor microenvironment, specifically regulatory T cells during HNSCC, have not been investigated. We used a mouse model of 4-nitroquinoline-1-oxide (4NQO) chemically induced HNSCC carcinogenesis to determine these effects. C57BL/6 mice were exposed to 4NQO for 16 weeks and regular water for 8 weeks. 4NQO-exposed mice were fed the AIN-76A control mouse diet or the AIN76 diet supplemented with black raspberry extract. At terminal sacrifice, tumor burdens and immune cell recruitment and activity were analyzed in the tumor microenvironment, draining lymph nodes, and spleens. Mice fed the BRB extract-supplemented diet displayed decreased tumor burden compared to mice provided the AIN-76A control diet. Black raspberry extract administration did not affect overall T-cell populations as well as Th1, Th2, or Th17 differentiation in spleens and tumor draining lymph nodes. However, dietary black raspberry extract administration inhibited regulatory T-cell recruitment to HNSCC tumor sites. This was associated with an increased cytotoxic immune response in the tumor microenvironment characterized by increased CD8⁺ T cells and enhanced Granzyme B production during BRB extract-mediated HNSCC chemoprevention. Interestingly, this enhanced CD8⁺ T-cell antitumoral response was localized at the tumor sites but not at spleens and draining lymph nodes. Furthermore, we found decreased levels of PD-L1 expression by myeloid populations in draining lymph nodes of black raspberry-administered carcinogen-induced mice. Taken together, our findings demonstrate that black raspberry extract inhibits regulatory T-cell recruitment and promotes cytotoxic CD8 T-cell activity at tumor sites during HNSCC chemoprevention. These results demonstrate the immunomodulatory potential of black raspberry extracts and support the use of black raspberry-derived phytochemicals as a complementary approach to HNSCC chemoprevention and treatment.