Exploring the efficacy of combination therapy for DNA crosslinking drug mitomycin C (or antimetabolite drug 5-fluorouracil) and the synthetic strategies for crosslinked oligonucleotide duplex

 The recent surge in interest in herbal medicine stems from an increased curiosity in determining whether the efficacy of anticancer drugs could be augmented via additional ingredients.  In the case of digestion, effective processing of nutrients obtained through the diet may require additional components (ex. vitamin C), some of which serve as co-factors for enzymatic catalysis.  Given the high rate of cancer-associated mortality that remains unabated over the years (~608,000 deaths in the U.S. alone in 2021), additional means of improving current therapeutic regimens are being sought (Siegel et al, 2021).   Worldwide, the number of casualties due to cancer is projected to increase from 9.5 million (2018) to 16.3 million deaths by the year 2040 (https://www.cancer.org/research/cancer-facts-statistics/global.html).

Of interest in this regard is herbal medicine, which contains additional ingredients besides the active component, whose impact on the therapeutic efficacy of the latter remains largely unexplored.  The therapeutic potential of various plants and other biological resources has been recognized for thousands of years globally.  This has led to the curating of therapeutic regimens dubbed 'ancient medicine' for various illnesses in multiple continents including Asia, Africa, the Americas, and Europe (Wargovich et al., 2001).

Numerous herbal products have been examined for potential anticancer effects through preclinical or clinical studies.  These include mistletoe, green tea extract, phytoestrogens, and others. (Olaku et al., 2011).  Sage (Salvia officinalis) is an evergreen shrub found in the Mediterranean region in Europe and elsewhere.  Since ancient times, it has been used in religious rituals, cuisine, or herbal medicine (ex. fever).  A preclinical study showed that essential oil distilled from sage leaves (containing multiple components including flavonoid glycosides, estrogenic substance, fumaric acid) suppresses the growth of colon cancer cells (Luca et al., 2020).

Traditional Chinese medicine (TCM) encompasses an extensive array of plants with potential therapeutic values for various illnesses including cardiovascular disease, inflammation, diabetes, and cancer (Luo et al., 2019).  Malaria is a life-threatening disease caused by a single celled organism (protozoa) that infects and develops within red blood cells.  Despite the centuries-old practice of treating malaria with chloroquine, the occurrence of resistant strains presented a significant clinical challenge in the 1960s.  The discovery of artemisinin from the medicinal herb Artemisia annua by Y. Tu and colleagues (China Academy of Traditional Chinese Medicine; Nobel prize 2015) as a novel anti-malarial agent provided a necessary therapeutic relief to millions of afflicted patients globally (Miotto et al., 2015).


Among the best characterized traditional Chinese medicines is green tea extract (Wagner et al., 2011)  EGCG (epigallocatechin-3-gallate) is the main polyphenol compound found in green tea extract, which has been extensively studied for its pharmacological properties (ex. anti-obesity, anti-inflammatory, anti-diabetic, anti-viral) though its excessive intake may lead to liver toxicity.  The anti-oxidative property of EGCG results from the ability of the dihydroxy and trihydroxy groups present in its ring structure to scavenge radicals or chelate ions (Ouyang et al., 2020).  Multiple reports have examined its growth inhibitory effect on breast cancer, lymphoma, gastric cancer, bladder cancer, etc. (Luo et al., 2019).   More recently, its suppressive effect of various pathogenic viruses including COVID-19 coronavirus has been studied (Mhatre et al, 2020).

 Of interest is this regard is triterpene saponin isolated from the leaves or stems of Silphium radula Nutt, some of which exhibited antiproliferative properties against breast cancer cell lines (Cababria et al., 2008).  The utility of phenolic acids (or flavonoids) in the taxonomic classification of the plant species Silphium was previously described (Williams et al., 2009).

 ‘Biological response modifer’ typically refers to immune response modulators.  Hence,  interferons, antibodies, vaccines, etc. that are administered to boost patients’ anti-tumor immune response fall into this category.  In a similar vein, the ability of lentinan (β- 1,  3- D-glucan polymer consisting of β- 1, 4 or β- 1, 6 branches), an ingredient found in the fungus Lentinula edodes (a.k.a. Shiitake mushroom, Japan), to function as an adjuvant for chemotherapy was investigated.  A retrospective meta-analysis (pooling of data from independent studies) of 650 gastric cancer patients (Japan) treated with the DNA damaging agent mitomycin C (DNA crosslinker) or the antimetabolite drug Tegafur (prodrug of 5-fluorouracil; interferes with DNA replication) found that it increased 1-year survival rate and reduced treatment-associated side effects (Wang et al., 2017).  The preparatory procedure for crosslinked oligodeoxynucleotides for pharmacological studies described by P. Miller (Johns Hopkins University, USA) is shown in Figure (Noll et al., 2004).

 Among various complementary and alternative medicine, herbal medicine has been used in a significant fraction of cancer patients in Europe.  For colorectal cancer patients, ~48% used herbal medicine for improving physical condition or therapy potentially (Molassiotis et al., 2005).  A similar percentage of lung cancer patients have used herbal medicine (Molassiotis et al., 2006).  Nevertheless, herbal products are not free of side effects, and pharmacological mechanism as well as potential toxicity should be carefully assessed before using as single agent or combination therapy.


The key to preventing epidemic is the ability to diagnose the infected early to preempt further propagation.  For this, Bio-Synthesis, Inc. provides primers and probes (as well as synthetic RNA control) for COVID-19 diagnosis via RT-PCR assay.  It specializes in oligonucleotide modification and provides an extensive array of chemically modified nucleoside analogues (over ~200) including bridged nucleic acid (BNA) in addition to mRNA synthesis.  A number of options are available to label oligonucleotides (DNA or RNA) with fluorophores either terminally or internally as well as to conjugate to peptides or antibodies. It provides custom conjugation of small molecules such as chemical drugs, metabolites and labeled compounds with synthetic or natural polymers (enzymes, peptide, protein, oligonucleotide, antibody, dendrimer, nanoparticle, etc).  It recently acquired a license from BNA Inc. of Osaka, Japan, for the manufacturing and distribution of BNANC, a third generation of BNA oligonucleotides.  To meet the demands of therapeutic application, its oligonucleotide products are approaching GMP grade.  It has recently entered into collaborative agreement with Bind Therapeutics, Inc. to synthesize miR-21 blocker using BNA for triple negative breast cancer.  The BNA technology provides superior, unequalled advantages in base stacking, binding affinity, aqueous solubility and nuclease resistance.  It also improves the formation of duplexes and triplexes by reducing the repulsion between the negatively charged phosphates of the oligonucleotide backbone.  Its single-mismatch discriminating power is especially useful for diagnosis (ex. FISH using DNA probe).  For clinical application, BNA oligonucleotide exhibits lesser toxicity than other modified nucleotides. 













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