Adapalene Inhibits Prostate Cancer Cell Proliferation In Vitro and In Vivo by Inducing DNA Damage, S-phase Cell Cycle Arrest, and Apoptosis

Adapalene potentiates the cytotoxicity of anti-cancer drugs by enhancing cell cycle dysregulation and apoptosis in MKN-45 cells

Adapalene is a third-generation synthetic retinoid that has been approved by the FDA as a dermatological drug was recently repurposed for its potential anti-cancer effects. Here, its anti-cancer potential was determined in human gastric adenocarcinoma cell lines. Adapalene did not show significant cytotoxicity toward AGS and MKN-45 cells, but displayed synergistic or additive effects in inhibiting cell growth and increasing apoptosis in MKN-45 cells, but not AGS cells, when combined with 5-FU, cisplatin, docetaxel, or doxorubicin. Co-treatment with adapalene plus docetaxel or doxorubicin increased DNA damage and S-phase arrest without affecting the expression levels of HR23A/B, XPC, or Rad51. In MKN-45 cells exposed to docetaxel or doxorubicin, adapalene co-treatment downregulated Aurora A and upregulated p21, potentially contributing to its ability to enhance DNA damage and cell cycle dysregulation, and increased reactive oxygen species (ROS) accumulation, which may potentiate the cytotoxicity of the anti-cancer agents. Our present results reveal that adapalene is not cytotoxic towards MKN-45 gastric cancer cells when applied alone, but can synergistically enhance the sensitivity of these cells to conventional chemotherapeutic drugs. Further investigations are warranted to fully elucidate the mechanisms underlying the synergistic effects of adapalene and identify markers that could, given the heterogeneity of gastric cancers, identify patients who are likely to benefit from adapalene co-treatment.

Polyphyllin VI: A promising treatment for prostate cancer bone metastasis

Prostate cancer, as one of the most prevalent malignant tumors in men, seriously affects the prognosis and survival of patients due to its extremely high rate of bone metastasis. This study investigated the effect of Polyphyllin VI (PPVI) on metastatic bone disease for the first time in prostate cancer, focusing on its impact on osteoclast and tumor cell. In vitro studies utilized TRAP staining, ghost pen cyclic peptide staining, and bone resorption assays to evaluate the differentiation and function of receptor activator of nuclear factor-κB ligand (RANKL) induced and RM-1 conditional medium (CM) induced osteoclasts. The colony formation assay, wound healing assay, and Transwell assay were employed to analyze tumor cell proliferation, migration, and invasion in vitro. Flow cytometry was used to detect the cycling and apoptosis of tumor cells in vitro. Western Blot and PCR assays were conducted to assess the expression of genes. In vivo, micro-CT, hematoxylin-eosin staining, and immunohistochemical staining evaluated the impact of PPVI on bone destruction and tumor growth in a mouse model of tumor tibial metastasis. The study results indicated that PPVI effectively inhibited osteoclast differentiation, suppresses tumor cell proliferation, migration, and invasion in vitro, and induces apoptosis and G2/M phase arrest. In vivo, PPVI not only inhibits the growth of metastatic tumors but also mitigates the resulting bone destruction. These results suggest that PPVI holds significant potential as an alternative treatment for prostate cancer with bone metastasis, providing insights into its molecular mechanisms and therapeutic efficacy.

Multidimensional role of adapalene in regulating cell death in multiple myeloma

Aims

Multiple myeloma (MM) remains a challenging condition to cure, with persistent drug resistance negating the benefits of treatment advancements. The unraveling complexities in programmed cell death (PCD), inclusive of apoptosis, autophagy, and ferroptosis, have highlighted novel therapeutic avenues. Our study focuses on deciphering how adapalene (ADA), a small molecule compound, accelerates the demise of MM cells via targeting their compensatory survival mechanisms.

Methods

To assess the impact of ADA on MM, we employed flow cytometry and trypan blue exclusion assays to determine cell viabilities across MM cell lines and primary patient samples post-treatment. To delineate ADA's therapeutic targets and mechanisms, we conducted RNA sequencing (RNA-seq), gene set enrichment analysis (GSEA), molecular docking, and molecular dynamics simulations. We further designed pre-clinical trials emphasizing MM, exploring the efficacy of ADA as a standalone and in combination with bortezomib (BTZ).

Results

ADA elicited a dose-responsive induction of MM cell death. Building upon ADA's anti-MM capabilities as a single agent, we proposed that ADA-BTZ co-treatment might amplify this lethality. Indeed, ADA and BTZ together greatly potentiated MM cell death. ADA proved beneficial in restoring BTZ susceptibility in BTZ-resistant relapsed or refractory MM (RRMM) patient cells. Molecular simulations highlighted ADA's high affinity (-9.17 kcal/mol) for CD138, with MM-GBSA revealing a binding free energy of -27.39 kcal/mol. Detailed interaction analyses indicated hydrogen-bonding of ADA with CD138 at the Asp35 and Gln34 residues. Additionally, ADA emerged as a versatile instigator of both ferroptosis and apoptosis in MM cells. Furthermore, ADA disrupted activation of the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) pathway triggered by BTZ, fostering cell death in BTZ-resistant MM subsets.

Conclusion

ADA demonstrates a comprehensive capability to orchestrate MM cell death, exerting pronounced anti-MM activity while disrupting NF-κB-related drug resistance. ADA sensitization of MM cells to BTZ unravels its potential as a novel therapeutic drug for MM management.

Environmentally sensitive fluorescence of the topical retinoid adapalene

Intrinsic fluorescence of drugs brings valuable information on their localization in the organism and their interaction with key biomolecules. In this work, we investigate the absorption and emission properties of the topical retinoid adapalene in different solvents and biological media. While the UVA/UVB absorption band does not exhibit any significant solvent-dependent behavior, a strong positive solvatochromism is observed for the emission. These results are in line with molecular modeling and simulations that show the presence of two quasi-degenerate states, i.e., a local π-π* and an intermolecular charge-transfer (ICT) state. However, molecular modeling also revealed that, whatever the solvent, at the corresponding equilibrium geometry the lowest and emissive excited state is the local π-π*. Finally, the potential of adapalene to act as a biological probe is demonstrated using albumin, DNA and micelles.

Targeting SMAD-Dependent Signaling: Considerations in Epithelial and Mesenchymal Solid Tumors

SMADs are the canonical intracellular effector proteins of the TGF-β (transforming growth factor-β). SMADs translocate from plasma membrane receptors to the nucleus regulated by many SMAD-interacting proteins through phosphorylation and other post-translational modifications that govern their nucleocytoplasmic shuttling and subsequent transcriptional activity. The signaling pathway of TGF-β/SMAD exhibits both tumor-suppressing and tumor-promoting phenotypes in epithelial-derived solid tumors. Collectively, the pleiotropic nature of TGF-β/SMAD signaling presents significant challenges for the development of effective cancer therapies. Here, we review preclinical studies that evaluate the efficacy of inhibitors targeting major SMAD-regulating and/or -interacting proteins, particularly enzymes that may play important roles in epithelial or mesenchymal compartments within solid tumors.

In Silico, In Vitro, and In Vivo Investigations on Adapalene as Repurposed Third Generation Retinoid against Multiple Myeloma and Leukemia

The majority of hematopoietic cancers in adults are incurable and exhibit unpredictable remitting-relapsing patterns in response to various therapies. The proto-oncogene c-MYC has been associated with tumorigenesis, especially in hematological neoplasms. Therefore, targeting c-MYC is crucial to find effective, novel treatments for blood malignancies. To date, there are no clinically approved c-MYC inhibitors. In this study, we virtually screened 1578 Food and Drug Administration (FDA)-approved drugs from the ZINC15 database against c-MYC. The top 117 compounds from PyRx-based screening with the best binding affinities to c-MYC were subjected to molecular docking studies with AutoDock 4.2.6. Retinoids consist of synthetic and natural vitamin A derivatives. All-trans-retinoic acid (ATRA) were highly effective in hematological malignancies. In this study, adapalene, a third-generation retinoid usually used to treat acne vulgaris, was selected as a potent c-MYC inhibitor as it robustly bound to c-MYC with a lowest binding energy (LBE) of -7.27 kcal/mol, a predicted inhibition constant (pKi) of 4.69 µM, and a dissociation constant (Kd value) of 3.05 µM. Thus, we examined its impact on multiple myeloma (MM) cells in vitro and evaluated its efficiency in vivo using a xenograft tumor zebrafish model. We demonstrated that adapalene exerted substantial cytotoxicity against a panel of nine MM and two leukemic cell lines, with AMO1 cells being the most susceptible one (IC50 = 1.76 ± 0.39 µM) and, hence, the focus of this work. Adapalene (0.5 × IC50, 1 × IC50, 2 × IC50) decreased c-MYC expression and transcriptional activity in AMO1 cells in a dose-dependent manner. An examination of the cell cycle revealed that adapalene halted the cells in the G2/M phase and increased the portion of cells in the sub-G0/G1 phase after 48 and 72 h, indicating that cells failed to initiate mitosis, and consequently, cell death was triggered. Adapalene also increased the number of p-H3(Ser10) positive AMO1 cells, which is a further proof of its ability to prevent mitotic exit. Confocal imaging demonstrated that adapalene destroyed the tubulin network of U2OS cells stably transfected with a cDNA coding for α-tubulin-GFP, refraining the migration of malignant cells. Furthermore, adapalene induced DNA damage in AMO1 cells. It also induced apoptosis and autophagy, as demonstrated by flow cytometry and western blotting. Finally, adapalene impeded tumor growth in a xenograft tumor zebrafish model. In summary, the discovery of the vitamin A derivative adapalene as a c-MYC inhibitor reveals its potential as an avant-garde treatment for MM.

Identification of Promising Drug Candidates against Prostate Cancer through Computationally-Driven Drug Repurposing

Prostate cancer (PC) is one of the most common types of cancer in males. Although early stages of PC are generally associated with favorable outcomes, advanced phases of the disease present a significantly poorer prognosis. Moreover, currently available therapeutic options for the treatment of PC are still limited, being mainly focused on androgen deprivation therapies and being characterized by low efficacy in patients. As a consequence, there is a pressing need to identify alternative and more effective therapeutics. In this study, we performed large-scale 2D and 3D similarity analyses between compounds reported in the DrugBank database and ChEMBL molecules with reported anti-proliferative activity on various PC cell lines. The analyses included also the identification of biological targets of ligands with potent activity on PC cells, as well as investigations on the activity annotations and clinical data associated with the more relevant compounds emerging from the ligand-based similarity results. The results led to the prioritization of a set of drugs and/or clinically tested candidates potentially useful in drug repurposing against PC.

Adapalene inhibits the growth of triple-negative breast cancer cells by S-phase arrest and potentiates the antitumor efficacy of GDC-0941

Although advances in diagnostics and therapeutics have prolonged the survival of triple-negative breast cancer (TNBC) patients, metastasis, therapeutic resistance, and lack of targeted therapies remain the foremost hurdle in the effective management of TNBC. Thus, evaluation of new therapeutic agents and their efficacy in combination therapy is urgently needed. The third-generation retinoid adapalene (ADA) has potent antitumor activity, and using ADA in combination with existing therapeutic regimens may improve the effectiveness and minimize the toxicities and drug resistance. The current study aimed to assess the anticancer efficacy of adapalene as a combination regimen with the PI3K inhibitor (GDC-0941) in TNBC in vitro models. The Chou–Talalay’s method evaluated the pharmacodynamic interactions (synergism, antagonism, or additivity) of binary drug combinations. Flow cytometry, Western blotting, and in silico studies were used to analyze the mechanism of GDC–ADA synergistic interactions in TNBC cells. The combination of GDC and ADA demonstrated a synergistic effect in inhibiting proliferation, migration, and colony formation of tumor cells. Accumulation of reactive oxygen species upon co-treatment with GDC and ADA promoted apoptosis and enhanced sensitivity to GDC in TNBC cells. The findings indicate that ADA is a promising therapeutic agent in treating advanced BC tumors and enhance sensitivity to GDC in inhibiting tumor growth in TNBC models while reducing therapeutic resistance.

MY11 exerts antitumor effects through activation of the NF-κB/PUMA signaling pathway in breast cancer

Breast cancer is the most common malignancy in women worldwide, and the discovery of new effective breast cancer therapies with lower toxicity is still needed. We screened a series of chalcone derivatives and found that MY11 ((E)-1-(2-hydroxy-4,6-dimethoxyphenyl)-3-(4-piperazinylphenyl) prop-2-en-1-one) had the strongest anti-breast cancer activity. MY11 inhibited the growth of MDA-MB-231 and MCF-7 breast cancer cells by arresting the cell cycle and promoting apoptosis, through regulation of the cell cycle and apoptosis-related proteins. PDTC (Pyrrolidinedithiocarbamate ammonium), a specific inhibitor of the NF-κB pathway, abolished the inhibitory effect of MY11 treatment. NF-κB has been shown to regulate PUMA-dependent apoptosis. Our in vitro studies demonstrated that MY11 promoted breast cancer cell apoptosis by activating the NF-κB/PUMA/mitochondrial apoptosis pathway (including Bcl-2, Bax, and Caspase-9). MY11 also inhibited tumor growth in an orthotopic breast cancer mouse model by inducing apoptosis through the NF-κB signaling pathway, importantly, with minimal toxicity. In addition, MY11 was found by docking analysis to bind to p65, which might enhance the stability of the p65 protein. Taken together, our findings indicate that MY11 exerts a significant anticancer effect in breast cancer and that it may be a potential candidate for the treatment of breast cancer.