Changes in LINE-1 methylation level in cancers during metastasis

Background: Significantly lower LINE-1 methylation levels have been observed in several cancers compared to their normal cell counterparts. It is of interest to note that this epigenetic phenomenon is rather common to cancers with multistage oncogenesis.

Objective: We compared LINE-1 methylation levels of cancer cells between the primary and matched metastatic sites.

Methods: COBRA method was used to determine LINE-1 methylation levels of tumor cells at the primary and matched metastatic sites in five malignancies (10 cases each of head and neck squamous carcinoma, papillary thyroid carcinoma, non-small cell lung cancer, invasive mammary ductal carcinoma, and colorectal adenocarcinoma). LINE-1 methylation levels between the primary and matched metastatic site were compared.

Results: Significantly lower LINE-1 methylation levels were observed at metastatic sites (as compared to primary sites) in head and neck squamous cell carcinoma (p = 0.002) and non-small cell lung cancer (p = 0.012).

Conclusion: In head, neck, and pulmonary cancers, significantly lower LINE-1 methylation levels were found at metastatic sites, as compared to the matched primary tumor. Further studies are warranted to determine whether this altered methylation is the result or the cause of cancer metastasis.