Comparative assessment of HPHC yields in the Tobacco Heating System THS2.2 and commercial cigarettes.

There has been a sustained effort in recent years to develop products with the potential to present less risk compared with continued smoking as an alternative for adult smokers who would otherwise continue to smoke cigarettes. During the non-clinical assessment phase of such products, the chemical composition and toxicity of their aerosols are frequently compared to the chemical composition and toxicity of the smoke from a standard research cigarette - the 3R4F reference cigarette. In the present study, it is demonstrated that results of these analytical comparisons are similar when considering commercially available cigarette products worldwide.

Reduced toxicological activity of cigarette smoke by the addition of ammonia magnesium phosphate to the paper of an electrically heated cigarette: subchronic inhalation toxicology.

Cigarette smoke is a complex chemical mixture that causes a variety of diseases, such as lung cancer. With the electrically heated cigarette smoking system (EHCSS), temperatures are applied to the tobacco below those found in conventional cigarettes, resulting in less combustion, reduced yields of some smoke constituents, and decreased activity in some standard toxicological tests. The first generation of electrically heated cigarettes (EHC) also resulted in increased formaldehyde yields; therefore, a second generation of EHC was developed with ammonium magnesium phosphate (AMP) in the cigarette paper in part to address this increase.

A constitutively active dioxin/aryl hydrocarbon receptor promotes hepatocarcinogenesis in mice.

The dioxin/aryl hydrocarbon receptor (AhR) functions as a ligand-activated transcription factor regulating transcription of a battery of genes encoding enzymes involved in drug metabolism. Known ligands include polycyclic aromatic hydrocarbons, certain polychlorinated biphenyls, and the polyhalogenated dioxins including 2,3,7,8-tetrachlorodibenzo-p-dioxin. Both polyhalogenated biphenyls and 2,3,7,8-tetrachlorodibenzo-p-dioxin are potent promoters of rodent hepatocarcinogenesis in two-stage initiation-promotion experiments.

WY-14,643-mediated promotion of hepatocarcinogenesis in connexin32-wild-type and connexin32-null mice.

Connexin32 (Cx32) is the major gap junction forming protein in liver and lack of functional Cx32 enhances hepatocarcinogenesis. Many tumour-promoting agents block gap junctional intercellular communication, which may favour clonal expansion of neoplastic cells. We recently demonstrated that liver tumourigenesis is accelerated in Cx32-wild-type but not in Cx32-null mice by the model tumour promoter phenobarbital (PB).

Role of connexin32 and beta-catenin in tumor promotion in mouse liver.

Tumor promoters are nonmutagenic chemicals that increase the probability of cancer by accelerating the clonal expansion of cells transformed during tumor initiation. The molecular mechanisms underlying this process are only partly understood but interference with signaling pathways regulating cell division and/or cell death is likely to be important. Ras- and beta-Catenin-dependent signaling is important for both of these processes and ras and beta-catenin genes are known mutational targets in mouse hepatocarcinogenesis.

Selective pressure during tumor promotion by phenobarbital leads to clonal outgrowth of beta-catenin-mutated mouse liver tumors.

Tumor promoters are non-mutagenic chemicals which increase the probability of cancer by accelerating the clonal expansion of cells transformed during tumor initiation. Phenobarbital (PB) is an antiepileptic drug which promotes hepatocarcinogenesis in rodents when administered subsequent to an initiating carcinogen like diethylnitrosamine (DEN). Here we have investigated the prevalence and patterns of mutations in two genes, Ha-ras and beta-catenin, both known mutational targets in mouse hepatocarcinogenesis.

Lack of phenobarbital-mediated promotion of hepatocarcinogenesis in connexin32-null mice.

Connexin32 (Cx32) is the major gap junction forming protein in liver. We have recently shown that hepatocarcinogenesis is strongly enhanced in mice deficient in Cx32, demonstrating that lack of functional Cx32 accelerates liver tumorigenesis. Many tumor-promoting agents, including phenobarbital, block gap junctional intercellular communication in vitro, and it has been suggested that this effect is relevant for clonal expansion of neoplastic cells in vivo.

Hepatocarcinogenesis in female mice with mosaic expression of connexin32.

Mice deficient for connexin32 (Cx32), the major gap junction forming protein in liver, are highly susceptible to hepatocarcinogenesis. Because the Cx32 gene is located on the X-chromosome, heterozygous females show mosaicism with respect to Cx32 expression; this enables their use in studying the effect of Cx32-deficiency in a mixed Cx32-plus/Cx32-minus environment in vivo. Female C3H/He mice (Cx32(+/+)) were crossed with Cx32-deficient C57BL/129Sv males (Cx32(Y/-)) to yield F1 females heterozygous with respect to Cx32 (Cx32(+/-)).

The effect of connexin32 null mutation on hepatocarcinogenesis in different mouse strains.

Connexin32 (Cx32) is the major gap junctional protein in mouse liver. We have shown recently that the formation of liver tumours in Cx32-deficient mice is strongly increased in comparison with control wild-type mice, demonstrating that the deficiency in gap junctional communication has an enhancing effect on hepatocarcinogenesis. We have now compared the effect of Cx32 deficiency on liver carcinogenesis in two strains of mice with differing susceptibility to hepatocarcinogenesis.