LINE-1 methylation patterns of different loci in normal and cancerous cells

This study evaluated methylation patterns of long interspersed nuclear element-1 (LINE-1) sequences from 17 loci in several cell types, including squamous cell cancer cell lines, normal oral epithelium (NOE), white blood cells and head and neck squamous cell cancers (HNSCC). Although sequences of each LINE-1 are homologous, LINE-1 methylation levels at each locus are different. Moreover, some loci demonstrate the different methylation levels between normal tissue types. Interestingly, in some chromosomal regions, wider ranges of LINE-1 methylation levels were observed. In cancerous cells, the methylation levels of most LINE-1 loci demonstrated a positive correlation with each other and with the genome-wide levels. Therefore, the loss of genome-wide methylation in cancerous cells occurs as a generalized process. However, different LINE-1 loci showed different incidences of HNSCC hypomethylation, which is a lower methylation level than NOE. Additionally, we report a closer direct association between two LINE-1s in different EPHA3 introns. Finally, hypermethylation of some LINE-1s can be found sporadically in cancer. In conclusion, even though the global hypomethylation process that occurs in cancerous cells can generally deplete LINE-1 methylation levels, LINE-1 methylation can be influenced differentially depending on where the particular sequences are located in the genome

Assessment of physicians’ awareness of MRONJ and related practices (<i>N</i> = 181).

Assessment of physicians’ awareness of MRONJ and related practices (N = 181).</p

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A serious adverse effect of antiresorptive drugs, which are widely used to treat osteoporosis, is medication-related osteonecrosis of the jaw (MRONJ). Physicians can reduce the risk of MRONJ by educating patients and emphasizing the importance of good oral health. However, limited information is available regarding physicians’ awareness and clinical practices associated with MRONJ. Hence, this study aimed to examine physicians’ awareness related to MRONJ and associated clinical practices. This study was a cross-sectional study conducted from December 2022 to February 2023. An online self-administered questionnaire was sent to physicians in Thailand who prescribed antiresorptive drugs for osteoporosis. Most respondents agreed that antiresorptive drugs might cause MRONJ (92.3%), poor oral health increased the risk of MRONJ (84%), and MRONJ is an important consideration in patients with osteoporosis (85%). Of the respondents, 48.1% and 15.5% always referred patients to dentists before and during antiresorptive therapy, respectively. Approximately 60% of physicians informed patients of the MRONJ risk before prescribing antiresorptive drugs, and 30% inquired about patients’ oral symptoms at the follow-up visit. Overall, 44% of physicians advised patients to receive oral health care; the most common reason for not advising this was that respondents did not consider themselves to be adequately knowledgeable to detect oral health problems. These findings indicate that while most physicians who prescribed antiresorptive drugs for osteoporosis were aware of and considered MRONJ in their practice, several took insufficient action to prevent it. This highlights the need to emphasize clinical practice guidelines and collaboration between physicians and dentists.</div

LINE-1 methylation patterns of different loci

in normal and cancerous cell

The influence of smoking on the epigenetic progression of multistep carcinogenesis.

<p>(A) Models of LINE-1 methylation patterns in oral mucosal cells of a NS, the oral mucosal cells of a CS and in cancer cells (HeLa) are shown. Although the overall methylation level did not change in the CS, some alterations in the methylation patterns were detected. While the numbers of ^mC^mC and ^uC^uC were increased, only one form of partial methylation, ^mC^uC, was decreased. Moreover, the addition of ^mC^mC and ^uC^uC correlated with the depletion of ^mC^uC. In contrast, a reduction in the overall methylation level was found in cancer cells. The numbers of ^mC^mC and ^mC^uC were significantly decreased, while the numbers of ^uC^uC were significantly increased. The numbers of ^uC^mC were slightly increased. (B) The smoking-induced hypomethylated loci could be derived from both classes of the partial methylation patterns and could result in genome instability and gene expression changes. However, the smoking-induced hypermethylated loci were from ^mC^uC only and, consequently, effected gene expression.</p

Multivariable analysis of factors associated with practice.

Multivariable analysis of factors associated with practice.</p

Reasons why physicians did not always refer patients to dentists.

Reasons why physicians did not always refer patients to dentists.</p

Patterns and Possible Roles of LINE-1 Methylation Changes in Smoke-Exposed Epithelia

<div><p>Tobacco smoking and reduced methylation of long interspersed element-1 (LINE-1) are crucial in oral carcinogenesis. 5′UTR of human LINE-1 sequence contains several CpG dinucleotides which are methylated in various proportions (0–100%). Methylation levels of many LINE-1s in cancer were reduced, hypomethylated. The hypomethylation of each LINE-1 locus can promote instability of genome and repress expression of a gene located on that same chromosome. This study investigated if cigarette smoking influences LINE-1 methylation of oral mucosal cells. The methylation of human LINE-1 in clinically normal oral mucosa of current smokers was compared to non-smokers. By using the combined bisulphite restriction analysis, each LINE-1 sequence was categorised into 4 patterns depending on the methylation status and location of the two 18-bp successive CpG from 5′ to 3′ including ^mC^mC, ^uC^uC, ^mC^uC and ^uC^mC. Of these, ^mC and ^uC represent methylated and unmethylated CpG, respectively. The DNA bisulphite sequence demonstrated that most CpGs of ^mC^mC and ^uC^uC were methylated and unmethylated, respectively. Nevertheless, some CpGs of each ^mC^uC or ^uC^mC allele were methylated. Imaging of the digestion products was used to generate %methylation value. No significant difference in the overall LINE-1 methylation level but the differences in percentages of some methylation patterns were discovered. The %^mC^mC and %^uC^uC increased, while the %^mC^uC decreased in current smokers (<em>p</em> = 0.002, 0.015, and <0.0001, respectively). Additionally, the lower %^mC^uC still persisted in persons who had stopped smoking for over 1 year (<em>p</em> = 0.001). The %^mC^uC also decreased in the higher pack-year smokers (<em>p</em> = 0.028). Smoking possibly altered ^mC^uC to ^mC^mC and ^uC^uC forms, and changes ^uC^mC to ^uC^uC forms. In conclusion, smoking changes methylation levels of partial methylated LINE-1s and increased the number of hypo- and hypermethylated loci. These hypomethylated LINE-1s may possess carcinogenesis potential. Moreover, LINE-1 methylation patterns may be useful for monitoring oral carcinogenesis in smokers.</p> </div

The percentages of LINE-1 products between never drinks and current drinkers.

a<p><i>t</i>-test was used to compare the percentage of LINE-1 products between never drink and currently drink of non-smokers.</p>b<p><i>t</i>-test was used to compare the percentage of LINE-1 products between never drink and currently drink of current smokers.</p