RNA isolation using transcription analyses

Subsequent experiments were carried out to find out whether the early carcinogen-induced gene expression changes were only temporary or whether the changes actually led to the development of solid tumours. The exposure of Eker rats to AA and OTA for between three and six months allowed the researchers to assess the number of preneoplastic lesions formed. Dr. Stemmer used transcription analyses to find out how these preneoplastic lesions, which occurred in higher numbers in carcinogen-treated animals than in control animals, differ from healthy tissue and what effects AA and OTA have on the formation of preneoplastic lesions. "Using ‘laser capture microdissection' we were able to identify the microscopically small lesions under the microscope, cut them out using a computer-controlled laser beam and catapult them into reaction vessels. We succeeded in isolating RNA from these tiny tissue samples and this RNA was then used for microarray transcriptome analyses," said the biologist explaining the procedure. The researchers were able to verify individual signalling pathways using immunohistochemical staining. Traditional long-term studies are carried out under standardised conditions using rodents. However, these studies do not take into account the effect of risk factors such as adiposity and being overweight, conditions which are known to promote the development of tumours in humans. In a third step, Dr. Stemmer studied the effect of adiposity and high-calorie food on the development of early stages of renal carcinoma. The researchers were mainly interested in finding out whether high body adiposity per se or a high-calorie diet was the cause of increased renal cancer risk. "In collaboration with Prof. Daniel Dietrich's team at the University of Konstanz and Prof. Matthias Tschöp's and Prof. Paul Pfluger's groups at the Metabolic Diseases Institute at the University of Cincinnati, we were able to collect very promising data. Our results were awarded the Journal of Clinical Investigation poster prize at a recent scientific meeting," said the scientist.

Early processes provide information about mechanisms of action

All in all, Dr. Stemmer's research has led to some surprising results. The investigations showed that early gene expression changes after short-term exposure to carcinogens were predictive for the incidence and number of preneoplastic lesions. In addition, gene expression profiling enables the differentiation between genotoxic and non-genotoxic substances. It is worth noting that the altered gene expression profiles were very similar to spontaneous and substance-induced lesions. "It appears that early tumour stages no longer respond to long-term exposure to toxins," Dr. Stemmer explains.

Another interesting discovery was the fact that although aristolochic acid (AA) and mycotoxin ochratoxin A (OTA) led to early preneoplastic lesions, the surrounding kidney tissue seems to adapt to the toxic substances during long-term exposure: "Hardly any effects could be observed in healthy kidney tissue after a six-month exposure to the toxic substances."

It is the early processes in particular that can provide information about the carcinogenic mechanisms of action of a certain substance. "We assume that the application of new and more sensitive detection technologies such as microarrays will be able to considerably reduce the duration of long-term cancerogenesis studies and the number of experimental animals used for this purpose," said Dr. Stemmer highlighting the significance of her investigations. In July 2010, Dr. Stemmer was awarded the Nycomed Junior Investigator Award in recognition of her achievements.

Validation of new test systems and improved cancer therapies resulting from the collaboration between science and industry

In April 2010, the University of Konstanz offered Kerstin Stemmer the opportunity to spend a two-year research period at the University of Cincinnati Metabolic Diseases Institute. In 2012, Dr. Stemmer will return to the University of Konstanz and set up her own junior research group.

Dr. Stemmer's research at the Metabolic Diseases Institute focuses on the effects of adiposity and diabetes on elevated cancer risk. "Using state-of-the-art imaging methods such as bioluminescence and CT scanning, we are currently comparing the growth of tumours in slim and overweight rats and mice," said Dr. Stemmer describing her current research. "We are extremely interested in clarifying whether the therapeutic outcome of currently used cancer drugs differs between adipose and normal-weight patients." In addition, Dr. Stemmer is working with Ethicon Endo-Surgery, the global leader in the development and marketing of medical products for bariatic surgery. The partners are focusing on clarifying whether surgical methods to reduce adiposity such as gastric banding, gastric bypass or sleeve gastrectomy have an effect on the remission of solid tumours and are able to improve current cancer therapies.

"Generally speaking, there is huge potential for close collaboration between universities and industry in issues involving protection against carcinogenic substances and cancer," said Dr. Stemmer going on to add "I did my doctoral thesis in collaboration with Bayer-Scherin AG's Department of Special Toxicology in Wuppertal". The scientist believes that she will be able to expand her research in collaboration with industry and that microarray-based short-term investigations will some time in the future be validated as test systems. In addition, the in-depth understanding of cancer development in adiopose and normal-weight people will help to improve cancer therapies.