Gene expression studies with immortalized cell lines are extremely weak evidence for anything that would happen in vivo.
This type of research has become very popular in the late 90's and early 2000's because it provided an easy and cheap vehicle for generating lots of (largely meaningless) publications in high profile journals using the emerging technology of gene expression arrays (aka DNA chips). Basically, anyone could pour something on some cells, throw them on a DNA chip, take a picture and publish that in Nature/Science, guaranteeing funding for the next meaningless grant proposal. This sort of research has its utility, but is hardly conclusive for real-world effects.
Moreover, immortalized cell lines require significant mutations to become immortal, essentially transforming them in pre-cancerous cells already. These mutations also significantly alters the cells biology to the point of making them completely different in form and function compared to the original tissues from which they were harvested - this has to be taken into account in any analysis of such experiments.
The present paper reports potentially valuable information regarding possible changes in gene expression of human cells exposed to media treated with ecig vapor. The cancer claim is, however, an abusive and alarmist stretch of these results, that, at face value, are: "263 differentially expressed genes." None of these genes were investigated or characterized. Moreover, the other snippet of results buried in that abstract, strongly refutes the cancer claim: "Treatment of H3mut-P53/KRAS cells with low nicotine ECIG- and TCIG-conditioned media did not further enhance the degree of invasion observed in the untreated group" and also "did not demonstrate toxic or anti-proliferative effects on the cells".
Major limitations of the study include:
- these cells are not normal human bronchial epithelial cells
- cells were not directly exposed to vapor (but some concocted medium "treated" with ecig vapor)
- it is unclear how the ecig vapor was obtained (possibly via the Pruebot method of overheating a coil in a dry carto to the point of melting solder?)
- the authors make alarmist and unsubstantiated claims about possible links to cancer.