Radha Munagala

Withaferin A induces p53-dependent apoptosis by repression of HPV oncogenes and upregulation of tumor suppressor proteins in human cervical cancer cells

Cervical cancer is caused by human papilloma virus (HPV) expressing E6 and E7 oncoproteins, which are known to inactivate tumor suppressor proteins p53 and pRb, respectively. Repression of HPV oncoproteins would therefore result in reactivation of tumor suppressor pathways and cause apoptosis in cancer cells. Withaferin A (WA), the active component of the medicinal plant Withania Somnifera, has exhibited inhibitory effects against several different cancers. We examined the activity of WA on human cervical cancer cells in vitro and in vivo. WA potently inhibited proliferation of the cervical cancer cells, CaSki (IC(50) 0.45 ± 0.05 μM). Mechanistically, WA was found to (i) downregulate expression of HPV E6 and E7 oncoproteins, (ii) induce accumulation of p53, (iii) increase levels of p21(cip1/waf1) and its interaction with proliferating cell nuclear antigen (PCNA), (iv) cause G(2)/M cell cycle arrest, associated with modulation of cyclin B1, p34(cdc2) and PCNA levels, (v) decrease the levels of STAT3 and its phosphorylation at Tyr(705) and Ser(727) and (vi) alter expression levels of p53-mediated apoptotic markers-Bcl2, Bax, caspase-3 and cleaved PARP. In vivo, WA resulted in reduction of nearly 70% of the tumor volume in athymic nude mice with essentially similar trend in the modulation of molecular markers as in vitro. This is the first demonstration indicating that WA significantly downregulates expression of HPV E6/E7 oncogenes and restores the p53 pathway, resulting in apoptosis of cervical cancer cells. Together, our data suggest that WA can be exploited as a potent therapeutic agent for the treatment and prevention of cervical cancer without deleterious effects.

Bovine milk-derived exosomes for drug delivery

Exosomes are biological nanovesicles that are involved in cell-cell communication via the functionally-active cargo (such as miRNA, mRNA, DNA and proteins). Because of their nanosize, exosomes are explored as nanodevices for the development of new therapeutic applications. However, bulk, safe and cost-effective production of exosomes is not available. Here, we show that bovine milk can serve as a scalable source of exosomes that can act as a carrier for chemotherapeutic/chemopreventive agents. Drug-loaded exosomes showed significantly higher efficacy compared to free drug in cell culture studies and against lung tumor xenografts in vivo. Moreover, tumor targeting ligands such as folate increased cancer-cell targeting of the exosomes resulting in enhanced tumor reduction. Milk exosomes exhibited cross-species tolerance with no adverse immune and inflammatory response. Thus, we show the versatility of milk exosomes with respect to the cargo it can carry and ability to achieve tumor targetability. This is the first report to identify a biocompatible and cost-effective means of exosomes to enhance oral bioavailability, improve efficacy and safety of drugs.

Antioxidant and Antiproliferative Activities of Anthocyanin/Ellagitannin-Enriched Extracts From Syzygium cumini L. (Jamun, the Indian Blackberry)

Colored fruits, particularly berries, are highly chemoprotective because of their antioxidant, antiproliferative, and antiinflammatory activities. We report the cancer chemoprotective potential of Syzygium cumini L., commonly known as jamun or Indian blackberry. Anthocyanins and other polyphenolics were extracted with acidic ethanol and enriched by amberlite XAD7/HP20 (1:1). The pulp powder was found to contain 0.54% anthocyanins, 0.17% ellagic acid/ellagitannins, and 1.15% total polyphenolics. Jamun seed contained no detectable anthocyanins but had higher amounts of ellagic acid/ellagitannins (0.5%) and total polyphenolics (2.7%) than the pulp powder. Upon acid hydrolysis, the pulp extract yielded 5 anthocyanidins by HPLC: malvidin (44.4%), petunidin (24.2%), delphinidin (20.3%), cyanidin (6.6%), and peonidin (2.2%). Extracts of both jamun pulp (1,445 ± 64 μmol of trolox equivalent (TE)/g) and seeds (3,379 ± 151 μM of TE/g) showed high oxygen radical absorbance capacity. Their high antioxidant potential was also reflected by 2,2’-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid)- and 2,2-diphenyl-1-picrylhydrazyl-scavenging and ferrous ion-chelating activities. We also analyzed antiproliferative activity of jamun extracts against human lung cancer A549 cells. The hydrolyzed pulp and seed extracts showed significant antiproliferative activity. However, unhydrolyzed extracts showed much less activity. These data showed that in addition to 5 anthocyanidins, jamun contains appreciable amounts of ellagic acid/ellagitannins, with high antioxidant and antiproliferative activities.

Bioavailability of phytochemicals and its enhancement by drug delivery systems

Issues of poor oral bioavailability of cancer chemopreventives have hindered progress in cancer prevention. Novel delivery systems that modulate the pharmacokinetics of existing drugs, such as nanoparticles, cyclodextrins, niosomes, liposomes and implants, could be used to enhance the delivery of chemopreventive agents to target sites. The development of new approaches in prevention and treatment of cancer could encompass new delivery systems for approved and newly investigated compounds. In this review, we discuss some of the delivery approaches that have already made an impact by either delivering a drug to target tissue or increasing its bioavailability by many fold.

Promising molecular targeted therapies in breast cancer

In recent years, there has been a significant improvement in the understanding of molecular events and critical pathways involved in breast cancer. This has led to the identification of novel targets and development of anticancer therapies referred to as targeted therapy. Targeted therapy has high specificity for the molecules involved in key molecular events that are responsible for cancer phenotype such as cell growth, survival, migration, invasion, metastasis, apoptosis, cell-cycle progression, and angiogenesis. Targeted agents that have been approved for breast cancer include trastuzumab and lapatinib, directed against human epidermal growth factor receptor 2 (HER2) and bevacizumab, directed against vascular endothelial growth factor (VEGF). Several other targeted agents currently under evaluation in preclinical and clinical trials include inhibitors of epidermal growth factor receptor (EGFR), dual EGFR and HER2 inhibitors, VEGF/VEGFR inhibitors, and agents that interfere with crucial signaling pathways such as PI3K/AKT/mTOR and RAS/MEK/ERK; agents against other tyrosine kinases such as Src, insulin-like growth factor (IGF)/IGF-receptor (IGFR); agents that promote apoptosis such as Poly ADP ribose polymerase inhibitors; agents that target invasion and metastasis such as matrix metalloproteinases inhibitors and others. In this review, we highlight the most promising targeted agents and their combination with mainstream chemotherapeutic drugs in clinical trials.

Exosomal miRNAs as biomarkers of recurrent lung cancer.

Prognosis of lung cancer still remains grim largely due to recurrence and aggressive metastasis of the disease. In this study, we examined the potential of exosomal miRNAs as biomarkers of recurrent lung cancer. Initially, in vitro miRNA profiles of normal lung (Beas-2b) and lung cancer (H1299) cells and of exosomes isolated from conditioned media were determined. In vivo study involved establishing subcutaneous primary and recurrent lung cancer xenografts in nude mouse model and examining tumor and serum exosomal miRNA alteration in secondary/recurrent lung tumors. A total of 77 miRNAs were observed to be significantly modulated in the H1299 cells (47 miRNA upregulated and 30 downregulated) compared to the Beas-2b cells. The exosomes isolated from conditioned media indicated several miRNAs which were in agreement with cells of origin. A similarity was also observed between miRNAs from serum exosomes and tumors, indicating their origin from the lung tumors. Two miRNAs, miR-21 and miR-155, were found to be significantly upregulated in recurrent tumors compared to primary tumors. These miRNAs were also upregulated in serum exosomes of recurrent tumor-bearing animals versus non-tumor- or primary tumor-bearing animals. Increased expression of the recurrent disease markers were also observed in recurrent tumors compared with primary tumors. Serum exosomes from recurrent tumor mice mirrored its tumor profile in expressing higher levels of these proteins compared with exosomes from primary tumor mice. Our data suggest that exosomal miRNA signatures may be a true representation of a pathological profile of lung cancer; thus, miRNAs could serve as promising biomarkers for non-invasive diagnosis of the disease.

Cucurbitacin B potently suppresses non-small-cell lung cancer growth: Identification of intracellular thiols as critical targets

Cucurbitacin B (CuB), has recently emerged as a potent anticancer agent; however, its efficacy in non-small-cell lung cancer (NSCLC) and the mechanism(s) initiating its biological effects remain largely unclear. In this study, CuB potently suppressed the growth of four NSCLC cells (H1299, A549, HCC-827 and H661) in vitro and the highly aggressive H1299 xenograft in vivo. CuB significantly altered the actin cytoskeletal assembly, induced G2/M cell-cycle arrest and mitochondrial apoptosis through the modulation of several key molecular targets mediating the aforementioned processes. Interestingly, all cellular effects of CuB were completely attenuated only by the thiol antioxidant N-acetylcysteine (NAC). Furthermore, pretreatment with glutathione synthesis inhibitor butithione-sulfoxime (BSO), significantly exacerbated CuBs cytotoxic effects. To this end, cells treated with CuB revealed a rapid and significant decrease in the levels of protein thiols and GSH/GSSG ratio, suggesting disruption of cellular redox balance as the primary event in CuBs cytotoxic arsenal. Using UV and FTICR mass spectrometry we also demonstrate for the first time a physical interaction of CuB with NAC and GSH in a cell-free system suggesting that CuB interacts with and modulates cellular thiols to mediate its anti-cancer effects. Collectively, our data sheds new light on the working mechanisms of CuB and demonstrate its therapeutic potential against NSCLC.

Tanshinone IIA inhibits viral oncogene expression leading to apoptosis and inhibition of cervical cancer

Human papilloma virus (HPV) is the well-established etiological factor of cervical cancer. E6 and E7 oncoproteins expressed by HPV are known to inactivate tumor suppressor proteins p53 and pRb, respectively. Tanshinone IIA (Tan IIA) is a diterpenoid naphthoquinone found in the traditional Chinese medicine Danshen (Salvia sp.). Tan IIA has been shown to possess anti-tumor activity against several cancer types. In this study we show that Tan IIA potently inhibited proliferation of the human cervical cancer CaSki, SiHa, HeLa and C33a cells. Mechanistically in HPV positive CaSki cells, Tan IIA was found to (i) downregulate expression of HPV E6 and E7 genes and modulate associated proteins E6AP and E2F1, (ii) cause S phase cell cycle arrest, (iii) induce accumulation of p53 and alter expression of p53-dependent targets, (iv) modulate pRb and related proteins, and (v) cause p53-mediated apoptosis by moderating Bcl2, Bax, caspase-3, and PARP cleavage expressions. In vivo, Tan IIA resulted in over 66% reduction in tumor volume of cervical cancer xenograft in athymic nude mice. Tan IIA treated tumor tissues had lower expression of proliferation marker PCNA and changes in apoptosis targets were in agreement with in vitro studies, further confirming reduced proliferation and involvement of multiple targets behind anti-cancer effects. This is the first demonstration of Tan IIA to possess significant anti-viral activity by repressing HPV oncogenes leading to inhibition of cervical cancer. Together, our data suggest that Tan IIA can be exploited as a potent therapeutic agent for the prevention and treatment of cervical and other HPV-related cancers.

Exosomal formulation enhances therapeutic response of celastrol against lung cancer

Celastrol (CEL), a plant-derived triterpenoid, is a known inhibitor of Hsp90 and NF-κB activation pathways and has recently been suggested to be of therapeutic importance in various cancers. However, the molecular mechanisms of celastrol-mediated effects in lung cancer are not systematically studied. Moreover, it suffers from poor bioavailability and off-site toxicity issues. This study aims to study the effect of celastrol loaded into exosomes against two non-small cell-lung carcinoma (NSCLC) cell lines and explore the molecular mechanisms to determine the proteins governing the cellular responses. We observed that celastrol inhibited the proliferation of A549 and H1299 NSCLC cells in a time- and concentration-dependent manner as indexed by MTT assay. Mechanistically, CEL pre-treatment of H1299 cells completely abrogated TNFα-induced NF-κB activation and upregulated the expression of ER-stress chaperones Grp 94, Grp78, and pPERK. These changes in ER-stress mediators were paralleled by an increase in apoptotic response as evidenced by higher annexin-V/PI positive cells evaluated by FACS and immunoblotting which showed upregulation of the ER stress specific pro-apoptotic transcription factor, GADD153/CHOP and alteration of Bax/Bcl2 levels. Exosomes loaded with CEL exhibited enhanced anti-tumor efficacy as compared to free CEL against lung cancer cell xenograft. CEL did not exhibit any gross or systemic toxicity in wild-type C57BL6 mice as determined by hematological and liver and kidney function test. Together, our data demonstrate the chemotherapeutic potential of CEL in lung cancer and that exosomal formulation enhances its efficacy and reduces dose related toxicity.

Controlled-release systemic delivery - a new concept in cancer chemoprevention.

Many chemopreventive agents have encountered bioavailability issues in pre-clinical/clinical studies despite high oral doses. We report here a new concept utilizing polycaprolactone implants embedded with test compounds to obtain controlled systemic delivery, circumventing oral bioavailability issues and reducing the total administered dose. Compounds were released from the implants in vitro dose dependently and for long durations (months), which correlated with in vivo release. Polymeric implants of curcumin significantly inhibited tissue DNA adducts following the treatment of rats with benzo[a]pyrene, with the total administered dose being substantially lower than typical oral doses. A comparison of bioavailability of curcumin given by implants showed significantly higher levels of curcumin in the plasma, liver and brain 30 days after treatment compared with the dietary route. Withaferin A implants resulted in a nearly 60% inhibition of lung cancer A549 cell xenografts, but no inhibition occurred when the same total dose was administered intraperitoneally. More than 15 phytochemicals have been tested successfully by this formulation. Together, our data indicate that this novel implant-delivery system circumvents oral bioavailability issues, provides continuous delivery for long durations and lowers the total administered dose, eliciting both chemopreventive/chemotherapeutic activities. This would also allow the assessment of activity of minor constituents and synthetic metabolites, which otherwise remain uninvestigated in vivo.