Carnosol, a Dietary Diterpene, Displays Growth Inhibitory Effects in Human Prostate Cancer PC3 Cells Leading to G2-Phase Cell Cycle Arrest and Targets the 5′-AMP-Activated Protein Kinase (AMPK) Pathway

Abstract

Purpose-The anti-cancer effect of carnosol was investigated in human prostate cancer PC3 cells.Methods-Biochemical analysis and protein array data of carnosol treated PC3 cells were analyzed.Results-We evaluated carnosol for its potential anti-cancer properties in the PC3 cells. Using an MTT assay we found that carnosol (10 -70 µM) decreases cell viability in a time and dose dependent manner. Next, we evaluated the effect of carnosol (20-60 uM) effect using flow cytometry as well as biochemical analysis and found induction of G2-phase cell cycle arrest. To establish a more precise mechanism, we performed a protein array that evaluated 638 proteins involved in cell signaling pathways. The protein array identified 5'-AMP-activated protein kinase (AMPK), a serine/threonine protein kinase involved in the regulation of cellular energy balance as a potential target. Further downstream effects consistent with cancer inhibition included the modulation of the mTOR/HSP70S6k/4E-BP1 pathway. Additionally, we found that carnosol targeted the PI3K/Akt pathway in a dose dependent manner.Conclusions-These results suggest that carnosol targets multiple signaling pathways that include the AMPK pathway. The ability of carnosol to inhibit prostate cancer in vitro suggests carnosol may be a novel agent for the management of PCa.

Natural Polyphenols that Display Anticancer Properties through Inhibition of Kinase Activity

“…This anticancer effect was associated with activation of AMPK-and inhibition of PI3K/Akt pathways [87]. This natural product also inhibited the invasion of B16F10 mouse melanoma cells through down-regulating cJun and inhibition of ERK1/2, Akt, p38, JNK kinases [92].…”

“…Carnosol (43) and carnosic acid (44) are two polyphenols of this group that are of relevance to kinase targeting and they were isolated from culinary herbs that include rosemary, sage and oregano (Table 4) [87].…”

“…Carnosol (43) displayed growth inhibitory effects in human prostate cancer PC3 cells [87]. This anticancer effect was associated with activation of AMPK-and inhibition of PI3K/Akt pathways [87].…”

Chemopreventive Activity of Mediterranean Medicinal Plants

“…Also, carnosol induces G2/M cell cycle arrest that targets cyclin A and cyclin B1 with an IC50 of 23 μM in Caco-2 colon adenocarcinoma cells which are representative of precancerous lesions (Visanji et al, 2006). Additional in vitro work has shown that carnosol significantly inhibited the highly metastatic mouse melanoma B16 cells through down regulation of matrix metalloproteinase 2, c-jun, as well as the redox sensitive transcription factor nuclear factor-kappa B (Nf-κB) (J.J. Johnson et al, 2008). Also, J.J. Johnson et al (2008) shows that carnosol promoted G2 cell cycle arrest of PC3 cell line, with inhibition of cyclins A, D1, D2 and cdks 2 and 6, and targets multiple signaling pathways that include the AMPK and PI3K/Akt pathway.…”

“…Additional in vitro work has shown that carnosol significantly inhibited the highly metastatic mouse melanoma B16 cells through down regulation of matrix metalloproteinase 2, c-jun, as well as the redox sensitive transcription factor nuclear factor-kappa B (Nf-κB) (J.J. Johnson et al, 2008). Also, J.J. Johnson et al (2008) shows that carnosol promoted G2 cell cycle arrest of PC3 cell line, with inhibition of cyclins A, D1, D2 and cdks 2 and 6, and targets multiple signaling pathways that include the AMPK and PI3K/Akt pathway. Resveratrol and chrysin can inhibit the proliferation of Caco-2 cells after 72h incubation when administered in combination at concentrations of 20 mM and 32 mM, respectively (Iwuchukwu et al, 2011).…”