Abstract
BackgroundThe highly valued medicinal tiger milk mushroom (also known as Lignosus rhinocerus) has the ability to cure numerous ailments. Its anticancer activities are well explored, and recently a partially purified cytotoxic protein fraction termed F5 from the mushroom’s sclerotial cold water extract consisting mainly of fungal serine proteases was found to exhibit potent selective cytotoxicity against a human breast adenocarcinoma cell line (MCF7) with IC50 value of 3.00 μg/ml. However, characterization of its cell death-inducing activity has yet to be established.MethodsThe mechanism involved in the cytotoxic activities of F5 against MCF7 cells was elucidated by flow cytometry-based apoptosis detection, caspases activity measurement, and expression profiling of apoptosis markers by western blotting. Molecular attributes of F5 were further mined from L. rhinocerus’s published genome and transcriptome for future exploration.Results and DiscussionApoptosis induction in MCF7 cells by F5 may involve a cross-talk between the extrinsic and intrinsic apoptotic pathways with upregulation of caspase-8 and -9 activities and a marked decrease of Bcl-2. On the other hand, the levels of pro-apoptotic Bax, BID, and cleaved BID were increased accompanied by observable actin cleavage. At gene level, F5 composed of three predicted non-synonymous single nucleotide polymorphisms (T > C) and an alternative 5′ splice site.ConclusionsFindings from this study provide an advanced framework for further investigations on cancer therapeutics development from L. rhinocerus.
Highlights
The World Health Organization reported that breast cancer is the most prevalent form of cancer in women both in the developed and developing world where an estimated of 1.6 million new cases are diagnosed worldwide each year
We further investigated the mechanism involved in the cytotoxic activities of this protein against MCF7 cells and based on the recently available of L. rhinocerus genome and transcriptome (Yap et al, 2014, 2015a), we included more details of the
Three non-synonymous single nucleotide polymorphisms (SNPs) from thymine (T) to cytosine (C) were detected at the 126772th, 127822th, and 128424th bp of the 18th scaffold (Fig. S1) in between different samples of the same cultivar with SOAPsnp (Li et al, 2009) and an alternative 5′ splice site in the 12th coding region of GME4347_g at 128457th bp instead of the regular 5′-end at 128453th bp which could result in two different transcripts were listed
Summary
The World Health Organization reported that breast cancer is the most prevalent form of cancer in women both in the developed and developing world (http://www.who.int/ cancer/detection/breastcancer/en/) where an estimated of 1.6 million new cases are diagnosed worldwide each year. L. rhinocerus, more commonly known as the tiger milk mushroom, is one of the most valuable medicinal mushrooms used by the local communities in Southeast Asia (e.g., the Semai, Temuan, and Jakun native communities in Malaysia) (Chang & Lee, 2004) to cure numerous ailments including gastric ulcers, wounds, chronic hepatitis, fever, whooping cough, asthma, cancer, and food poisoning (Jones, Hyde & Sabaratnam, 2007; Wong & Cheung, 2009) This white-rot fungus (Class: Basidiomycetes; Family: Polyporaceae) consists of a centrally stipitate pilei that arises from a submerged sclerotium which is the part with medicinal value. Its anticancer activities are well explored, and recently a partially purified cytotoxic protein fraction termed F5 from the mushroom’s sclerotial cold water extract consisting mainly of fungal serine proteases was found to exhibit potent selective cytotoxicity against a human breast adenocarcinoma cell line (MCF7) with IC50 value of 3.00 mg/ml. Conclusions: Findings from this study provide an advanced framework for further investigations on cancer therapeutics development from L. rhinocerus
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