Researchers in the U.S. say that preliminary research has suggested that nicotine can prevent chemotherapy drugs such as taxol from killing lung cancer cells.
They believe the discovery may help explain why lung cancer is so difficult to treat in smokers.
Their findings they say indicate that even nicotine supplements, such as patches or gum, may interfere with cancer therapy.
The team led by Srikumar Chellappan at the H. Lee Moffitt Cancer Center and Research Institute in Tampa, Florida say their findings support previous clinical studies which show that patients who continue to smoke have worse survival profiles than those who quit before treatment.
Srikumar Chellappan, an associate professor at the research Institute says the findings portray a simple message "if you have cancer, stay away from nicotine, either smoking, patches or gum".
Chellappan and colleagues, in their study tested the effect of nicotine on lung cancer cells exposed to three types of standard chemotherapy drugs, gemcitabine, cisplatin and taxol on several different batches of cells taken from lung cancer tumors.
The researchers discovered that the level of nicotine found in a typical smoker was enough to disrupt the chemotherapy drugs' ability to kill off the cancer cells.
Chellappan says the nicotine appears to boost the levels of two proteins that protect cancer cells.
The genes stopped a process called apoptosis, a kind of cell suicide, happening.
Although it is clear nicotine is a major factor in making tobacco addictive, its role in causing cancer is unclear as other substances that make up tobacco smoke are considered more dangerous, which is why doctors consider it acceptable to use nicotine-based gum and patches to help smokers quit.
Experts say the research is very preliminary, but recommend people receiving chemotherapy avoid taking in other poisons.
It is apparently quite common for people actually undergoing treatment for lung cancer to continue to smoke, especially if they have been told the cancer is not curable.
The study is published by the Proceedings of the National Academy of Sciences.