MedicalResearch.com Interview with:
Moon-shong Tang, PhD
Professor of Environmental Medicine, Pathology and Medicine
New York University Langone School of Medicine
Tuxedo Park, New York 10987
MedicalResearch.com: What is the background for this study?
Response: E-cigarettes (E-cigs) are designed to deliver the stimulant nicotine through aerosols, commonly referred as vapors. Nicotine is dissolved in organic solvents such as glycerin and propylene glycol. The nicotine is then aerosolized by controlled electric heating. E-cigs do not use tobacco leaves and E-cig smoke does not involve the burning process. Hence, E-cig smoke (ECS) contains only nicotine and the gas phase of the solvent. Because ECS contains neither carcinogens nor allergens or odors from the tobacco burning process, E-cigs have been promoted as an invention that can deliver a TS ‘high’ without TS negative effects. The population of E-cig users is rapidly rising, particularly in young adults. It has been estimated that 16% of high school students are E-cig smokers. Therefore, the health effects of E-cig smoke, particularly its carcinogenicity, deserve careful scrutiny.
MedicalResearch.com: What are the main findings?
Response: Our study has two hypotheses. One, since the majority of inhaled nicotine (70-80%) is rapidly metabolized into cotinine and both nicotine and cotinine are eventually excreted into urine, we assume the bladder is a main target of nicotine’s harmful effects. Two, although cotinine is relatively harmless, on the other hand, nicotine in bladder can be transformed into carcinogenic nitrosamines, NNN and NNK, if nitrosation, a process which occurs during tobacco curing, occurs. NNN and NNK carcinogenicity is generally believed via their metabolites, CH3NNOH and CH2O, to induce DNA damage. We tested these hypotheses by exposing mice to E-cig smoke for a period of time (12 weeks) and determining DNA damage in their bladder mucosa. We found that E-cig smoke induces two type of mutagenic DNA damage: cyclic 1,N2-propano-deoxyguanosine and O6-methyl-dG. We found that the same reactions can occur in human urothelial cells. Furthermore, nicotine and its metabolites can also inhibit DNA repair, enhance urothelial cells’ mutational susceptibility and tumorigenic transformation. These results strongly suggest E-cig smoke is a potential bladder carcinogen.
MedicalResearch.com: What should readers take away from your report?
Response: E-cigarette smoke will increase bladder cancer risk and perhaps cause cancer in other organs.
MedicalResearch.com: What recommendations do you have for future research as a result of this study?
Response: First and foremost is to conduct animal experiment to determine E-cigarette smoke carcinogenicity in the bladder and other organs, which could lead to the development of measures to intervene in the E-cigarette smoke induced carcinogenic processes.
Second, is to determine the effects of second hand E-cigarette smoke. Funding and demand for this type of research from governments and public research institutes is urgently needed.
MedicalResearch.com: Is there anything else you would like to add?
Response: Since no animal experiments have been done to demonstrate that E-cigarette smoke can induce cancer and no epidemiologic studies have been done to associate E-cigarette smoke with increased cancer incidence, the E-cigarette industry will continue promote E-cigarette as non-carcinogenic. Even though our results show unambiguously that E-cigarette smoke can induce carcinogenic events, such as induction of mutagenic DNA damage, inhibition of DNA repair and increase of mutational susceptibility and cell tumorigenic transformation, research on E-cigarette carcinogenesis in animal models is urgently needed. Establishing the carcinogenicity of E-cigarette smoke in animal models will dispel the unsubstantiated claim that E-cigarette smoke is safe.
No conflict of interest
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