PMID: 

Strahlenther Onkol. 2010 Mar ;186(3):143-8. Epub 2010 Feb 22. PMID: 20339825

Abstract Title: 

Betulinic acid a radiosensitizer in head and neck squamous cell carcinoma cell lines.

Abstract: 

BACKGROUND AND PURPOSE: Betulinic acid, a pentacyclic triterpene, is a new cytotoxic compound active on melanoma, neuroblastoma, glioblastoma and head and neck squamous cell carcinoma (HNSCC) cells. In combination with irradiation it has been shown to have an additive effect on growth inhibition in melanoma cells. In this study, the radiosensitizing effect of betulinic acid on sequential irradiation was investigated in HNSCC cell lines.MATERIAL AND METHODS: Two HNSCC cell lines, SCC9 and SCC25, were treated with increasing doses of betulinic acid and sequentially irradiated with a single boost of 4 Gy from a conventional radiation source. The cells were counted, the surviving fraction was determined, and colony-forming assays were performed.RESULTS: It could be shown that betulinic acid alone inhibits cell survival, affects cell survival additively in combination with irradiation and decreases clonogenic survival in both cell lines when applied alone.CONCLUSION: Betulinic acid could be a promising treatment agent in radioresistant head and neck cancer. A combination of betulinic acid with radiotherapy seems to be beneficial.

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PMID: 

Int J Cancer. 2010 Jul 15 ;127(2):282-92. PMID: 19937797

Abstract Title: 

Betulinic acid suppresses STAT3 activation pathway through induction of protein tyrosine phosphatase SHP-1 in human multiple myeloma cells.

Abstract: 

STAT3 activation has been associated with survival, proliferation and invasion of various human cancers. Whether betulinic acid, a pentacyclic triterpene, can modulate the STAT3 pathway, was investigated in human multiple myeloma (MM) cells. We found that betulinic acid inhibited constitutive activation of STAT3, Src kinase, JAK1 and JAK2. Pervanadate reversed the betulinic acid-induced downregulation of STAT3 activation, suggesting the involvement of a protein tyrosine phosphatase (PTP). Furthermore, betulinic acid induced the expression of the PTP SHP-1 and silencing of the SHP-1 gene abolished the ability of betulinic acid to inhibit STAT3 activation and rescued betulinic acid-induced cell death. Betulinic acid also downregulated the expression of STAT3-regulated gene products such as bcl-xL, bcl-2, cyclin D1 and survivin. This correlated with an increase in apoptosis as indicated by an increase in the sub-G1 cell population and an increase in caspase-3-induced PARP cleavage. Consistent with these results, overexpression of constitutive active STAT3 significantly reduced the betulinic acid-induced apoptosis. Betulinic acid also enhanced the apoptosis induced by thalidomide (from 10 to 55%) and bortezomib (from 5 to 70%) in MM cells. Overall, our results suggest that betulinic acid downregulates STAT3 activation through upregulation of SHP-1, and this may have potential in sensitization of STAT3 overexpressing tumors to chemotherapeutic agents.

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PMID: 

Mol Nutr Food Res. 2009 Jan ;53(1):140-6. PMID: 19065582

Abstract Title: 

Betulinic acid: a natural product with anticancer activity.

Abstract: 

Betulinic acid (BA) is a naturally occurring pentacyclic triterpene that exhibits a variety of biological activities including potent antitumor properties. This anticancer activity has been linked to its ability to directly trigger mitochondrial membrane permeabilization, a central event in the apoptotic process that seals the cell's fate. In contrast to the potent cytotoxicity of BA against a variety of cancer types, nonmalignant cells and normal tissue remained relatively resistant to BA, indicating a therapeutic window. Since agents that exert a direct action on mitochondria may trigger cell death under circumstances in which standard chemotherapeutics fail, there is increasing interest to develop such compounds as experimental cancer therapeutics. Thus, mitochondrion-targeted agents such as BA hold great promise as a novel approach to bypass certain forms of drug resistance in human cancers.

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PMID: 

Biomed Pharmacother. 2016 Dec ;84:1533-1537. Epub 2016 Nov 18. PMID: 27876208

Abstract Title: 

Betulinic acid protects against cerebral ischemia/reperfusion injury by activating the PI3K/Akt signaling pathway.

Abstract: 

Betulinic acid (BA), a naturally occurring pentacyclic lupane group triterpenoid, has been demonstrated to protect against ischemia/reperfusion-induced renal damage. However, the effects of BA on cerebral ischemia/reperfusion (I/R) injury remain unclear. Hence, this study was to investigate the effects of BA on oxygen and glucose deprivation/reperfusion (OGD/R) induced neuronal injury in rat hippocampal neurons. Our results showed that BA pretreatment greatly attenuated OGD/R-induced neuronal injury. BA also inhibited OGD/R-induced intracellular ROS production and MDA level in rat hippocampal neurons. Furthermore, the down-regulation of Bcl-2, up-regulation of Bax and the consequent activation of caspase-3 induced by OGD/R were reversed by BA pretreatment. Mechanistic studies demonstrated that BA pretreatment up-regulated the expression levels of p-PI3K and p-Akt in hippocampal neurons induced by OGD/R. Taken together, these data suggested that BA inhibits OGD/R-induced neuronal injury in rat hippocampal neurons through the activation of PI3K/Akt signaling pathway.

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PMID: 

Oncol Res. 2017 Aug 7 ;25(7):1141-1152. Epub 2017 Jan 20. PMID: 28109089

Abstract Title: 

Betulinic Acid Inhibits Cell Proliferation in Human Oral Squamous Cell Carcinoma via Modulating ROS-Regulated p53 Signaling.

Abstract: 

Oral squamous cell carcinoma (OSCC) is a common cancer of the head and neck. Betulinic acid (BA) is a naturally occurring pentacyclic triterpenoid. The present study was designed to explore the effects of BA on OSCC KB cell proliferation in vitro and on implanted tumor growth in vivo and to examine the possible molecular mechanisms. The results showed that BA dose-dependently inhibited KB cell proliferation and decreased implanted tumor volume. In addition, BA significantly promoted mitochondrial apoptosis, as reflected by an increase in TUNEL+ cells and the activities of caspases 3 and 9, an increase in Bax expression, and a decrease in Bcl-2 expression and the mitochondrial oxygen consumption rate. BA significantly increased cell population in the G0/G1 phase and decreases the S phase cell number, indicating the occurrence of G0/G1 cell cycle arrest. ROS generation was significantly increased by BA, and antioxidant NAC treatment markedly inhibited the effect of BA on apoptosis, cell cycle arrest, and proliferation. BA dose-dependently increased p53 expression in KB cells and implanted tumors. p53 reporter gene activity and p53 binding in the promoters of Bax were significantly increased by BA. Knockdown of p53 blocked BA-induced increase in apoptosis, cell cycle arrest, and inhibition of cell proliferation. NAC treatment suppressed BA-induced increase in p53 expression. Furthermore, phosphorylation of signal transducer and activator of transcription 3 (STAT3) was increased by BA. Taken together, the data demonstrated that ROS-p53 signaling was crucial for BA-exhibited antitumor effect in OSCC. BA may serve as a potential drug for the treatment of oral cancer.

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PMID: 

Molecules. 2017 Feb 10 ;22(2). Epub 2017 Feb 10. PMID: 28208611

Abstract Title: 

Betulinic Acid-Mediated Apoptosis in Human Prostate Cancer Cells Involves p53 and Nuclear Factor-Kappa B (NF-κB) Pathways.

Abstract: 

Defects in p53 and nuclear factor-kappa B (NF-κB) signaling pathways are frequently observed in the initiation and development of various human malignancies, including prostate cancer. Clinical studies demonstrate higher expression of NF-κB/p65/RelA, NF-κB/p50/RelB, and cRel as well as downregulation of the p53 network in primary prostate cancer specimens and in metastatic tumors. Betulinic acid (BA), is a triterpenoid that has been reported to be an effective inducer of apoptosis through modification of several signaling pathways. Our objective was to investigate the pathways involved in BA-induced apoptosis in human prostate cancer cells. We employed the androgen-responsive LNCaP cells harboring wild-type p53, and androgen-refractory DU145 cells possessing mutated p53 with high constitutive NF-κB activity. Inhibition of cell survival by BA at 10 and 20 µM concentrations occurred as a result of alteration in Bax/Bcl-2 ratio inboth cell lines that led to an increased cytochrome C release, caspase activation and poly(ADP)ribose polymerase (PARP) cleavage, leading to apoptosis. BA treatment resulted in stabilization of p53 through increase in phosphorylation at Ser15 in LNCaP cells, but not in DU145 cells, and induction ofcyclin kinase inhibitor p21/Waf1 in both cell types. Furthermore, treatment of both prostate cancer cells with BA decreased the phosphorylation of IκB kinase (IKK)α and I-kappa-B-alpha (IκBα) inhibiting the nuclear location of NF-κB/p65 causing cytosolic accumulation and resulting in its decreased nuclear binding. We demonstrate that BA may induce apoptosis by stabilizing p53 and downregulating NF-κB pathway in human prostate cancer cells, irrespective of the androgen association, and therefore can potentially be developed as a molecule of interest in cancer chemoprevention.

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PMID: 

Biomed Pharmacother. 2017 Apr ;88:349-358. Epub 2017 Jan 21. PMID: 28119237

Abstract Title: 

Betulinic acid promotes TRAIL function on liver cancer progression inhibition through p53/Caspase-3 signaling activation.

Abstract: 

Betulinic acid (BA), isolated from the tree bark, is a pentacyclic triterpenoid, showing inhibitory role in cancer cells. However, the effects of BA treatment on liver cancer have little to be known. Thus, the study is conducted to explore the in vitro and in vivo role of BA in liver cancer. And the interactions between BA and tumor necrosis factor-related apoptosis-inducing ligand of APO2, also known as TRAIL, were investigated in liver cancer cells. A synergistic effect of BA and APO2 combination on apoptosis induction in liver cancer cells was observed. The cancer cells were insensitive to APO2 single therapy. However, liver cancer cells receiving BA were sensitive to APO2-triggered apoptotic response by enhancing Caspases cleavage, due to elevation of decoy receptor 1 and 2 (DcR1 and DcR2) dependent on p53. Bcl-2 family members of Bcl-2 and Mcl-1, belonging to anti-apoptosis, were decreased, whereas Bad and Bak, as pro-apoptotic members, were increased for BA and APO2 combined treatment. Additionally, the mouse xenograft model suggested that BA and APO2 in combination markedly inhibited liver cancer growth in comparison to BA or APO2 monotherapy without toxicity. The present study revealed a dramatically therapeutic strategy for promoting APO2-induced anti-cancer effects on liver cancer cells via BA combination.

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PMID: 

Transplantation. 2015 Apr ;99(4):724-30. PMID: 25340603

Abstract Title: 

Removal of donor human leukocyte antigen class I proteins with papain: translation for possible whole organ practices.

Abstract: 

BACKGROUND: Papain is a protease with potential use in transplantation because of its targeted capacity to selectively remove human leukocyte antigen (HLA) class I proteins from donor human cells. However, its proteolytic activity has not been studied under conditions suitable for use in perfusing donor organs, namely, under a temperature of 4°C and dissolution in Belzer-UW solution.METHODS: We test papain's HLA class I removing activity under recognized whole organ transplant conditions of lowered temperature. The activity of papain's substrate selectivity was tested using both a test substrate (casein) and fresh peripheral blood lymphocytes (PBLs). The activity of papain was also tested at 4°C, the temperature of whole organ storage.RESULTS: We found that papain at a range of concentrations is nearly as active in cleaving the test substrate in Belzer-UW solution as in distilled water. In distilled water, papain is as active in cleaving a test substrate at a temperature of 4°C as compared to its optimal temperature of 37°C, if the incubation time is extended from 10 min to 3 hr. This finding also holds true if papain is dissolved in Belzer-UW solution. In peripheral blood lymphocytes, papain cleaved off HLA class I proteins as effectively at 4°C as at 37°C, provided the incubation time was also extended to 3 hr.CONCLUSION: These findings suggest that papain's targeted enzymatic cleavage of donor HLA class I has potential use in the whole organ transplant setting with retained activity at lower temperatures and when activated and dissolved in Belzer-UW solution.

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PMID: 

Life Sci. 2018 Sep 15 ;209:24-33. Epub 2018 Aug 1. PMID: 30076920

Abstract Title: 

Betulinic acid as apoptosis activator: Molecular mechanisms, mathematical modeling and chemical modifications.

Abstract: 

A natural product betulinic acid (BA) has gained a huge significance in the recent years for its strong cytotoxicity. Surprisingly, in spite of being an interesting cancer protecting agent on a variety of tumor cells, the normal cells and tissues are rarely affected by BA. Betulinic acid and analogues (BAs) generally exert through the mechanisms that provokes an event of direct cell death and bypass the resistance to normal chemotherapeutics. Although the major mechanism associated with its ability to induce direct cell death is mitochondrial apoptosis, there are several other mechanisms explored recently. Importantly, mathematical modeling of apoptosis has been an important tool to explore the precise mechanism involved in mitochondrial apoptosis. Thus, this review is an endeavor to sum up the molecular mechanisms underlying the action of BA and future directions to apply mathematical modeling technique to better understand the precise mechanism of BA-induced apoptosis. The last section of the review encompasses the plausible structural modifications and formulations to enhance the therapeutic efficacy of BA.

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PMID: 

J Biol Chem. 2004 Mar 19 ;279(12):11521-9. Epub 2003 Dec 30. PMID: 14701849

Abstract Title: 

Mitochondrial pH monitored by a new engineered green fluorescent protein mutant.

Abstract: 

We here describe a new molecularly engineered green fluorescent protein chimera that shows a high sensitivity to pH in the alkaline range. This probe was named mtAlpHi, for mitochondrial alkaline pH indicator, and possesses several key properties that render it optimal for studying the dynamics of mitochondrial matrix pH, e.g. it has an apparent pK(a) (pK(a)') around 8.5, it shows reversible and large changes in fluorescence in response to changes in pH (both in vitro and in intact cells), and it is selectively targeted to the mitochondrial matrix. Using mtAlpHi we could monitor pH changes that occur in the mitochondrial matrix in a variety of situations, e.g. treatment with uncouplers or Ca(2+) ionophores, addition of drugs that interfere with ATP synthesis or electron flow in the respiratory chain, weak bases or acids, and receptor activation. We observed heterogeneous pH increases in the mitochondrial matrix during Ca(2+) accumulation by this organelle. Finally, we demonstrate that Ca(2+) mobilization from internal stores induced by ionomycin and A23187 cause a dramatic acidification of the mitochondrial matrix.

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