Doxorubicin and α-Mangostin oppositely affect luminal breast cancer cell stemness evaluated by a new retinaldehyde-dependent ALDH assay in MCF-7 tumor spheroids

Liposome-enabled bufalin and doxorubicin combination therapy for trastuzumab-resistant breast cancer with a focus on cancer stem cells

Breast cancer stem cells (BCSCs) play a key role in therapeutic resistance in breast cancer treatments and disease recurrence. This study aimed to develop a combination therapy loaded with pH-sensitive liposomes to kill both BCSCs and the okbulk cancer cells using trastuzumab-sensitive and resistant human epidermal growth factor receptor 2 positive (HER2+) breast cancer cell models. The anti-BCSCs effect and cytotoxicity of all-trans retinoic acid, salinomycin, and bufalin alone or in combination with doxorubicin were compared in HER2+ cell line BT-474 and a validated trastuzumab-resistant cell line, BT-474R. The most potent anti-BCSC agent was selected and loaded into a pH-sensitive liposome system. The effects of the liposomal combination on BCSCs and bulk cancer cells were assessed. Compared with BT-474, the aldehyde dehydrogenase positive BCSC population was elevated in BT-474R (3.9 vs. 23.1%). Bufalin was the most potent agent and suppressed tumorigenesis of BCSCs by ∼50%, and showed strong synergism with doxorubicin in both BT-474 and BT-474R cell lines. The liposomal combination of bufalin and doxorubicin significantly reduced the BCSC population size by 85%, and inhibited both tumorigenesis and self-renewal, although it had little effect on the migration and invasiveness. The cytotoxicity against the bulk cancer cells was also enhanced by the liposomal combination than either formulation alone in both cell lines (p < 0.001). The liposomal bufalin and doxorubicin combination therapy may effectively target both BCSCs and bulk cancer cells for a better outcome in trastuzumab-resistant HER2+ breast cancer.

Enhancing Tamoxifen Therapy with α-Mangostin: Synergistic Antiproliferative Effects on Breast Cancer Cells and Potential Reduced Endometrial Impact

Breast cancer is the most prevalent neoplasia among women worldwide. For the estrogen receptor-positive (ER+) phenotype, tamoxifen is the standard hormonal therapy; however, it carries the risk of promoting endometrial carcinoma. Hence, we aimed to evaluate the antiproliferative effect of the phytochemical α-mangostin (AM) as a co-adjuvant alongside tamoxifen on breast cancer cells to improve its efficacy while reducing its adverse effects on endometrium. For this, ER+ breast cancer cells (MCF-7 and T-47D) and endometrial cells (N30) were treated with AM, 4-hydroxytamoxifen (4-OH-TMX), and their combination. Cell proliferation was evaluated using sulforhodamine B assay, and the pharmacological interaction was determined through the combination index and the dose reduction index calculation. The genes KCNH1, CCDN1, MKI67, and BIRC5 were amplified by real-time PCR as indicators of oncogenesis, cell cycle progression, cell proliferation, and apoptosis, respectively. Additionally, genes involved in ER signaling were analyzed. In breast cancer cells, the combination of AM with 4-OH-TMX showed a synergistic antiproliferative effect and favorable dose reduction. AM and 4-OH-TMX decreased KCNH1, CCND1, and BIRC5 gene expression. In endometrial cells, AM decreased MKI-67 gene expression, while it reverted the 4-OH-TMX-dependent CCND1 upregulation. This study establishes the benefits of incorporating AM as a co-adjuvant for first-line ER+ breast cancer therapy.

Three-dimensional cell cultures as preclinical models to assess the biological activity of phytochemicals in breast cancer

The demand for the development of three-dimensional (3D) cell culture models in both/either drug screening and/or toxicology is gradually magnified. Natural Products derived from plants are known as phytochemicals and serve as resources for novel drugs and cancer therapy. Typical examples include taxol analogs (i.e., paclitaxel and docetaxel), vinca alkaloids (i.e., vincristine, vinblastine), and camptothecin analogs (topotecan, irinotecan). Breast cancer is the most frequent malignancy in women, with a 70% chance of patients being cured; however, metastatic disease is not considered curable using currently available chemotherapeutic options. In addition, phytochemicals present promising options for overcoming chemotherapy-related problems, such as drug resistance and toxic effects on non-target tissues. In the toxicological evaluation of these natural compounds, 3D cell culture models are a powerful tool for studying their effects on different tissues and organs in similar environments and behave as if they are in vivo conditions. Considering that 3D cell cultures represent a valuable platform for identifying the biological features of tumor cells as well as for screening natural products with antitumoral activity, the present review aims to summarize the most common 3D cell culture methods, focusing on multicellular tumor spheroids (MCTS) of breast cancer cell lines used in the discovery of phytochemicals with anticancer properties in the last ten years.

Suppressive effect of α-mangostin for cancer stem cells in colorectal cancer via the Notch pathway

Background

Since colon cancer stem cells (CSCs) play an important role in chemoresistance and in tumor recurrence and metastasis, targeting of CSCs has emerged as a sophisticated strategy for cancer therapy. α-mangostin (αM) has been confirmed to have antiproliferative and apoptotic effects on cancer cells. This study aimed to evaluate the selective inhibition of αM on CSCs in colorectal cancer (CRC) and the suppressive effect on 5-fluorouracil (5-FU)-induced CSCs.

Methods

The cell viability assay was performed to determine the optimal concentration of αM. A sphere forming assay and flow cytometry with CSC markers were carried out to evaluate the αM-mediated inhibition of CSCs. Western blot analysis and quantitative real-time PCR were performed to investigate the effects of αM on the Notch signaling pathway and colon CSCs. The in vivo anticancer efficacy of αM in combination with 5-FU was investigated using a xenograft mouse model.

Results

αM inhibited the cell viability and reduced the number of spheres in HT29 and SW620 cells. αM treatment decreased CSCs and suppressed the 5-FU-induced an increase in CSCs on flow cytometry. αM markedly suppressed Notch1, NICD1, and Hes1 in the Notch signaling pathway in a time- and dose-dependent manner. Moreover, αM attenuated CSC markers CD44 and CD133, in a manner similar to that upon DAPT treatment, in HT29 cells. In xenograft mice, the tumor and CSC makers were suppressed in the αM group and in the αM group with 5-FU treatment.

Conclusion

This study shows that low-dose αM inhibits CSCs in CRC and suppresses 5-FU–induced augmentation of CSCs via the Notch signaling pathway.

Synthesis and Properties of α-Mangostin and Vadimezan Conjugates with Glucoheptoamidated and Biotinylated 3rd Generation Poly(amidoamine) Dendrimer, and Conjugation Effect on Their Anticancer and Anti-Nematode Activities

α-Mangostin and vadimezan are widely studied potential anticancer agents. Their biological activities may be improved by covalent bonding by amide or ester bonds with the third generation poly(amidoamine) (PAMAM) dendrimer, substituted with α-D-glucoheptono-1,4-lactone and biotin. Thus, conjugates of either ester- (G3^gh4B5V) or amide-linked (G3^2B12gh5V) vadimezan, and equivalents of α-mangostin (G3^gh2B5M and G3^2B12gh5M, respectively), were synthesized, characterized and tested in vitro against cancer cells: U-118 MG glioma, SCC-15 squamous carcinoma, and BJ normal human fibroblasts growth, as well as against C. elegans development. α-Mangostin cytotoxicity, stronger than that of Vadimezan, was increased (by 2.5–9-fold) by conjugation with the PAMAM dendrimer (with the amide-linking being slightly more effective), and the strongest effect was observed with SCC-15 cells. Similar enhancement of toxicity resulting from the drug conjugation was observed with C. elegans. Vadimezan (up to 200 µM), as well as both its dendrimer conjugates, was not toxic against both the studied cells and nematodes. It showed an antiproliferative effect against cancer cells at concentrations ≥100 µM. This effect was significantly enhanced after conjugation of the drug with the dendrimer via the amide, but not the ester bond, with G3^2B12gh5V inhibiting the proliferation of SCC-15 and U-118 MG cells at concentrations ≥4 and ≥12 μM, respectively, without a visible effect in normal BJ cells. Thus, the drug delivery system based on the PAMAM G3 dendrimer containing amide bonds, partially-blocked amino groups on the surface, larger particle diameter and higher zeta potential can be a useful tool to improve the biological properties of transported drug molecules.

α-Mangostin Induces Apoptosis and Inhibits Metastasis of Breast Cancer Cells via Regulating RXRα-AKT Signaling Pathway

Mangostin, which has the function of anti-inflammatory, antioxidant, and anticancer, etc, is one of the main active ingredients of the hull of the mangosteen. The main objective of the study was to elucidate its anti-cancer function and possible mechanism. α-Mangostin was separated and structurally confirmed. MTT method was used to check the effect of mangostin on breast cancer cell proliferation. Then the effect of α-Mangostin on the transcriptional activity of RXRα was tested by dual-luciferase reporter gene assay. And Western blot (WB) was used to detect the expression of apoptosis-related proteins or cell cycle-associated proteins after treatment. Also, this study was to observe the effects of α-Mangostin on the invasion of breast cancer cell line MDA-MB-231. α-Mangostin regulates the downstream effectors of the PI3K/AKT signaling pathway by degrading RXRα/tRXRα. α-Mangostin can trigger PARP cleavage and induce apoptosis, which may be related to the induction of upregulated BAX expression and downregulation of BAD and cleaved caspase-3 expression in MDA-MB-231 cells through blockade of AKT signaling. The experiments verify that α-Mangostin have evident inhibition effects of invasion and metastasis of MDA-MB-231 cells. Cyclin D1 was involved in the anticancer effects of α-Mangostin on the cell cycle in MDA-MB-231 cells. α-Mangostin induces apoptosis, suppresses the migration and invasion of breast cancer cells through the PI3K/AKT signaling pathway by targeting RXRα, and cyclin D1 has involved in this process.

Molecular Mechanism of Secondary Endocrine Resistance in Luminal Breast Cancer

OBJECTIVE

The molecular mechanism of secondary resistance in Luminal breast cancer was studied to provide new ideas for the treatment of breast cancer.

METHODS

The sensitivity of the downregulation of myeloid leukemia factor 1-interacting proteins (MLF1IP) to Tamoxifen (TAM) was tested by the Cell Counting Kit-8 (CCK-8). The apoptosis of MLF1IP-mediated resistance was analyzed by flow cytometry (FCM) with/without TAM. Western blot was used in detecting various kinds of apoptosis and the expression of the protein related to the phosphatidylinositol 3-kinase (PI3K)/AKT signaling pathway to study the molecular mechanism of secondary endocrine resistance in Luminal breast cancer.

RESULTS

The downregulation of MLF1IP could significantly increase the drug sensitivity of Michigan Cancer Foundation-7 (MCF-7) cells and also inhibit the proliferation of MCF-7 cells under the stimulation of drugs. Western blot results showed that the expression of Bcl-2-associated X (BAX), Caspase3, Caspase7, and Caspase9 proteins increased when MLF1IP was downregulated. The results of the PI3K/AKT signaling pathway revealed that the phosphatase and tensin homolog deleted on chromosome ten (PTEN) protein expression of MCF7-shRNA was higher than that of MCF7-NC cells, while the expression of p-AKT was lower than that of MCF7-NC cells.

CONCLUSIONS

(1) MLF1IP-related apoptosis resistance plays an essential role in MLF1IP-mediated secondary resistance of breast cancer cells. (2) MLF1IP promotes AKT phosphorylation by inhibiting the PTEN expression, thus activating the PI3K/AKT signaling pathway and causing the secondary resistance of Luminal breast cancer. (3) MLF1IP can be used as a factor to predict the endocrine resistance of Luminal breast cancer.

α-Mangostin Synergizes the Antineoplastic Effects of 5-Fluorouracil Allowing a Significant Dose Reduction in Breast Cancer Cells

Breast cancer is the most common neoplasm and the leading cause of cancer death in women worldwide. Although 5-fluorouracil is a conventional chemotherapeutic agent for breast cancer treatment, its use may result in severe side effects. Thus, there is widespread interest in lowering 5-fluorouracil drawbacks, without affecting its therapeutic efficacy by the concomitant use with natural products. Herein, we aimed at evaluating whether α-mangostin, a natural antineoplastic compound, could increase the anticancer effect of 5-fluorouracil in different breast cancer cell lines, allowing for dose reduction. Cell proliferation was evaluated by sulforhodamine-B assays, inhibitory concentrations and potency were calculated by dose-response curves, followed by analysis of their pharmacological interaction by the combination-index method and dose-reduction index. Cell cycle distribution was evaluated by flow cytometry. Each compound inhibited cell proliferation in a dose-dependent manner, the triple negative breast cancer cells being the most sensitive. When 5-fluorouracil and α-mangostin were used concomitantly, synergistic antiproliferative effect was observed. The calculated dose-reduction index suggested that this combination exhibits therapeutic potential for reducing 5-fluorouracil dosage in breast cancer. Mechanistically, the cotreatment induced cell death in a greater extent than each drug alone. Therefore, α-mangostin could be used as a potent co-adjuvant for 5-fluorouracil in breast cancer.