Specific Allelic Loss of p16 Tumor Suppressor Gene after Weeks of Iron-Mediated Oxidative Damage during Rat Renal Carcinogenesis

Abstract

Oxidative tissue damage has been shown to be associated with carcinogenesis. In human cancers p16(INK4A) is one of the most frequently mutated tumor suppressor genes. The present study used the ferric nitrilotriacetate (Fe-NTA)-induced rat renal carcinogenesis model to determine whether oxidative damage can cause specific allelic loss of p16 (INK4A). By the use of fluorescent in situ hybridization in combination with imprint cytology at single-cell resolution, we found that the number of renal tubular cells with aneuploidy (1 or 3 signals) at the p16(INK4A) locus was significantly and specifically increased (1 week, 37.2 +/- 2.3%; 3 weeks, 37.8 +/- 1.3% vs control, 22.5 +/- 1.9%; mean +/- SE, N = 8; P < 0.001 and P < 0.0001, respectively) after repeated intraperitoneal administration of 5 to10 mg of iron/kg in the form of Fe-NTA for 3 weeks. No increase in aneuploidy was observed at the loci of either the p53 or vhl tumor suppressor gene. Furthermore, the increase in the cells with 3 signals was followed by a continuous increase in those with 1 signal. Therefore, the p16 (INK4A) locus is specifically vulnerable to oxidative damage, leading to its allelic loss within weeks, presumably due to a deficiency in the replication of both the alleles.

Homozygous deletion of CDKN2A/2B is a hallmark of iron-induced high-grade rat mesothelioma

“…It is probably not a coincidence that CDKN2A/2B is a major tumor suppressor gene target in ferric nitrilotriacetate (Fe-NTA)-induced rat renal carcinogenesis model, 33 in which a major mode of inactivation is also homozygous deletion. 34,35 In the renal carcinogenesis model, an iron-catalyzed Fenton reaction is repeatedly induced in the target renal proximal tubular cells early in carcinogenesis [36][37][38] These data strongly suggest that ironmediated oxidative DNA damage is a major cause of the homozygous deletion of CDKN2A/2B. Interestingly, potassium bromate shares with iron compounds the ability to cause not only mesothlioma 28 but also renal cell carcinoma 39 presumably by oxidative stress.…”

Redox regulation of annexin 2 and its implications for oxidative stress-induced renal carcinogenesis and metastasis

“…This may be associated with the DNA repair and replication process through the activity of primer recognition, as previously described (Jindal et al, 1991). At this stage of carcinogenesis, allelic loss of p16 tumor suppressor gene is already observed (Hiroyasu et al, 2002). Intracellular localization of Anx2 appears to be closely associated with its ongoing distinct function.…”

“…Recently, we found frequent allelic losses on rat chromosomes 5 and 8 by genetic analysis of Fe-NTA-induced RCCs, which led to the conclusion that p15 INK4B and p16 INK4A (p16) tumor suppressor genes are frequently inactivated either by deletion, point mutation or methylation of the promoter region in such RCCs (Tanaka et al, 1999;Hiroyasu et al, 2002). However, since no occurrence of RCC has been observed in p16 knockout mice studies (Serrano et al, 1996;Krimpenfort et al, 2001;Sharpless et al, 2001), other alterations might also play a role in oxidative stress-induced carcinogenesis.…”

p16Ink4a overexpression in cancer: a tumor suppressor gene associated with senescence and high-grade tumors

“…p16 Ink4a inactivation has been reported to be an early and critical event in tumor progression in some types of tumors (Chao et al, 2008;Paulson et al, 2008;Guida et al, 2009;Carnero and Lleonart, 2010). In this sense, certain molecular mechanisms of p16 Ink4a repression have been directly associated with carcinogens, such as tobacco in lung cancer (Wang et al, 2005) and oxidative stress due to reactive oxygen species (Tanaka et al, 1999;Hiroyasu et al, 2002), suggesting a relevant role in the development of some preneoplastic lesions. However, p16 Ink4a inactivation has also been described as an intermediate or late event in tumor progression in pancreatic carcinoma, the tumor showing the most constant p16 Ink4a repression (Fukushima et al, 2002).…”