Triplet Repeat Expansion Generated by DNA Slippage Is Suppressed by Human Flap Endonuclease 1

Human flap endonuclease 1 (h-FEN1) mutations have dramatic effects on repeat instability. Current models for repeat expansion predict that h-FEN1 protein prevents mutations by removing 5'-flaps generated at ends of Okazaki fragments by strand displacement synthesis. The models propose that hairpin formations within flaps containing repeats enable them to escape h-FEN1 cleavage. Friedreich's ataxia is caused by expansion mutations in a d(GAA)n repeat tract. Single-stranded d(GAA)n repeat tracts, however, do not form stable hairpins until the repeat tracts are quite long. Therefore, to understand how d(GAA)n repeat expansions survive h-FEN1 activity, we determined the effects of h-FEN1 on d(GAA)n repeat expansion during replication of a d(TTC)n repeat template. Replication initiated within the repeat tract generated significant expansion that was suppressed by the addition of h-FEN1 at the start of replication. The ability of h-FEN1 to suppress expansion implies that DNA slippage generates a 5'-flap in the nascent strand independent of strand displacement synthesis by an upstream polymerase. Delaying the addition of h-FEN1 to the replication reaction abolished the ability of h-FEN1 ability to suppress d(GAA)n repeat expansion products of all sizes, including sizes unable to hairpin. Use of model substrates demonstrated that h-FEN1 cleaves d(GAA)n 5'-flaps joined to double-stranded nonrepeat sequences but not those joined to double-stranded repeat tracts. The results provide evidence that, given the opportunity, short d(GAA)n repeat expansion products rearrange from 5'-flaps to stable internal loops inside the repeat tract. Long expansion products are predicted to form hairpinned flaps and internal loops. Once formed, these DNA conformations resist h-FEN1. The biological implications of the results are discussed

Association of Inventory to Measure and Assess imaGe Disturbance - Head and Neck Scores With Clinically Meaningful Body Image-Related Distress Among Head and Neck Cancer Survivors

Objective: The Inventory to Measure and Assess imaGe disturbance - Head and Neck (IMAGE-HN) is a validated patient-reported outcome measure of head and neck cancer-related body image-related distress (BID). However, the IMAGE-HN score corresponding to clinically relevant BID is unknown. The study objective is to determine the IMAGE-HN cutoff score that identifies head and neck cancer patients with clinically relevant BID. Methods: We conducted a cross-sectional study at six academic medical centers. Individuals ≥18 years old with a history of head and neck cancer treated with definitive intent were included. The primary outcome measure was the IMAGE-HN. A Receiver Operating Characteristic curve analysis was performed to identify the IMAGE-HN score that maximized sensitivity and specificity relative to a Body Image Scale score of ≥10 (which indicates clinically relevant BID in a general oncology population). To confirm the validity of the IMAGE-HN cutoff score, we compared the severity of depressive [Patient Health Questionnaire-9 (PHQ-9)] and anxiety symptoms [Generalized Anxiety Disorder-7 (GAD-7)], and quality of life [University of Washington-QOL (UW-QOL)] in patients with IMAGE-HN scores above and below the cutoff. Results: Of the 250 patients, 70.4% were male and the mean age was 62.3 years. An IMAGE-HN score of ≥22 was the optimal cutoff score relative to a Body Image Scale score of ≥10 and represents a clinically relevant level of head and neck cancer-related BID. Relative to those with an IMAGE-HN score of \u3c22, patients with IMAGE-HN scores of ≥22 had a clinically meaningful increase in symptoms of depression (mean PHQ-9 score difference = 5.8) and anxiety (mean GAD-7 score difference = 4.1) as well as worse physical (mean UW-QOL score difference = 18.9) and social-emotional QOL (mean UW-QOL score difference = 21.5). Using an IMAGE-HN cutoff score ≥22, 28% of patients had clinically relevant BID. Conclusion: An IMAGE-HN score of ≥22 identifies patients with clinically relevant head and neck cancer-related BID. This score may be used to detect patients who could benefit from strategies to manage their distress, select patients for studies evaluating interventions to manage head and neck cancer-related BID, and improve our understanding of the underlying epidemiology of the disorder

Factors Associated With Risk of Body Image-Related Distress in Patients With Head and Neck Cancer

Importance: Body image-related distress (BID) is common among head and neck cancer (HNC) survivors and associated with significant morbidity. Risk factors for HNC-related BID remain poorly characterized because prior research has used outcome measures that fail to fully capture BID as experienced by HNC survivors. Objective: To assess the association of demographic and oncologic characteristics with HNC-related BID using the Inventory to Measure and Assess imaGe disturbancE-Head & Neck (IMAGE-HN), a validated, multidomain, patient-reported outcome measure of HNC-related BID. Design, Setting, and Participants: This cross-sectional study assessed 301 adult survivors of surgically managed HNC at 4 academic medical centers. Main Outcomes and Measures: The primary outcome measure was IMAGE-HN scores, for which higher scores reflect more severe HNC-related BID. Multivariable linear regression analyses were performed to evaluate the association of patient characteristics with IMAGE-HN global and 4 subdomain (other-oriented appearance concerns, personal dissatisfaction with appearance, distress with functional impairments, and social avoidance) scores. Results: Of the 301 participants (212 [70.4%] male; mean [SD] age, 65.3 [11.7] years), 181 (60.1%) underwent free flap reconstruction. Graduation from college (β = -9.6; 95% CI, -17.5 to -1.7) or graduate school (β = -12.6; 95% CI, -21.2 to -3.8) was associated with lower IMAGE-HN social avoidance scores compared with less than a high school education. Compared with paid work, unemployment was associated with higher IMAGE-HN other-oriented appearance (β = 10.7; 95% CI, 2.0-19.3), personal dissatisfaction with appearance (β = 12.5; 95% CI, 1.2-23.7), and global (β = 8.0; 95% CI, 0.6-15.4) scores. Compared with no reconstruction, free flap reconstruction was associated with higher IMAGE-HN global scores (β = 11.5; 95% CI, 7.9-15.0) and all subdomain scores (other-oriented appearance: β = 13.1; 95% CI, 8.6-17.6; personal dissatisfaction with appearance: β = 15.4; 95% CI, 10.0-20.7; distress with functional impairment: β = 12.8; 95% CI, 8.1-17.4; and social avoidance and isolation: β = 10.2; 95% CI, 5.8-14.6). Higher IMAGE-HN distress with functional impairment scores were found in those who received surgery and adjuvant radiation (β = 7.8; 95% CI, 2.9-12.7) or chemoradiotherapy (β = 6.5; 95% CI, 1.8-11.3) compared with surgery alone. The multivariable regression model accounted for a modest proportion of variance in IMAGE-HN global (R2 = 0.18) and subdomain scores (R2 = 0.20 for other-oriented appearance, 0.14 for personal dissatisfaction with appearance, 0.21 for distress with functional impairment, and 0.13 for social avoidance and isolation). Conclusions and Relevance: In this cross-sectional study, factors associated with risk of HNC-related BID included free flap reconstruction, lower educational attainment, unemployment, and multiple treatment modalities. These characteristics explain a modest proportion of variance in IMAGE-HN scores, suggesting that other characteristics may be the major risk factors for HNC-related BID and should be explored in future studies