Background/Objectives: Colorectal cancer (CRC) is the third most common cancer in the US and the second leading cancer-associated mortality cause. Available CRC therapies achieve modest outcomes and fail to prevent its recurrence. Epidemiological studies indicated that the Mediterranean diet rich in olive oil reduced CRC incidence. This study aimed at the identification and assessment of active anti-CRC olive phenolics. Methods: The MTT, wound-healing and colony formation assays were used to discover and assess the in vitro anti-CRC activity of olive phenolics. A nude mouse xenografting model was used to assess the in vivo CRC progression and recurrence suppressive activity of OC in pure and crude forms. OC was isolated from olive oil using liquid–liquid extractions. Results: Screening of olive phenolics for in vitro antiproliferative activity against a diverse panel of CRC cell lines identified the extra-virgin olive oil (EVOO) S-(-)-oleocanthal (OC) as the most active hit. OC showed IC₅₀ values of 4.2, 9.8, 14.5, and 4.9 μM against HCT-116, COLO-320DM, WiDr, and SW48 CRC cells, respectively. The lysine methyltransferases SMYD2 and EZH2, along with the receptor tyrosine kinase c-MET proved aberrantly dysregulated in invasive and metastatic CRC. SMYD2 and c-MET were validated as OC molecular targets in multiple malignancies. Daily oral 10 mg/kg OC treatments over 15 days suppressed 72.5% of the KRAS mutant HCT-116-Luc cells tumors weight in male nude mice. Continued OC daily oral use after primary tumor surgical excision over an additional 40 days significantly suppressed the HCT-116-Luc locoregional tumor recurrence and totally prevented the distant tumor recurrence. The SMYD2-EZH2 expressions and c-MET activation were notably suppressed by OC treatments in vitro and in collected animal primary tumors. Conclusions: OC and olive phenolics are potential nutraceutical interventions useful for CRC control and the prevention of its relapse.

Background/Objectives: Prostate cancer (PC) is among the most common malignancy in men. Several newly diagnosed patients have a locally advanced disease and distant metastasis at the initial diagnosis time. Castration-resistant PC (CRPC) patients have 100% recurrence incidence despite completing a therapeutic regimen, leading to high mortality. Androgen deprivation therapy and androgen inhibitors are initially effective, but resistance is inevitably developed. Epidemiological studies indicated that the Mediterranean diet, with high olive phenolic contents, is associated with a lower incidence of certain malignancies. This study aims at exploring the mCRPC progression and recurrence-suppressive and molecular effects of the major olive leaf phenolic glucoside (−)-oleuropein (OLE). Results: OLE downregulated the levels of proprotein convertase subtlisin/klexin type 9 (PCSK9) and normalized the low-density lipoprotein receptor (LDLR) in PC cells in vitro. Thus, a PCSK9-LDLR protein–protein interaction (PPI) in silico model was generated and used to assess OLE and its aglycone (OA) ability to bind at PCSK9 and thereby interfere with PCSK9-LDLR PPI. OLE perfectly filled the PCSK9 interface versus OA. Both OLE and OA showed virtual potential to interfere with PCSK9-LDLR PPI. OLE showed modest in vitro viability, migration, and clonogenicity suppressive effects on diverse human PC cell lines. OLE effectively suppressed mCRPC progression and recurrence in a nude mouse xenograft model. RNA-sequencing results proved the PCSK1, PCSK2, and PCSK9 downregulation in OLE-treated recurrent tumors versus vehicle control. Conclusions: Oleuropein is a novel lead useful for the control of mCRPC progression and the prevention of its recurrence via targeting PCSK9 expression and PPI with LDLR.

Background/Objectives. Prostate cancer (PCa) is the second leading cause of cancer-related mortality among men in the United States. Treatment with second-generation androgen receptor (AR) inhibitors, such as enzalutamide, can trigger lineage plasticity, promoting the transdifferentiation of PCa cells into an AR-independent, poorly differentiated neuroendocrine phenotype (NEPC). The receptor tyrosine kinase EPHA3 is a critical driver for NEPC. It is overexpressed in PCa, particularly in androgen-independent and neuroendocrine subtypes. EPHA3 activates c-Myc signaling to enhance EZH2 expression, promoting histone H3K27 trimethylation. The neural transcription factor BRN2 functions upstream of both EZH2 and ASCL1. The latter regulates the Notch pathway ligand DLL3, thereby orchestrating neuroendocrine differentiation. Elevated expression of classical neuroendocrine markers CHGA and SYP is characteristic of the NEPC phenotype. This study reports the novel usage of the olive phenolic S-(-)-hydroxyoleocanthal (HOC, oleacein) to effectively control NEPC by targeting the EPHA3–BRN2–EZH2–ASCL1–DLL3–SYP–CHGA oncogenic network. Methods. Cell viability assays were conducted to assess in vitro effects. To model NEPC progression and recurrence, NCI-H660-Luc cells were xenografted into male athymic nude mice. RNA-sequencing was performed to compare the differentially expressed genes between placebo control and treated tumors. Results. HOC significantly attenuated the proliferation of NEPC NCI-H660 cells in vitro. Daily oral administration of HOC at 10 mg/kg body weight markedly suppressed the progression of NEPC NCI-H660-Luc tumors. Continued HOC treatments after surgical excision of the primary tumors substantially reduced locoregional recurrence. HOC significantly downregulated the expression of EPHA3, BRN2, EZH2, ASCL1, DLL3, SYP, and CHGA in treated primary and recurrence tumors versus placebo control. Conclusions. These findings establish HOC as a multifaceted therapeutic entity capable of disrupting key NEPC oncogenic networks, highlighting its potential as a novel lead intervention for aggressive NEPC.

Background/Objectives. Prostate cancer (PCa) is among the leading causes of death from cancer in men. Frequent use of androgen receptor inhibitors induces PCa transdifferentiation, leading to poorly differentiated neuroendocrine PCa (NEPC). ROR2 is critical for NEPC pathogenesis by activating ASCL1, promoting lineage plasticity. Protein lysine methylation mediated by N-lysine methyltransferases SMYD2 and its downstream effector EZH2 upregulates the NEPC marker ASCL1 and enhances c-MET signaling, promoting PCa aggression. Epidemiological studies suggest a lower incidence of certain malignancies in Mediterranean populations due to their intake of an olive-phenolics-rich diet. Methods. Cell viability, gene knockdown, and immunoblotting were used for in vitro analyses. A nude mouse NEPC xenograft model evaluated the anti-tumor efficacy of purified and crude oleocanthal. Xenograft tumors were subjected to RNA-seq, qPCR, and Western blot analyses, with clinical validation performed using tissue microarrays. Results. A tissue microarray analysis showed that SMYD2 expression was significantly elevated in PCa tissues with higher IHS versus normal prostate tissue cores. The olive phenolic S–(–)–oleocanthal (OC) suppressed the de novo NEPC NCI-H660 cells proliferation. Male athymic nude mice xenografted with the NCI-H660-Luc cells were used to assess OC effects on de novo NEPC progression and recurrence. Male NSG mice transplanted with LuCaP 93 PDX tumor tissues generated a heterogeneous in vivo model used to assess OC effects against t-NEPC progression. Daily oral 10 mg/kg OC administration significantly suppressed the NCI-H660-Luc tumor progression and locoregional recurrence after primary tumor surgical excision. OC treatments effectively suppressed the progression of LuCaP 93 PDX tumors. OC-treated tumors revealed downregulation of ROR2, ASCL1, SMYD2, and EZH2, as well as activated c-MET levels versus the placebo control. RNA sequencing of the collected treated NEPC tumors showed that OC disrupted NEPC splicing, translation, growth factor signaling, and neuronal differentiation. Conclusions. This study’s findings validate OC as a novel lead entity for NEPC management by targeting the ROR2-ASCL1-SMYD2-EZH2-c-MET axis.

Background/Objectives: Colorectal cancer (CRC) is the second most common cancer-causing death in the United States. The Mediterranean diet, rich in extra-virgin olive oil (EVOO), is associated with a lower risk of colorectal cancer (CRC). Earlier studies reported S-(−)-oleocanthal (OC), the major EVOO phenolic, to be effective in CRC progression and recurrence suppression in a subcutaneous xenograft model by targeting the SMYD2–EZH2/c-MET signaling axis and favorably modulating gut microbiota (GM). However, lead validation in an orthotopically xenografted model that mimics the tumor microenvironment is yet to be achieved. The GM contribution to OC anti-CRC activity remains unknown. Methods: We used an orthotopic intra-cecally xenografted nude mouse model to validate OC anti-KRAS-mutant CRC activity and assessed the contribution of OC GM modulation to this activity using an oral antibiotic depletion strategy. Results: Daily oral 10 mg/kg OC impressively suppressed KRAS^G13D-mutant CRC HCT-116-Luc progression and metastasis more effectively than intraperitoneal administration 3×/week. By contrast, GM depletion with a broad-spectrum antibiotics cocktail (ABC) partially attenuated this activity, suggesting GM contribution to OC anti-CRC activity. Thus, fecal microbiota transplantation (FMT) was conducted using fresh daily oral fecal GM treatments collected from 20 mg/kg OC-dosed nude mouse donors. A week before FMT dosing, orthotopic HCT-116-Luc tumor-bearing recipient mice were subjected to GM depletion using daily oral ABC dosing. Recipient mice treated with FMT from OC-treated donors exhibited dramatic >99% reductions in primary and near-complete suppression of multi-organ metastatic tumor burden versus FMT controls. Conclusions: Collectively, oral OC is validated as an effective anti-KRAS^G13D-mutant CRC lead. Future clinical trials can validate its anti-CRC potential in a human model.