Potential antitumor activity of garlic against colorectal cancer: focus on the molecular mechanisms of action

PURPOSE

The aim of this review is to highlight the potential of garlic phytoconstituents as antitumor agents in colorectal cancer management based on their molecular mechanisms of action, while asking if their consumption, as part of the human diet, might contribute to the prevention of colorectal cancer.

METHODS

To gather information on appropriate in vitro, in vivo and human observational studies on this topic, the keywords "Allium sativum", "garlic", "colorectal cancer", "antitumor effect", "in vitro", "in vivo", "garlic consumption" and "colorectal cancer risk" were searched in different combinations in the international databases ScienceDirect, PubMed and Google Scholar. After duplicate and reviews removal, 61 research articles and meta-analyses published between 2000 and 2022 in peer-reviewed journals were found and included in this review.

RESULTS

Garlic (Allium sativum) proves to be a rich source of compounds with antitumor potential. Garlic-derived extracts and several of its individual constituents, especially organosulfur compounds such as allicin, diallyl sulfide, diallyl disulfide, diallyl trisulfide, diallyl tetrasulfide, allylmethylsulfide, S-allylmercaptocysteine, Z-ajoene, thiacremonone and Se-methyl-L-selenocysteine were found to possess cytotoxic, cytostatic, antiangiogenic and antimetastatic activities in different in vitro and in vivo models of colorectal cancer. The molecular mechanisms for their antitumor effects are associated with the modulation of several well-known signaling pathways involved in cell cycle progression, especially G1-S and G2-M transitions, as well as both the intrinsic and extrinsic apoptotic pathways. However, even though in various animal models some of these compounds have chemopreventive effects, based on different human observational studies, a diet rich in garlic is not consistently associated with a lower risk of developing colorectal cancer.

CONCLUSION

Independent of the impact of garlic consumption on colorectal cancer initiation and promotion in humans, its constituents might be good candidates for future conventional and/or complementary therapies, based on their diverse mechanisms of action.

Phytochemical Profile and Selective Cytotoxic Activity of a Solanum bulbocastanum Dun. Methanolic Extract on Breast Cancer Cells

Solanum bulbocastanum is a wild potato species, intensively used in potato breeding programs due to its resistance to environmental factors. Thus, its biochemical profile and putative human health-related traits might be transferred into potato cultivars aimed for consumption. This study aims to assess the phytochemical profile and the selective cytotoxicity of an S. bulbocastanum extract against breast cancer cells. Dry leaves were subjected to ultrasonication-assisted extraction in methanol [70%]. The phenolic and glycoalkaloid profiles were determined by HPLC-PDA/-ESI+-MS. The volatile profile was investigated by nontargeted ITEX/GC-MS. The extract was tested against three breast cancer cell lines (MCF7, MDA-MB-231, HS578T) and a healthy cell line (HUVEC) by the MTT assay, to assess its selective cytotoxicity. The phenolic profile of the extract revealed high levels of phenolic acids (5959.615 µg/mL extract), and the presence of flavanols (818.919 µg/mL extract). The diversity of the volatile compounds was rather low (nine compounds), whereas no glycoalkaloids were identified, only two alkaloid precursors (813.524 µg/mL extract). The extract proved to be cytotoxic towards all breast cancer cell lines (IC₅₀ values between 139.1 and 356,1 µg/mL), with selectivity coefficients between 1.96 and 4.96 when compared with its toxicity on HUVECs. Based on these results we conclude that the exerted cytotoxic activity of the extract is due to its high polyphenolic content, whereas the lack of Solanaceae-specific glycoalkaloids might be responsible for its high selectivity against breast cancer cells in comparison with other extract obtained from wild Solanum species. However, further research is needed in order to assess the cytotoxicity of the individual compounds found in the extract, as well as the anti-tumor potential of the S. bulbocastanum tubers.

Breast Cancer-Delivered Exosomal miRNA as Liquid Biopsy Biomarkers for Metastasis Prediction: A Focus on Translational Research with Clinical Applicability

Metastasis represents the most important cause of breast cancer-associated mortality. Even for early diagnosed stages, the risk of metastasis is significantly high and predicts a grim outcome for the patient. Nowadays, efforts are made for identifying blood-based biomarkers that could reliably distinguish patients with highly metastatic cancers in order to ensure a closer follow-up and a more personalized therapeutic method. Exosomes are nano vesicles secreted by cancer cells that can transport miRNAs, proteins, and other molecules and deliver them to recipient cells all over the body. Through this transfer, cancer cells modulate their microenvironment and facilitate the formation of the pre-metastatic niche, leading to sustained progression. Exosomal miRNAs have been extensively studied due to their promising potential as prognosis biomarkers for metastatic breast cancer. In this review, we tried to depict an overview of the existing literature regarding exosomal miRNAs that are already validated as potential biomarkers, and which could be immediately available for the clinic. Moreover, in the last section, we highlighted several miRNAs that have proven their function in preclinical studies and could be considered for clinical validation. Considering the lack of standard methods for evaluating exosomal miRNA, we also discussed the challenges and the technical aspects underlying this issue.

Chemical Structure, Sources and Role of Bioactive Flavonoids in Cancer Prevention: A Review

There has been a major shift in the collective mindset around the world in recent decades, both in terms of food and in terms of the treatment of chronic diseases. Increasing numbers of people are choosing to prevent rather than treat, which is why many consumers are choosing plant-based diets, mainly due to their bioactive compounds. A significant case of bioactive compound is flavonoids-a wide subclass of an even wider class of phytochemicals: polyphenols. Flavonoids are a broad topic of study for researchers due to their potential in the prevention and treatment of a broad range of cancers. The aim of this review is to inform/update the reader on the diversity, accessibility and importance of flavonoids as biomolecules that are essential for optimal health, focusing on the potential of these compounds in the prevention of various types of cancer. Along with conventional sources, this review presents some of the possible methods for obtaining significant amounts of flavonoids based on a slightly different approach, genetic manipulation.

Critical Aspects Concerning the Development of a Pooling Approach for SARS-CoV-2 Diagnosis Using Large-Scale PCR Testing

The primary approach to controlling the spread of the pandemic SARS-CoV-2 is to diagnose and isolate the infected people quickly. Our paper aimed to investigate the efficiency and the reliability of a hierarchical pooling approach for large-scale PCR testing for SARS-CoV-2 diagnosis. To identify the best conditions for the pooling approach for SARS-CoV-2 diagnosis by RT-qPCR, we investigated four manual methods for both RNA extraction and PCR assessment targeting one or more of the RdRp, N, S, and ORF1a genes, by using two PCR devices and an automated flux for SARS-CoV-2 detection. We determined the most efficient and accurate diagnostic assay, taking into account multiple parameters. The optimal pool size calculation included the prevalence of SARS-CoV-2, the assay sensitivity of 95%, an assay specificity of 100%, and a range of pool sizes of 5 to 15 samples. Our investigation revealed that the most efficient and accurate procedure for detecting the SARS-CoV-2 has a detection limit of 2.5 copies/PCR reaction. This pooling approach proved to be efficient and accurate in detecting SARS-CoV-2 for all samples with individual quantification cycle (Cq) values lower than 35, accounting for more than 94% of all positive specimens. Our data could serve as a comprehensive practical guide for SARS-CoV-2 diagnostic centers planning to address such a pooling strategy.

Extracts of the Wild Potato Species Solanum chacoense on Breast Cancer Cells: Biochemical Characterization, In Vitro Selective Cytotoxicity and Molecular Effects

Solanum chacoense (wild potato) is intensively used in breeding, its biochemical profile and putative human health-related traits being transferred into potato cultivars aimed for consumption. The goal of this study was to evaluate the biochemical profile and the anti-tumor potential of methanolic extracts obtained from S. chacoense leaves and tubers against three breast cancer cell lines in comparison to healthy endothelial cells (HUVEC). The biochemical profile of the extracts was determined by HPLC-PDA/-ESI⁺-MS and ITEX/GC-MS, the selective cytotoxicity by MTT assay whereas RT-qPCR was used to evaluate the expression of proliferation- and apoptosis-related genes. Both extracts proved to be rich in phenolic acids and volatile compounds, the leaf extract also containing glycoalkaloids. Both extracts proved to be cytotoxic for breast cancer cell lines, with IC₅₀ values varying between 132.9 and 390.7 µg/ml. Both extracts had selective cytotoxicity against MCF7 cell line in comparison to HUVECs (selectivity coefficients >2.3). The treatment with the extracts induced overexpression of the pro-apoptotic gene BAX¸ down-regulation of the anti-apoptotic gene BCL-2 and the pro-proliferation genes NFkB, CCND1, and STAT3. Thus S. chacoense extracts proved to be rich in compounds with anticancer proprieties and are capable of inducing selective cytotoxicity on MCF7 cell line.

The dual role of tumor necrosis factor-alpha (TNF-α) in breast cancer: molecular insights and therapeutic approaches

BACKGROUND

Breast cancer is the most prevalent cancer among women worldwide and the fifth cause of death among all cancer patients. Breast cancer development is driven by genetic and epigenetic alterations, with the tumor microenvironment (TME) playing an essential role in disease progression and evolution through mechanisms like inflammation promotion. TNF-α is one of the essential pro-inflammatory cytokines found in the TME of breast cancer patients, being secreted both by stromal cells, mainly by tumor-associated macrophages, and by the cancer cells themselves. In this review, we explore the biological and clinical impact of TNF-α in all stages of breast cancer development. First of all, we explore the correlation between TNF-α expression levels at the tumor site or in plasma/serum of breast cancer patients and their respective clinical status and outcome. Secondly, we emphasize the role of TNF-α signaling in both estrogen-positive and -negative breast cancer cells. Thirdly, we underline TNF-α involvement in epithelial-to-mesenchymal transition (EMT) and metastasis of breast cancer cells, and we point out the contribution of TNF-α to the development of acquired drug resistance.

CONCLUSIONS

Collectively, these data reveal a pro-tumorigenic role of TNF-α during breast cancer progression and metastasis. We systemize the knowledge regarding TNF-α-related therapies in breast cancer, and we explain how TNF-α may act as both a target and a drug in different breast cancer therapeutic approaches. By corroborating the known molecular effects of TNF-α signaling in breast cancer cells with the results from several preclinical and clinical trials, including TNF-α-related clinical observations, we conclude that the potential of TNF-α in breast cancer therapy promises to be of great interest.

Pro-apoptotic genes as new targets for single and combinatorial treatments with resveratrol and curcumin in colorectal cancer

Colorectal cancer (CRC) represents the third most diagnosed type of cancer worldwide with high mortality and an increased incidence rate. Bioactive dietary components such as curcumin and resveratrol have great therapeutic potential as they can modulate a plethora of signaling pathways related to colorectal carcinogenesis. Previous data have demonstrated that curcumin and resveratrol can induce apoptosis in different types of cancer cells. Considering the lack of data on the combinatorial effect of curcumin and resveratrol associated with the induction of apoptosis in colorectal pathology, the main objective of this study is to investigate the impact of single vs. combinatorial treatment of resveratrol and curcumin on their cytotoxic effects, as well as the modulation of several essential pro-apoptotic genes, on two colorectal cancer cell lines (DLD-1 and Caco-2) different in terms of chromosomal stability (MSI and MSS). The cytotoxic effects were evaluated by the MTT assay, the nature of the interaction between curcumin and resveratrol was assessed by the combination index method and the expression levels of key genes involved in the modulation of pro-apoptotic mechanisms were evaluated by RT-qPCR. Our data indicate that the combination treatment of curcumin and resveratrol is more effective in inhibiting the proliferation in a dose-dependent manner, with a synergistic effect for the DLD-1 cell line (CI < 1) and an additive effect for the Caco-2 cell line (CI ≥ 1). The IC50 values for the combination treatment were 71.8 μM (20.5 μM curcumin + 51.3 μM resveratrol) for the DLD-1 cell line and 66.21 μM (18.9 μM curcumin + 47.3 μM resveratrol) for the Caco-2 cell line, respectively. Our data pointed out, for the first time, that several genes involved in the modulation of apoptosis, including PMAIP1, BID, ZMAT3, CASP3, CASP7, and FAS, represent new targets of both singular and combinatorial treatments with resveratrol and curcumin, and also the combinatorial approach of curcumin and resveratrol exhibits a more powerful gene regulating effect compared to single treatment. Considering the beneficial aspects of the combinatorial approach with curcumin and resveratrol on colorectal cancer cells further studies should address the possible pharmacological benefits of using a combination of both dietary agents with different chemotherapeutic drug approaches.

Calendula officinalis: Potential Roles in Cancer Treatment and Palliative Care

A continuous challenge in cancer management is to improve treatment efficacy and to diminish its side effects. Consequently, new conventional and unconventional drugs and bioactive compounds from plants are constantly developed, characterized, and used for in vitro and in vivo models. This review focuses on the antitumor properties of Calendula officinalis, its biological and molecular effects in tumor cells and animal models, as well as its role in cancer palliative care. A systematic review of studies describing the cytotoxic role of C officinalis and its therapeutic role on cancer cells were carried out using the PubMed database. Albeit C officinalis extracts have cytotoxic activity toward different cancer cell lines, a high grade of variation between studies was observed, depending on plant organ subjected to extraction, extraction method, and the cancer cell lines used for each study. Nevertheless, its cytotoxic activity is related to a few bioactive compounds, presenting multiple roles in both activation of proapoptotic proteins and decreasing the expression of the proteins that inhibit cell death. Moreover, due to its anti-genotoxic/protective as well as antitumor and antimetastatic effects proven in animal models, C officinalis could have important future implications in developing novel cancer treatment strategies, while until now it has been used especially for diminishing the side effects of radiotherapy.