Colorectal cancer (CRC) is one the greatest contributors to cancer related mortality. Although 5 year survival rate for patients at the early stage of CRC (stages I and II) is above 60%, more than 50% of patients are diagnosed at or beyond stage III when distant metastasis has already occurred, in which case 5 year survival rate drops to 10%. Chemotherapeutic intervention coupled with surgery is the backbone of metastatic CRC treatment and the only means of enhanced survival. For decades following its discovery, an antimetabolite 5- fluorouracil (5-FU) was the only chemotherapeutic agent available to successfully improve 12 month survival in CRC patients. Treatment of metastatic CRC has been considered palliative for many years; aiming to increase the duration and quality of the patient's remaining life, with little hope of cure, highlighting the need for novel DNA and RNA targeted therapies in the treatment of CRC. Over the last several decades, combinations of several chemotherapeutic agents have been incorporated into routine clinical practice. Combination regimes incorporating irinotecan, a semisynthetic inhibitor of topoisomerase, oxaliplatin, a third-generation platinum compound that causes mitotic arrest via the formation of DNA adducts, and capecitabine, a 5-FU prodrug, are now all established options for use as first-line, second-line and sequential treatment of CRC. This review provides a brief overview of the evolution of CRC chemotherapy as well as new and emerging treatment options.

The distribution of nitric oxide synthase (NOS) immunoreactivity was investigated in the guinea-pig small intestine. There were many immunoreactive nerve cell bodies in the myenteric plexus but very few in submucous ganglia. NOS immunoreactivity was not found in non-neuronal cells except for rare mucosal endocrine cells. Abundant immunoreactive nerve fibres in both myenteric and submucous ganglia, and in the circular muscle, arose from myenteric nerve cells whose axons projected anally along the intestine. NOS immunoreactivity coexisted with VIP-immunoreactivity, but not with substance P immunoreactivity. We conclude that nitric oxide synthase is located in a sub-population of enteric neurons, amongst which are inhibitory motor neurons that supply the circular muscle layer.

Gastrointestinal (GI) side-effects of chemotherapy are a debilitating and often overlooked clinical hurdle in cancer management. Chemotherapy-induced constipation (CIC) and diarrhoea (CID) present a constant challenge in the efficient and tolerable treatment of cancer and are amongst the primary contributors to dose reductions, delays and cessation of treatment. Although prevalence of CIC is hard to estimate, it is believed to affect approximately 16% of cancer patients, whilst incidence of CID has been estimated to be as high as 80%. Despite this, the underlying mechanisms of both CID and CIC remain unclear, but are believed to result from a combination of intersecting mechanisms including inflammation, secretory dysfunctions, GI dysmotility and alterations in GI innervation. Current treatments for CIC and CID aim to reduce the severity of symptoms rather than combating the pathophysiological mechanisms of dysfunction, and often result in worsening of already chronic GI symptoms or trigger the onset of a plethora of other side-effects including respiratory depression, uneven heartbeat, seizures and neurotoxicity. Emerging treatments including those targeting the enteric nervous system present promising avenues to alleviate CID and CIC. Identification of potential targets for novel therapies to alleviate chemotherapy-induced toxicity is essential to improve clinical outcomes and quality of life amongst cancer sufferers.