Many purified compounds from dietary sources have been investigated for their anticancer activities. The main issue with most agents is their effectiveness at high doses which generally could not be delivered to humans through dietary consumption. Here, we observed that cucurbitacin B, a tetracyclic triterpenoid present in pumpkins, gourds and squashes, exhibits antiproliferative effects on human non-small cell lung cancer (NSCLC) cells at nanomolar concentrations. Treatment with cucurbitacin B (0.2-0.6 μM; 24 h) was found to result in decrease in the viability of EGFR-wild type (A549 and H1792) and EGFR-mutant lung cancer cells (H1650 and H1975) and reduction in cell-colonies but had only minimal effect on normal human bronchial epithelial cells. Treatment with cucurbitacin B also caused inhibition of PI3K/mTOR and signal transducer and activator of transcription (STAT)-3 signaling along with simultaneous activation of AMPKα levels in both EGFR-wild type and EGFR-mutant lung cancer cells. Cucurbitacin B caused specific increase in the protein and mRNA expression of sestrin-3 in EGFR-mutant lung cancer cells, but not in EGFR-wild type cells. Treatment with cucurbitacin B to sestrin-3 siRNA treated EGFR-mutant cells further amplified the decrease in cell-viability and caused more sustained G2-phase cell cycle arrest, suggesting that these effects are mediated partly through sestrin-3. We also found that sestrin-3 has a role in the induction of apoptosis by cucurbitacin B in both EGFR-wild type and EGFR-mutant lung cancer cells. These findings suggest novel mechanism by the modulation of sestrin-3 for the action of cucurbitacin B and suggest that it could be developed as an agent for therapy of NSCLC.
The normal colon epithelium is transformed into its neoplastic counterpart through a series of genetic alterations in driver genes including activating mutations in PIK3CA. Treatment often involves surgery followed by 5-fluorouracil (5-FU) based therapy, which has limited efficiency and serious side effects. We sought to determine whether fisetin, a dietary flavonoid, alone or in combination with 5-FU affected tumorigenesis in the mammalian intestine. We first determined the effect of fisetin, 5-FU or their combination on PIK3CA-mutant and PIK3CA wild-type colon cancer cells by assessing cell viability, colony formation, apoptosis and effects on PI3K/AKT/mTOR signaling. Treatment of PIK3CA-mutant cells with fisetin and 5-FU reduced the expression of PI3K, phosphorylation of AKT, mTOR, its target proteins, constituents of mTOR signaling complex and this treatment increased the phosphorylation of AMPKα. We then determined whether fisetin and 5-FU together or singly affected tumorigenesis in Apc Min/+ mice that also express constitutively active PI3K in the distal small intestine and colon. Tumor incidence was markedly lower in fisetin-treated FC 1 3K 1 Apc Min/+ mice that also express constitutively active PI3K in distal small intestine and colon, as compared to control animals, indicating that fisetin is a strong preventive agent. In addition, the combination of fisetin and 5-FU also reduced the total number of intestinal tumors. Fisetin could be used as a preventive agent plus an adjuvant with 5-FU for the treatment of PIK3CA-mutant colorectal cancer.
Colorectal cancer (CRC) is one of the most frequent and deadliest cancers worldwide with patients often diagnosed in advanced stages of the disease. Approximately 15-20% of advanced colorectal cancers harbor activating mutations in PIK3CA, which has been identified as an important oncogene in multiple cancers. Therefore, modeling the effects of this type of mutation in the mammalian colon is significant. Fisetin is a naturally occurring flavonoid in strawberry, apple, persimmon, grape, onion and cucumber. 5-Fluorouracil (5-FU) is the most used chemotherapeutic agent in CRC; however, it has serious side-effects. Therefore, augmentation of the 5-FU therapeutic effect could lead to lower effective doses and subsequently fewer side effects. We conducted in-vitro and in-vivo studies to determine the effect of fisetin, 5-FU and their combination on PI3K/AKT/mTOR signaling in PIK3CA-mutant colon cancer cells (HCT116 and HT-29), PIK3CA wild-type colon cancer cells (SW480), and newly developed mouse models. We found that there was more pronounced decrease in cell-viability and number of colonies in PIK3CA-mutant colon cancer cells than PIK3CA wild-type colon cancer cells. Apoptotic genes and proteins are promising targets for cancer treatment as they provide several theoretical basis to influence pathways causing greater tumor cell death. We observed an increase in the protein expression of Bax and decrease in Bcl2 on treatment with combination of fisetin and 5-FU than either agent alone. The full size PARP (116 KD) protein was also cleaved to yield an 85 KD fragment after treatment of cells with fisetin, 5-FU and their combination. Apoptotic effects of fisetin and 5-FU combination were also confirmed by flow cytometry in PIK3CA-mutant colon cancer cells. The PI3K/AKT pathway is frequently activated in CRC leading to tumorigenesis and the resistance to chemotherapy. Treatment of PIK3CA-mutant colon cancer cells with fisetin and 5-FU caused decrease in the expression of (i) PI3K (p85 and p110), (ii) phosphorylation of Akt (Ser473 and Thr308), (iii), phosphorylation of mTOR, its target proteins, and constituents of mTOR signaling complex. Treatment with fisetin and 5-FU also led to an increase in the phosphorylation of AMPKα. Next, we performed studies to investigate the effect of the treatment of combination of fisetin and 5-FU on colorectal tumorigenesis in FC13K1ApcMin/+ mice. These animals form tumors in the distal small intestine and colon that have lost APC activity and express constitutively active PI3K as often occurs in humans. Interestingly, the effect of fisetin was much stronger than that of 5-FU and comparable to the fisetin and 5-FU combination. Both fisetin only and combination treatment groups had significantly lower incidence relative to the control group. We suggest that fisetin could be used as a preventive agent as well as an adjuvant with 5-FU for the treatment of PIK3CA-mutant CRC. Citation Format: Naghma Khan, Farah Jajeh, Devon Miller, Rachel Van Doorn, Richard B. Halberg, Hasan Mukhtar. Fisetin, a dietary flavonoid for the prevention and treatment of PIK3CA-mutant colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2030. doi:10.1158/1538-7445.AM2017-2030
Lung cancer is the primary cause of cancer death in both men and women in the United States and worldwide. The general prognosis is still very low despite of developments in the treatment due to improved surgical techniques, increased application of combined modality treatments and the use of new drugs. Since the past decade, researchers have been investigating a range of purified compounds from dietary sources as possible anticancer drugs. The main issue with the use of natural products is their effectiveness at high doses which generally could not be delivered to humans through dietary consumption. Here, we observed that cucurbitacin B exhibits antiproliferative effects on human non-small cell lung cancer (NSCLC) cells at very low concentrations. The cucurbitacins are highly diverse and oxygenated tetracyclic triterpenoids isolated from plants of Cucurbitaceae family which are well-known for their bitterness of edible products like pumpkins, gourds and squashes. Cucurbitacin B is one of the most abundant and has been most widely used. In this study, we determined the effect of cucurbitacin B on the inhibition of cell-growth and suppression of phosphatidylinositol 3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) signaling in human NSCLC cells. Treatment of cucurbitacin B (0.2-0.6 μM; 24 h) was found to result in 34-61% and 45-65% decrease in the viability of human NSCLC H1792 and A549 cells respectively, but had only minimal effect on normal human bronchial epithelial cells. The IC50 of cucurbitacin B in these cells ranged from 0.43-0.49 μM. The A549 cell colonies were also reduced by treatment with cucurbitacin B in a dose-dependent manner. It has been well documented that mTOR functions downstream of the PI3K/Akt pathway and is phosphorylated in response to stimuli that activate the PI3K/Akt pathway. Treatment of A549 cells with cucurbitacin B (0.2-0.6 μM; 24 h) caused decrease in the protein expression of PI3K (p85 and p110) and inhibition of the phosphorylation of Akt and mTOR. PI3K/Akt-dependent phosphorylation signals through tuberin, the protein product of tuberous sclerosis complex (TSC)1/TSC2 complex, which leads to activation of mTOR. The mTOR also phosphorylates eukaryotic translation initiation factor 4E-binding protein 1 (4E-BP1) which disassociates from the eukaryotic translation initiation factor (eIF) 4E, allowing activation of protein translation. Treatment of A549 cells with cucurbitacin B also caused inhibition of the phosphorylation of p70S6K1, eIF-4E and 4E-BP1 and downstream targets of mTOR. In cucurbitacin B treated cells, there was also inhibition of the constituents of mTOR signaling complex such as Rictor, Raptor, GβL and PRAS40 and activation of AMP-activated protein kinase (AMPKα) and tuberous sclerosis complex (TSC)2. We suggest that cucurbitacin B could be developed as an agent for the management of lung cancer. Citation Format: Naghma Khan, Farah Jajeh, Sameh M. Shabana, Hasan Mukhtar. Cucurbitacin B: A novel natural agent for the management of non-small cell lung cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4109. doi:10.1158/1538-7445.AM2014-4109
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.