ABSTRACT
Chemotherapeutic Agents ............................................................................... 52 2.6 Conclusions ..................................................................................................... 55 Acknowledgments .................................................................................................... 55 References ................................................................................................................ 56
Cancer leads to one in four deaths in the United States, and is also a major public health hazard in countries all over the world. Despite improvements in the survival rates in several major types of cancer, in the United States for the year 2009, over 560,000 deaths and nearly 1,480,000 new cancer cases were projected to occur (Jemal et al., 2009). In addition to cancer prevention and early detection, one of the strategies for improving the dire consequences of the scourge of cancer is improved treatment options inclusive of chemotherapy (Jemal et al., 2009). Natural products have played an integral role in cancer chemotherapy, not only in terms of providing new drugs and new drug leads for synthetic modi˜cation, but in also affording substances to probe cellular and molecular mechanisms of action germane to cancer inhibition (Cragg et al., 2005, 2009). In a now widely cited analysis, it was established that out of 81 nonbiological small-molecule anticancer drugs introduced into therapy in North America, western Europe, and Japan over a 25 year period from 1981 to 2006, 11.1% of these were unmodi˜ed natural products and 30.9% natural product semisynthetic derivatives, with only 22.2% classi˜ed as being totally synthetic compounds produced from an initial lead by random screening (Newman and Cragg, 2007). Several compounds of terrestrial microbe and higher plant origin are now approved as drugs in cancer chemotherapy (Cragg et al., 2005), and recently the ˜rst such marine-derived compound, ecteinascidin 743, has been approved in certain European countries for patients with advanced soft tissue sarcoma as an orphan drug (Bailly, 2009; Sashidhara et al., 2009). Judging by the relatively large number of natural products in clinical trials as potential new oncolytic agents (Butler, 2008, 2010; Harvey, 2008; Sashidhara et al., 2009), it can be expected that new natural product-derived drugs will be approved to treat cancer in the next few years, but from even more diverse types of organisms than has been the case to date.
