The Toxicologist - Society of Toxicology

this study we examined the effects of two agents that affect both CB1 and CB2 receptors,
namely WIN 55,212-2 (WIN), an aminoalkylindole derivative, which
mimics the effects of conventional cannabinoids, and cannabidiol (CBD), a major
constituent in the plant cannabis sativa. WIN and CBD inhibited colon (SW480
and RKO), pancreatic (L3.6pl) and prostate (LNCaP and PC3) cancer cell proliferation
and growth inhibitory IC50 values for 24 hr were in the range of 5.54-5.83
uM for WIN and 9.01-18.54 uM for CBD in these cell lines.Treatment of colon
and prostate cancer cell lines for 24 hr with 5-7.5 uM concentrations of WIN also
decreased specificity protein (Sp) transcription factors Sp1, Sp3 and Sp4 that are
normally overexpressed in cancer cells and tumors. This was accompanied by decreased
levels of Sp-dependent genes associated with cancer cell growth, survival
(survivin) and angiogenesis (VEGF). Colon (SW480), pancreatic (L3.6pl) and
prostate (PC3 and LNCaP) cancer cell proliferation was also inhibited after treatment
with 10-15 uM CBD for 24 hr. CBD-dependent effects on Sp and Sp-dependent
genes and inhibition of cell proliferation were observed at similar concentrations
of CBD. However, when cells were cotreated with WIN or CBD plus
specific CB1 and CB2 receptor antagonists downregulation of Sp transcription factors
was not reversed. Moreover, treatment with thiol antioxidants did not block
the effects of CB-dependent repression of Sp1, Sp3 or Sp4 and the mechanisms of
CB-Sp transcription factor interactions are currently being investigated.
141 THE URINARY BLADDER CARCINOGEN PROPOXUR
DOES NOT INDUCE GENOTOXIC EFFECTS IN THE
URINARY BLADDER OF WISTAR MALE RATS.
A. M. Jeffrey 1 , G. M. Williams 1 , M. J. Iatropoulos 1 , J. Duan 1 and G. Schmuck 2 .
1
Pathology, New York Medical College, Valhalla, NY and 2 Bayer Schering
Pharmacology AG, Wuppertal, Germany.
Propoxur (PPX) is a carbamate insecticide which induced bladder cancer in Wistar
rats when fed at 5000 ppm in Altromin 1321 diet (1321). PPX was studied for several
key events related to carcinogenicity in the urinary bladders (UBs) of Wistar
rats administered the compound for 28 days at 8000 ppm in Provini Kliba SA 3883
diet (3883), which is similar to the 1321 diet. o-Anisidine HCl (AH) was used as a
genotoxic UB carcinogenic comparator, and trisodium nitrilotriacetate (NTA) as an
epigenetic UB carcinogen comparator. For the untreated control and 3 test substance
groups (PPX, AH, NTA), 4 additional groups were fed 2% ammonium
chloride (AC) in the diet, to acidify the urine since 1321 is reported to increase urinary
pH. AC did acidify the urine, as expected, although the 3883 diet itself did
not increase pH values above 8. In the nucleotide 32P-postlabeling assay (NPL),
AH produced DNA adducts in the UB urothelium (UBU), whereas PPX and NTA
did not. In the alkaline comet assay, AH produced DNA strand breaks (DSBs),
whereas PPX and NTA did not. Assessment of UBU cell proliferation as measured
by immunohistochemistry of proliferating cell nuclear antigen, revealed that NTA
and NTA plus AC increased the replicating fraction (RF). Also AH plus AC increased
the RF of UBU, whereas PPX groups were not significantly different from
controls. Thus, the results reveal no evidence for DNA binding or DSBs in the
UBU by PPX, while confirming UBU DNA damage by AH and showing that
NTA does not damage DNA. Also there was no evidence for stimulation or inhibition
of DNA synthesis in the UBU by PPX.
142 OXIDATIVE DNA DAMAGE AND HUMAN
ESOPHAGEAL CANCER RISK IN HUAIAN, CHINA.
L. Xu 1 , L. Tang 1 , X. Wang 2 , Z. Wang 3 , G. Sun 4 , S. Wang 4 , X. Hu 5 and J. S.
Wang 1 . 1 Environmental Health Science, University of Georgia, Athens, GA,
2
University of Iowa, Iowa City, IA, 3 Indiana University, Indianapolis, IN,
4
Southeast University, Nanjing, China and 5 Chuzhou CDC, Huaian, China.
Oxidative DNA damage plays important role in carcinogenesis and 8-hydroxy-2’-
deoxyguanosine (8-OHdG), the most common oxidative DNA damage biomarker,
has been shown to associate with exposure to many environmental carcinogens and
formation of several cancer sites. However, its contributing role to human
esophageal cancer remains unclear. To investigate its potential role in esophageal
carcinogenesis, we conducted a population-based case-control study, with 188
esophageal squamous cell carcinoma (ESCC) cases and 524 age-, gender-, and residency-matched
healthy controls recruited from Huaian, China, a high risk area of
ESCC. Levels of 8-OHdG in morning urine was determined by solid-phase extraction
coupled with HPLC- electrochemical detection and adjusted by urinary creatinine.
DNA repair gene, hOGG1, is responsible for repairing oxidative DNA damage
and its single nucleotide polymorphism (Ser326Cys) was determined by
PCR/RFLP using DNA extracted from peripheral blood lymphocytes. The averaged
urinary 8-OHdG level in case group was 49.56 ± 235.66 μg/mg creatinine
(mean±SD; range: 1.28 – 3210.23 μg/mg creatinine), with a median level of 22.04
μg/mg creatinine. The averaged urinary 8-OHdG level in the control group was
23.30 ± 47.32 μg/mg creatinine (range: 0.71 – 817.22) with median level of 13.71
μg/mg creatinine. Levels of 8-OHdG in cases were significantly higher than those
in controls (p