genotoxic and epigenetic

Overview

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Key numbers

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prior chemotherapy or radiotherapy before surgery, metastatic 5% HNO3 ) and a Hg standard solution (10 µg/ml). Working
abstracted from surgical and pathology reports and categorized 2% HNO3 . Gold was added to the acidic diluent and wash solutions
was maintained through the use of unique study identifiers. acidic diluent consisting of 0.5% nitric acid, 0.05% Triton X-100,
and 2% methanol (all v/v). Internal standards were added to all
samples were obtained from the tumor mass, while non-cancerous Calibration curves ranged from 0.25 to 4 µg/L for Pb, Cd, Hg,
tissue samples were obtained from macroscopically normal colon and As, and from 0.5 to 8 µg/L for Cr and Ti. All calibration curves
and 3 µg/L for Pb, Cd, Hg, and As; and 1.5, 3, and 6 µg/L for Cr and using a standardized protocol, and only intact, randomly selected,
ranged from 98 to 99% with relative standard deviations (%RSD) of scoring bias.
5–7% for Pb, Cd, Hg, and As, and 9%8–101% with %RSD of 2–4%
ranged from 2%−7% for Pb, Cd, Hg, and As, and from 3%−5% Genomic DNA was extracted from paired colon cancer and
solution (µg/L) were 0.017 for Pb, 0.0005 for Cd, 0.073 for Hg, DNA from colon tissues was isolated using a proteinase K
0.0078 for Ti. extraction, ethanol precipitation, washing with 70% ethanol, and
USA) containing 10% DMSO as a cryoprotectant and stored at −80 DNA methylation in peripheral blood was successfully analyzed
are therefore summarized as medians and interquartile ranges A total of 50 patients with primary colon cancer were included
(IQRs). Values below the MDL were treated as non-detects in the study. The mean age of participants was 56.9 ± 11.8 years,
and replaced with one-half of the corresponding MDL prior to and 52% were male. The mean BMI was 28.7 ± 5.0 kg/m². Most
statistical analysis. Paired comparisons between cancerous and participants were married (78%) and resided in the central region
signed-rank test. the distal colon (60%), followed by the proximal colon (30%),
Multivariable regression models were fitted using complete- with 10% involving the total colon. The majority of tumors were
case observations for the specified outcome and covariates. To low-to-intermediate grade (grades 1–2, 88%), and lymphovascular
minimize the risk of model overfitting given the sample size, invasion was present in 42% of cases. Due to variability in
Associations between tissue metal concentrations and characteristics are summarized in Table 1.
confidence intervals (95% CI) and p-values. Metal concentrations
for tumor location. Tumor location was modeled using dummy in Supplementary Table S1. When comparing paired tissues,
and indicator variables created for proximal colon and total compared with non-cancerous tissue (median 0.011 vs. 0.019 µg/g
mean of standardized (z-scored) log-transformed concentrations of As, Cr, or Ti (all p > 0.05). Detailed metal concentrations and paired
Pb, Cd, Hg, As, Cr, and Ti and was evaluated using multivariable comparison results are presented in Table 2.
All statistical analyses were performed using IBM SPSS were generally small, and 95% confidence intervals included the
USA), and a two-sided p-value < 0.05 was considered statistically composite Metal Burden Index, calculated as the mean of
comparisons was applied. type. These results are shown in Table 3.
Sex (male/female) 26 (52%)/24 (48%)
Marital status (married/single/divorced/widowed) 39 (78%)/3 (6%)/2 (4%)/6 (12%)
Living region (central/northern/southern/eastern/western) 22 (44%)/8 (16%)/4 (8%)/8 (16%)/9 (18%)
Work status (current/past/never) 12 (24%)/17 (34%)/21 (42%)
Total family income in Saudi riyals (SAR) (<5,000/5,000-10,000/> 10,000/refused or unknown) 8 (16%)/11 (22%)/22 (44%)/9 (18%)
Herbal remedies (yes/no) 8 (16%)/42 (84%)
Tumor location (proximal/distal/total colon) 15 (30%)/30 (60%)/5 (10%)
Depth of invasion (pT1/pT2–4) 1 (2%)/49 (98%)
Lympho-vascular invasion (present/absent) 21 (42%)/29 (58%)
Perineural invasion (present/absent) 13 (26%)/37 (74%)
Lymph node invasion (present/absent) 23 (46%)/27 (54%)
TABLE 2 Metal concentrations (µg/g wet weight) in paired non-cancerous and cancerous colon tissues (n = 50).

Methods (brief)

and the copyright owner(s) are credited were measured in paired colon tissue samples using ICP-MS. Global DNA
Despite experimental evidence linking metal exposure tissue located at least 10 cm from the tumor margin. Tissue samples
and circulating genotoxic and epigenetic biomarkers remain Peripheral venous blood samples were collected in EDTA tubes
(37). Clarifying this relationship is important for interpretating Colon tissue samples were prioritized for trace metal analysis.
and public health surveillance. measured in acid-digested colon tissue samples using inductively
Therefore, this study aimed to (i) characterize concentrations coupled plasma–mass spectrometry (ICP-MS; NexION R 2000,
commonly used biomarkers in environmental health research. to those of the study samples; these evaluations demonstrated
USA) in acid-cleaned, labeled Teflon digestion vessels. Tissue
Study design and participants samples were analyzed on a wet-weight basis, as frozen tissue was
This study included 50 Saudi adult patients (≥18 years) with mass of approximately 0.05 g was used for digestion. Samples were
& Research Center. Patients with rectal cancer were excluded, additional digestion step at 85 ◦ C for 1 hour. After cooling, the
enrollment. The study protocol was approved by the institutional was used for final sample preparation before ICP-MS analysis.
samples to correct for instrumental drift and matrix effects: iridium
Tissue and blood sample collection (193 Ir) for Pb, Cd, Hg, and As, and rhodium (103 Rh) for Cr and
Ti. Metal quantification was performed by ICP-MS, and diluent
Paired colon tissue specimens were collected from each signal intensities were subtracted from calibrators, quality control
participant at the time of surgical resection. Cancerous tissue samples, and patient specimens.
samples were obtained from the tumor mass, while non-cancerous Calibration curves ranged from 0.25 to 4 µg/L for Pb, Cd, Hg,

Implications

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Verification notes

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Update history

The five most recent substantive edits to this page, classified major (evidence or structure moved), correction (a published value or statement was wrong and has been fixed), or minor (narrative rewritten without changing the underlying evidence). Each description is derived from what the edit did to this page; the linked commit is the authoritative record, routine regeneration passes are excluded, and the full version history lives in git. When DOI minting comes online (see schema docs), each entry below will also link to a version-pinned DataCite DOI.

Commit	Date	Change	Description
b01ec52c	2026-08-04	major	2 sections added
d49e450f	2026-08-03	major	5 sections added; narrative text revised