- Title
- Synthesis and evaluation of norcantharidin and acrylonitrile derivatives as potential anti-cancer agents
- Creator
- Tarleton, Mark
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2012
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- Treating cancer by targeting protein phosphatases, namely protein phosphatase 1 (PP1) and protein phosphatase 2A (PP2A) is a novel ‘fighting fire with fire’ strategy. There are numerous small molecule inhibitors known to achieve this. Most important to this study, cantharidin, and its demethylated analogue, norcantharidin, offer the simplest structure for subsequent modification. The added benefit of effective membrane permeability, makes these compounds ideal candidates for further development. In contrast to most other anticancer drugs, these compounds stimulate the production of white blood cells by bone marrow, while other anticancer drugs that have the unwanted side effect of inducing myelosuppression. Cantharidin displays kidney toxicity which has prevented its use in mainstream oncology. However, norcantharidin is void of kidney toxicity allowing its development for the treatment of cancer. These biologically active compounds have been shown to have multiple uses such as the treatment of warts. Norcantharidin analogues have also been shown to display anti-parasitic activity against nematode Haemonchus contortus, the barbers pole worm, an intestinal parasite that affects livestock industries. Preliminary analysis of a norcantharidin derivative with a single reduced carbonyl group displayed selectivity towards HT29 (colon; GI₅₀ = 14μM) and SJ-G2 (glioblastoma; GI₅₀ = 15μM) when tested against the NCI 60 cell line panel. Intrigued by this finding, multiple small focused libraries were synthesised and assessed in order to compile structure activity relationships (SAR). Interestingly an analogue with an isopropyl ether showed promise with strong selectivity towards HT29 (colon; GI₅₀ = 19μM) and SJ-G2 (glioblastoma; GI₅₀ = 21μM) cell lines but completely void of activity (>100μM) against all seven remaining carcinoma cell lines tested. Norcantharidin analogues were also tested for anti-parasitic activity against Haemonchus contortus, the barbers pole worm, with multiple analogues displayed activity against Haemonchus contortus with associated LD₅₀s between 25-40 μM. The observed hit-rate of 5.6% associated with this screening of norcantharidin analogues is far higher than conventionally used drug screening methods usually employed. As part of a toxicity pre-filter, all new antiparasitic compounds are screened against a panel of ten cancer cell lines to ensure the end user was not subjected to toxic compounds being applied in a non-ideal environment such as farming communities. Surprisingly, analogues from a small acrylonitrile library, originally used as an internal standard, displayed high levels of cytotoxicity. Subsequent focused library development based on the acrylonitrile scaffold produced multiple broad spectrum cytotoxic compounds with average GI₅₀ values of 1.1-2.1 μM across the nine carcinoma cell lines examined. Interestingly, some acrylonitrile compounds showed a high degree of specificity towards MCF-7 (breast carcinoma) cells of up to 543 fold over the other carcinoma cell lines tested. Some of these compounds were further shown to selectively target estrogen dependent MCF-7 cells that over express the estrogen receptor (ER+ve) over estrogen receptor negative carcinoma (MDA-MB231) and non-malignant breast tissue (MCF10A) up to 268 and 126 fold respectively. With the high throughput of synthesised analogues, flow chemistry methodologies were developed in order to alleviate some of the associated issues with synthetic medicinal chemistry such as reproducibility between batches and difficulty in scale up for live animal studies. Along with effectively producing specific acrylonitrile derivatives in high purity and yield, these procedures were further developed in other projects leading to the discovery of the most potent protein phosphatase inhibitors developed within the research group.
- Subject
- cancer; protein phosphatases; cantharidin; anticancer drugs; thesis by publication
- Identifier
- http://hdl.handle.net/1959.13/938525
- Identifier
- uon:12632
- Rights
- Copyright 2012 Mark Tarleton
- Language
- eng
- Full Text
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| Thumbnail | File | Description | Size | Format | |||
|---|---|---|---|---|---|---|---|
| View Details Download | ATTACHMENT01 | Abstract | 3 MB | Adobe Acrobat PDF | View Details Download | ||
| View Details Download | ATTACHMENT02 | Thesis | 12 MB | Adobe Acrobat PDF | View Details Download |