A recent study from investigators at Chongqing University in China explored the involvement of three viruses in the progression of pituitary adenomas (PA). The authors suggest that the HPV-16 and HHV-6 viruses activate the TLR3/ NF-kB signaling pathway which in turn contributes to the progression and proliferation of invasive pituitary adenomas. There was no evidence that HSV-1, on the other hand, played any role in tumor progression.
Sixty patients were included in this study: 30 with invasive PA and 30 with noninvasive PA. HPV-16 DNA was found in 70% of invasive PA samples and only in 26.67% of non-invasive samples. Similarly, HHV-6B DNA was detected in 53.33% of invasive samples, while it was only found in 30% of non-invasive PA samples.
The researchers also measured the mRNA and protein expression levels of TLR3, which were found to be significantly higher in invasive PA than in noninvasive PA. Furthermore, NF-kB-regulated genes for the inflammatory cytokines MMP9, IL-6, IL-1b, and TNFa were found to be up-regulated along with TLR3 activation.
Pituitary adenomas are neoplasms in the anterior pituitary and are associated with conditions such as acromegaly (an overproduction of growth hormone), Cushing’s syndrome (excessive production of cortisol), and diabetes insipidus (a reduction in the production of antidiuretic hormone). Approximately 35% of these tumors are invasive, meaning that operations are usually necessary to prevent the tumor from invading the brain.
It has been suggested that HHV-6 may play a role in the development of other neoplasms including the nodular sclerosis subset of Hodgkin’s lymphoma (Hudnall 2012) and gliomas (Chi 2012). The inherited HHV-6 virus, or chromosomally integrated HHV-6 (ciHHV-6) was also found to be overly represented in pediatric patients with adrenocortical tumors.
For more information, read the full paper.