The human papillomavirus (HPV) vaccination has significantly reduced the incidence of cervical cancer – but other HPV-positive cancers are on the rise. Anal cancer, in particular, is a problem because diagnosis is difficult and uncomfortable – both physically and psychologically. The current standard of care for diagnosis includes cytology, digital anal/rectal examination, high-resolution anoscopy, human papillomavirus testing, HPV16 genotyping, and staining of cells and biopsies for p16 and ki-67 biomarkers. Not only is this approach time-consuming and expensive (the algorithms are complex and need to be done as often as every few months), but it also allows many anal cancers to slip through. And, when they don’t, overtreatment (and its serious side effects) is a problem because doctors have no way to tell which anal lesions may become cancerous.
To alleviate the burden on both patients and health care providers, Attila Lorincz and his colleagues sought an answer in epigenetics. The group’s study (1) involved examining the epigenetics of anal biopsy specimens from 148 patients. They were expecting to find – if anything – a complex set of biomarkers requiring perhaps hundreds of genes. Instead, just two gene regions provided a remarkably accurate prediction of a patient’s risk of lesion progression. “We measure DNA methylation in certain regions of the HPV16 genome and in a human tumor suppressor gene, EPB41L3,” explains Lorincz. “Methylation in these DNA regions disrupts normal cellular controls and allows anal epithelial cells to grow unchecked. With time, the tissues become malignant. The two gene regions we use were carefully selected and work very well as biomarkers because they are closely related to the carcinogenesis mechanisms in anal epithelial cells.” The same gene regions are very good biomarkers of cervical and several other epithelial cancers – meaning that the mechanisms in these diseases may be the same or highly related. At the moment, the researchers are using their biomarkers to look more closely at other important epithelial cancers, such as oropharyngeal cancer. They are also looking into how far in advance the risk of anal and cervical cancers can be predicted – but the results of these studies will take time, as they require large numbers of patients and many years of follow-up up. Says Lorincz, “In the long term, we would like to see DNA methylation tests available routinely to men and women who may be at risk of anogenital cancers.”
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References
- AT Lorincz et al., “Methylation of HPV and a tumor suppressor gene reveals anal cancer and precursor lesions”, Oncotarget, [Epub ahead of print] (2017). PMID: 28591708.