Ethan Walker

Diosmetin, a plant flavonoid, has been shown to exert promising effects on prostate cancer cells as an anti‑proliferative and anticancer agent. In this study, using western blot analysis for protein expression and flow cytometry for cell cycle analysis, we determined that the treatment of the LNCaP and PC‑3 prostate cancer cells with diosmetin resulted in a marked decrease in cyclin D1, Cdk2 and Cdk4 expression levels (these proteins remain active in the G0‑G1 phases of the cell cycle). These changes were accompanied by a decrease in c-Myc and Bcl-2 expression, and by an increase in Bax, p27Kip1 and FOXO3a protein expression, which suggests the potential modulatory effects of diosmetin on protein transcription. The treatment of prostate cancer cells with diosmetin set in motion an apoptotic machinery by inhibiting X-linked inhibitor of apoptosis (XIAP) and increasing cleaved PARP and cleaved caspase-3 expression levels. On the whole, the findings of this study provide an in-depth analysis of the molecular mechanisms responsible for the regulatory effects of diosmetin on key molecules that perturb the cell cycle to inhibit cell growth, and suggest that diosmetin may prove to be an effective anticancer agent for use in the treatment of prostate cancer in the future.

Metastatic castration-resistant prostate cancer poses a serious clinical problem with poor outcomes and remains a deadly disease. New targeted treatment options are urgently needed. PSMA is highly expressed in prostate cancer and has been an attractive biomarker for the treatment of prostate cancer. In this study, we explored the feasibility of targeted delivery of an antimitotic drug, monomethyl auristatin E (MMAE), to tumor tissue using a small-molecule based PSMA lig-and. With the aid of Cy5.5, we found that a cleavable linker is vital for the antitumor activity of the ligand-drug conjugate and have developed a new PSMA-targeting prodrug, PSMA-1-VcMMAE. In in vitro studies, PSMA-1-VcMMAE was 48-fold more potent in killing PSMA-positive PC3pip cells than killing PSMA-negative PC3flu cells. In in vivo studies, PSMA-1-VcMMAE significantly inhibited tumor growth leading to prolonged animal survival in different animal models, including metastatic prostate cancer models. Compared to anti-PSMA antibody-MMAE conjugate (PSMA-ADC) and MMAE, PSMA-1-VcMMAE had over a 10-fold improved maximum tolerated dose, resulting in improved therapeutic index. The small molecule-drug conjugates reported here can be easily synthesized and are more cost efficient than anti-body-drug conjugates. The therapeutic profile of the PSMA-1-VcMMAE encourages further clin-ical development for the treatment of advanced prostate cancer.

The majority of breast cancer patients is treated with breast-conserving surgery (BCS) combined with adjuvant radiation therapy. Up to 40% of patients has a tumor-positive resection margin after BCS, which necessitates re-resection or additional boost radiation. Cathepsin-targeted near-infrared fluorescence imaging during BCS could be used to detect residual cancer in the surgical cavity and guide additional resection, thereby preventing tumor-positive resection margins and associated mutilating treatments. The cysteine cathepsins are a family of proteases that play a major role in normal cellular physiology and neoplastic transformation. In breast cancer, the increased enzymatic activity and aberrant localization of many of the cysteine cathepsins drive tumor progression, proliferation, invasion, and metastasis. The upregulation of cysteine cathepsins in breast cancer cells indicates their potential as a target for intraoperative fluorescence imaging. This review provides a summary of the current knowledge on the role and expression of the most important cysteine cathepsins in breast cancer to better understand their potential as a target for fluorescence-guided surgery (FGS). In addition, it gives an overview of the cathepsin-targeted fluorescent probes that have been investigated preclinically and in breast cancer patients. The current review underscores that cysteine cathepsins are highly suitable molecular targets for FGS because of favorable expression and activity patterns in virtually all breast cancer subtypes. This is confirmed by cathepsin-targeted fluorescent probes that have been shown to facilitate in vivo breast cancer visualization and tumor resection in mouse models and breast cancer patients. These findings indicate that cathepsin-targeted FGS has potential to improve treatment outcomes in breast cancer patients.