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The NADPH-oxidase 1 (Nox1) is a homolog of gp91phox, the catalytic subunit of the phagocyte superoxide-generating NADPH-oxidase. Nox1 is expressed in normal colon epithelial cells and in colon tumor cell lines, and overexpression in model cells has been implicated in stimulation of mitogenesis and angiogenesis and inhibition of apoptosis. This suggests that aberrant expression of Nox1 could contribute to the development of colorectal cancer. Herein, we examine the expression of Nox1 mRNA in 24 colon tumors of various stages compared with paired adjacent normal tissue from the same patient, and correlate expression with some common mutations associated with colon cancer. Nox1 was overexpressed compared with paired normal tissue in 57% of tumors as early as the adenoma stage, with no correlation of expression level with tumor stage. Overexpression of Nox1 mRNA correlated with Nox1 protein levels assessed by immunofluorescence and immunohistochemistry with an antibody specific for Nox1. There was a strong correlation between Nox1 mRNA level and activating mutations in codons 12 and 13 of K-Ras. Eighty percent (8/10) of tumors with codons 12 and 13 mutations had a 2-fold or more increase in Nox1 mRNA, and 70% (7/10) had a 5-fold or greater increase. Transgenic mice expressing K-RasG12V in the intestinal epithelium also expressed markedly elevated Nox1 in both small and large intestine. There was no correlation between inactivating mutations in the tumor suppressor p53 and Nox1 expression. We conclude that Nox1 mRNA and protein are overexpressed in colon cancer and are strongly correlated with activating mutations in K-Ras.

Waardenburg syndrome (WS) is an autosomal-dominant disorder characterized by sensorineural hearing loss, dystopia canthorum, and pigmentary disturbances, and it represents the most common form of inherited deafness in infants. WS type I is characterized by the presence of dystopia canthorum, while individuals with WS type II have normally-located canthi. WS type III is similar to WS type I but is also characterized by musculoskeletal abnormalities. Defects in the PAX3 gene, a transcription factor expressed during embryonic development, have been shown to cause WS types I and III in several families. In contrast, mutations in PAX3 do not cause WS type II, and linkage of the disease to other chromosomal regions has been demonstrated. We describe 10 additional mutations in the PAX3 gene in families with WS type I. Eight of these mutations are in the region of PAX3, where only one mutation has been previously described. These mutations, together with those previously reported, cover essentially the entire PAX3 gene and represent a wide spectrum of mutations that can cause WS type I. Thus far, all but one of the mutations are private; only one mutation has been reported in two apparently unrelated families. Our analysis thus far demonstrates little correlation between genotype and phenotype; deletions of the entire PAX3 gene result in phenotypes indistinguishable from those associated with single-base substitutions in the paired domain or homeodomain of PAX3. Moreover, two similar mutations in close proximity can result in significantly different phenotypes, WS type I in one family and WS type III in another.

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