Revisiting the Posterior Approach for Cervical Radiculopathy Utilizing Endoscopic Techniques: A Favorable Short-Term Outcome and Cost Comparison With Anterior Cervical Discectomy and Fusion.

BACKGROUND: Cervical radiculopathy is a spine ailment frequently requiring surgical decompression via anterior cervical discectomy and fusion (ACDF) or posterior foraminotomy/discectomy. While endoscopic posterior foraminotomy/discectomy is gaining popularity, its financial impact remains understudied despite equivalent randomized long-term outcomes to ACDF. In a cohort of patients undergoing ACDF vs endoscopic posterior cervical foraminotomy/discectomy, we sought to compare the total cost of the surgical episode while confirming an equivalent safety profile and perioperative outcomes. METHODS: A single-center retrospective cohort study of patients with unilateral cervical radiculopathy undergoing ACDF or endoscopic cervical foraminotomy between 2018 and 2023 was undertaken. Primary outcomes included the total cost of care for the initial surgical episode (not charges or reimbursement). Perioperative variables and neurological recovery were recorded. Multivariable analysis tested age, body mass index, race, gender, insurance type, operative time, and length of stay. RESULTS: A total of 38 ACDF and 17 endoscopic foraminotomy/discectomy operations were performed. All patients underwent single-level surgery except for 2 two-level endoscopic decompressions. No differences were found in baseline characteristics and symptom length except for younger age (46.8 ± 9.4 vs 57.6 ± 10.3, P = 0.002) and more smokers (18.4% vs 11.8%, P = 0.043) in the ACDF group. Actual hospital costs for the episode of surgical care were markedly higher in the ACDF cohort (mean ±95% CI; $27,782 ± $2011 vs $10,103 ± $720, P < 0.001) driven by the ACDF approach (ß = $17,723, P < 0.001) on multivariable analysis. On sensitivity analysis, ACDF was never cost-efficient compared with endoscopic foraminotomy, and endoscopic failure rates of 64% were required for break-even cost. ACDF was associated with significantly longer operative time (167.7 ± 22.0 vs 142.7 ± 27.4 minutes, P < 0.001) and length of stay (1.1 ± 0.5 vs 0.1 ± 0.2 days, P < 0.001). No significant difference was found regarding 90-day neurological improvement, readmission, reoperation, or complications. CONCLUSION: Compared with patients treated with a single-level ACDF for unilateral cervical radiculopathy, endoscopic posterior cervical foraminotomy/discectomy can achieve a similar safety profile, pain relief, and neurological recovery at considerably less cost. These findings may help patients and surgeons revisit offering the posterior cervical foraminotomy/discectomy utilizing endoscopic techniques. CLINICAL RELEVANCE: Endoscopic posterior cervical foraminotomy/discectomy offers comparable safety, pain relief, and neurological recovery to traditional methods but at a significantly lower cost.

Open Versus Endoscopic Approach for Thoracic Disk Herniations: Equivalent Short-Term Outcomes With Significantly Different Costs.

BACKGROUND AND OBJECTIVES: Open thoracic diskectomy often requires significant bone resection and fusion, whereas an endoscopic thoracic diskectomy offers a less invasive alternative. Therefore, we sought to compare one-level open vs endoscopic thoracic diskectomy regarding (1) perioperative outcomes, (2) neurological recovery, and (3) total cost. METHODS: A single-center, retrospective, cohort study using prospectively collected data of patients undergoing one-level thoracic diskectomy was undertaken from 2018 to 2023. The primary exposure variable was open vs endoscopic. The primary outcome was perioperative outcomes and neurological recovery. Secondary outcomes were total cost of care. Multivariable regression analysis controlled for age, body mass index, sex, symptom onset, disk characteristics, operative time, and length of stay. RESULTS: Of 29 patients undergoing thoracic diskectomy, 17 were open and 12 were endoscopic. Preoperative demographics, symptoms, and radiographic findings were comparable between the cohorts. Perioperatively, open surgery had significantly higher mean length of stay (4.9 ± 1.5 vs 0.0 ± 0.0 days, P < .001), median (IQR) longer operative time (342.8 [68.4] vs 141.5 [36] minutes, P < .001), and more blood loss (350 [390] vs 6.5 [20] mL; P < .001). 16 (94%) open patients required fusion vs 0 endoscopic (P < .001). Postoperative opioid use (P = .119), readmission (P = .665), reoperation (P = .553), and rate of neurological improvement (P > .999) were similar between the 2 groups. Financially, open surgical median costs were 7x higher than endoscopic ($59 792 [$16 118] vs $8128 [$1848]; P < .001), driven by length of stay (ß = $2261/night, P < .001), open surgery (ß = $24 106, P < .001), and number of pedicle screws (ß = $1829/screw, P = .002) on multivariable analysis. On sensitivity analysis, open surgery was never cost-efficient against endoscopic surgery and excess endoscopic revision rates of 86% above open revision rates were required for break-even costs between the surgical approaches. CONCLUSION: Endoscopic thoracic diskectomy was associated with decreased length of stay, operative time, blood loss, and total cost compared with the open approach, with similar neurological outcomes. These findings may help patients and surgeons seek endoscopic approach as a less morbid and less costly alternative.

Obstacles to receiving postoperative radiation therapy following separation surgery for metastatic spine disease.

OBJECTIVE: Obtaining timely postoperative radiotherapy (RT) following separation surgery is critical to avoid local recurrence of disease yet can be a challenge due to scheduling conflicts, insurance denials, and travel arrangements. In patients undergoing metastatic spine surgery for spinal cord compression, the authors sought to: 1) report the rate of postoperative RT, 2) describe reasons for patients not receiving postoperative RT, and 3) investigate factors that may predict whether a patient receives postoperative RT. METHODS: A single-center retrospective case series was undertaken of all patients who underwent metastatic spine surgery for extradural disease between January 2010 and January 2021. Inclusion criteria were patients with intermediate or radioresistant tumors with evidence of spinal cord compression who underwent surgery. The primary outcome was the occurrence of RT within 3 months following surgery. Multivariable logistic regression analysis was performed controlling for age, BMI, race, total number of decompressed levels, tumor size, other organ metastasis, and preoperative RT or chemotherapy to predict patients receiving postoperative RT. RESULTS: Of 239 patients undergoing spine surgery for metastatic disease, 113 (47.3%) received postoperative RT while 126 (52.7%) did not. In the postoperative RT group, 24 (21.2%) received stereotactic body radiation therapy while 89 (78.8%) received conventional external-beam radiation therapy. The most common reasons for patients not receiving postoperative RT included death or transfer to hospice (31.0%), RT not being recommended by radiation oncology (30.2%), and loss to follow-up (23.8%). On critical review with the radiation oncology department, the authors estimated that 101 of 126 (80.2%) patients who did not receive postoperative RT were potential candidates for postoperative RT. Patients who received postoperative RT had more documented inpatient (48.7% vs 32.5%, p < 0.001) and outpatient (100.0% vs 65.1%, p < 0.001) radiation oncology consultations than those who did not. Additionally, patients who received postoperative RT had a higher rate of postoperative chemotherapy (53.1% vs 25.4%, p < 0.001), while patients who did not receive postoperative RT had a higher rate of preoperative RT (7.1% vs 31.0%, p < 0.001). Multivariable analysis confirmed that patients who received preoperative RT had lower odds of undergoing postoperative RT (OR 0.14, 95% CI 0.06-0.34; p < 0.001), and patients who underwent postoperative chemotherapy had higher odds of undergoing postoperative RT (OR 3.83, 95% CI 2.05-7.17; p < 0.001). CONCLUSIONS: In the current study reflecting real-world care of patients with metastatic spine disease after undergoing separation surgery, 47% of patients did not receive postoperative RT, and 80% of those patients were potential candidates for postoperative RT. Radiation oncology consultation and postoperative chemotherapy were significantly associated with receiving postoperative RT, whereas preoperative RT was significantly associated with not receiving postoperative RT. The lack of timely postoperative RT highlights a potential gap in metastatic spine tumor care and underscores the necessity for prompt radiation oncology consultation and effective planning.

Stopping at C2 Versus C3/4 in Elective Posterior Cervical Decompression and Fusion: A 5-Year Follow-up Study.

STUDY DESIGN: This is a retrospective cohort study. OBJECTIVE: In patients undergoing elective posterior cervical laminectomy and fusion (PCLF) with a minimum of 5-year follow-up, we sought to compare reoperation rates between patients with an upper instrumented vertebra (UIV) of C2 versus C3/4. SUMMARY OF BACKGROUND DATA: The long-term outcomes of choosing between C2 versus C3/4 as the UIV in PCLF remain unclear. METHODS: A single-institution, retrospective cohort study from a prospective registry was conducted of patients undergoing elective, degenerative PCLF from December 2010 to June 2018. The primary exposure was UIV of C2 versus C3/4. The primary outcome was reoperation. Multivariable logistic regression controlled for age, smoking, diabetes, and fusion to the thoracic spine. RESULTS: Of the 68 patients who underwent PCLF with 5-year follow-up, 27(39.7%) had a UIV of C2, and 41(60.3%) had a UIV of either C3/4. Groups had similar duration of symptoms (P=0.743), comorbidities (P>0.999), and rates of instrumentation to the thoracic spine (70.4% vs. 53.7%, P=0.210). The C2 group had significantly longer operative time (231.8±65.9 vs. 181.6±44.1 mins, P<0.001) and more fused segments (5.9±1.8 vs. 4.2±0.9, P<0.001). Reoperation rate was lower in the C2 group compared with C3/4 (7.4% vs. 19.5%), though this did not reach statistical significance (P=0.294). Multivariable logistic regression showed increased odds of reoperation for the C3/4 group compared with the C2 group (OR=3.29, 95%CI=0.59-18.11, P=0.170), though statistical significance was not reached. Similarly, the C2 group had a lower rate of instrumentation failure (7.4% vs. 12.2%, P=0.694) and adjacent segment disease/disk herniation (0% vs. 7.3%, P=0.271), though neither trend attained statistical significance. CONCLUSIONS: Patients with a UIV of C2 had less than half the number of reoperations and less adjacent segment disease, though neither trend was statistically significant. Despite a lack of statistical significance, whether a clinically meaningful difference exists between UIV of C2 versus C3/4 should be validated in larger samples with long-term follow-up. LEVEL OF EVIDENCE: Level-3.

Racial and Socioeconomic Disparities in Laminoplasty Versus Laminectomy With Fusion in Patients With Cervical Spondylosis.

STUDY DESIGN: A retrospective cohort study using prospectively collected data. OBJECTIVE: The aim of this study was to investigate preoperative differences in racial and socioeconomic factors in patients undergoing laminoplasty (LP) versus laminectomy and fusion (LF) for degenerative cervical myelopathy (DCM). SUMMARY OF BACKGROUND DATA: DCM is prevalent in the United States, requiring surgical intervention to prevent neurological degeneration. While LF is utilized more frequently, LP is an emerging alternative. Previous studies have demonstrated similar neurological outcomes for both procedures. However, treatment selection is primarily at the discretion of the surgeon and may be influenced by social determinants of health that impact surgical outcomes. MATERIALS AND METHODS: The Quality Outcome Database (QOD), a national spine registry, was queried for adult patients who underwent either LP or LF for the management of DCM. Covariates associated with socioeconomic status, pain and disability, and demographic and medical history were collected. Multivariate logistic regression was performed to assess patient factors associated with undergoing LP versus LF. RESULTS: Of 1673 DCM patients, 157 (9.4%) underwent LP and 1516 (90.6%) underwent LF. A significantly greater proportion of LP patients had private insurance (P<0.001), a greater than high school level education (P<0.001), were employed (P<0.001), and underwent primary surgery (P<0.001). LP patients reported significantly lower baseline neck/arm pain and Neck Disability Index (P<0.001). In the multivariate regression model, lower baseline neck pain [odds ratio (OR)=0.915, P=0.001], identifying as non-Caucasian (OR=2.082, P<0.032), being employed (OR=1.592, P=0.023), and having a greater than high school level education (OR=1.845, P<0.001) were associated with undergoing LP rather than LF. CONCLUSIONS: In DCM patients undergoing surgery, factors associated with patients undergoing LP versus LF included lower baseline neck pain, non-Caucasian race, higher education, and employment. While symptomatology may influence the decision to choose LP over LF, there may also be socioeconomic factors at play. The trend of more educated and employed patients undergoing LP warrants further investigation.

Efficacy and Safety of the Ultrasonic Bone Scalpel in Lumbar Laminectomies.

Introduction: Despite recent advances in applied instruments and surgical techniques, the incidence of iatrogenic durotomies caused by traditional techniques remains significant. The ultrasonic bone scalpel (UBS) has been shown to improve speed and reduce complications in laminectomies in the cervical and thoracic spine when compared to traditional methods utilizing high-speed burr, punch forceps, or rongeurs. Thus, in this study, we aim to evaluate whether the use of the UBS in the lumbar spine would result in equivalent safety, efficacy, and patient-reported outcomes (PROs) improvement when compared to traditional methods of laminectomy. Methods: Data from a prospectively collected, single-institution registry was queried between January 1, 2019 and September 1, 2021 for patients with a primary diagnosis of lumbar stenosis who received a laminectomy (with or without fusion) using traditional methods or UBS method. Outcomes included 3-month and 12-month values for all PROs Measurement Information System (PROMIS) subdomains, Numerical Rating Scale (NRS) pain score, Oswestry Disability Index (ODI) percentage, Patient Health Questionnaire 9 (PHQ-9) score, operative complications, reoperations, and readmissions. Covariates selected for matching included age, operation type, and number of levels. A variety of statistical tests were utilized. Results: As per our findings, 2:1 propensity matching resulted in 64 "traditional group" patients and 32 "UBS group" patients. Post-match analysis found no differences between the traditional and UBS groups for demographic and baseline measures except for race and ethnicity. For the matched sample, no differences were noted in PROs, reoperations, or readmissions. There was a significant difference in rates of durotomies between the traditional and UBS groups (12.5% vs. 0.0%, p=0.049). Conclusions: Results showed the high-frequency oscillation technology implemented by the UBS helps to decrease the rate of injury to the dura, thus reducing the overall incidence of iatrogenic durotomies. We believe these data provide valuable information to surgeons and patients about the safety and efficacy of the UBS in performing lumbar laminectomies.

The Impact of the COVID-19 Pandemic on the Presentation of Patients With Spinal Metastases.

STUDY DESIGN: Retrospective review. OBJECTIVE: The aim was to determine if preoperative spinal instability neoplastic scores (SINSs) and Tokuhashi prognostication scores differed in patients receiving surgical care before and during the coronavirus disease-2019 (COVID-19) pandemic. SUMMARY OF BACKGROUND DATA: The COVID-19 pandemic has caused delays in scheduling nonemergent surgeries. Delay in presentation and/or surgical treatment for oncology patients with metastatic spinal disease could result in progression of the disease, which can complicate surgical care and worsen patient outcomes. MATERIALS AND METHODS: Retrospective review of electronic medical records between March 1, 2019 and March 1, 2021 at a tertiary medical center was performed to identify patients who underwent surgery for metastatic spine disease. Primary spinal tumors were excluded. Patients were separated into two groups base on their surgery date: before the COVID-19 pandemic (March 1, 2019-February 29, 2020) and during the COVID-19 pandemic (March 1, 2020-March 1, 2021). Primary outcomes included SINS and Tokuhashi scores. A variety of statistical tests were performed to compare the groups. RESULTS: Fifty-two patients who underwent surgery before the COVID-19 pandemic were compared to 41 patients who underwent surgery during the COVID-19 pandemic. There was a significant difference between the before and during groups with respect to SINS (9.31±2.39 vs . 11.00±2.74, P =0.002) and Tokuhashi scores (9.27±2.35 vs . 7.88±2.85, P =0.012). Linear regression demonstrated time of surgery (before or during COVID-19 restrictions) was a significant predictor of SINS (ß=1.55, 95% CI: 0.42-2.62, P =0.005) and Tokuhashi scores (ß=-1.41, 95% CI: -2.49 to -0.34, P =0.010). CONCLUSIONS: Patients with metastatic spinal disease who underwent surgery during the COVID-19 pandemic had higher SINS, lower Tokuhashi scores and similar Skeletal Oncology Research Group scores compared to patients who underwent surgery before the pandemic. This suggests the pandemic has impacted the instability of disease at presentation in patients with spinal metastases, but has not impacted surgical prognosis, as there were no differences in Skeletal Oncology Research Group scores and the difference in Tokuhashi scores is most likely not clinically significant.

National Trends and Correlates of Dysphagia After Anterior Cervical Discectomy and Fusion Surgery.

OBJECTIVE: Anterior cervical discectomy and fusion (ACDF) is the most common performed surgery in the cervical spine. Dysphagia is one of the most frequent complications following ACDF. Several studies have identified certain demographic and perioperative risk factors associated with increased dysphagia rates, but few have reported recent trends. Our study aims to report current trends and factors associated with the development of inpatient postoperative dysphagia after ACDF. METHODS: The National Inpatient Sample was evaluated from 2004 to 2014 and discharges with International Classification of Diseases procedure codes indicating ACDF were selected. Time trend series plots were created for the yearly treatment trends for each fusion level by dysphagia outcome. Separate univariable followed by multivariable logistic regression analyses were performed to evaluate predictors of dysphagia. RESULTS: A total of 1,212,475 ACDFs were identified in which 3.3% experienced postoperative dysphagia. A significant increase in annual dysphagia rates was observed from 2004-2014. Frailty, intraoperative neuromonitoring, 4 or more level fusions, African American race, fluid/electrolyte disorders, blood loss, and coagulopathy were all identified as significant independent risk factors for the development of postoperative dysphagia following ACDF. CONCLUSION: Postoperative dysphagia is a well-known postsurgical complication associated with ACDF. Our cohort showed a significant increase in the annual dysphagia rates independent of levels fused. We identified several risk factors associated with the development of postoperative dysphagia after ACDF.

Effects of Body Mass Index on Perioperative Outcomes in Patients Undergoing Anterior Cervical Discectomy and Fusion Surgery.

OBJECTIVE: Obesity has become a public health crisis and continues to be on the rise. An elevated body mass index has been linked to higher rates of spinal degenerative disease requiring surgical intervention. Limited studies exist that evaluate the effects of obesity on perioperative complications in patients undergoing anterior cervical discectomy and fusion (ACDF). Our study aims to determine the incidence of obesity in the ACDF population and the effects it may have on postoperative inpatient complications. METHODS: The National Inpatient Sample was evaluated from 2004 to 2014 and discharges with International Classification of Diseases procedure codes indicating ACDF were identified. This cohort was stratified into patients with diagnosis codes indicating obesity. Separate univariable followed by multivariable logistic regression analysis were performed for the likelihood of perioperative inpatient outcomes among the patients with obesity. RESULTS: From 2004 to 2014, estimated 1,212,475 ACDFs were identified in which 9.2% of the patients were obese. The incidence of obesity amongst ACDF patients has risen dramatically during those years from 5.8% to 13.4%. Obese ACDF patients had higher inpatient likelihood of dysphagia, neurological, respiratory, and hematologic complications as well as pulmonary emboli, and intraoperative durotomy. CONCLUSION: Obesity is a well-established modifiable comorbidity that leads to increased perioperative complications in various surgical specialties. We present one of the largest retrospective analyses evaluating the effects of obesity on inpatient complications following ACDF. Our data suggest that the number of obese patients undergoing ACDF is steadily increasing and had a higher inpatient likelihood of developing perioperative complications.

Peroneal Tendinosis and Subluxation.

Peroneal tendinosis and subluxation are lifestyle-limiting conditions that can worsen if not properly diagnosed and treated. Adequate knowledge of ankle anatomy and detailed history and comprehensive physical examination is essential for diagnosis. Peroneal tendinopathy is likely to result from overuse, whereas subluxation often precipitates from forceful contraction of peroneals during sudden dorsiflexion while landing or abruptly stopping. In athletes, conservative measures remain first-line treatment of tendinopathy, but surgery is often immediately indicated in cases of recurrent symptomatic subluxation or dislocation. Surgical technique varies on the type, mechanism, and severity of injury, but most procedures have a high success rate.

Effects of menopausal state on lumbar decompression and fusion surgery.

Menopause leads to fluctuations in androgenic hormones which directly affect bone metabolism. Bone resorption, mineralization, and remodeling at fusion sites are essential in order to obtain a solid and biomechanically stable fusion mass. Bone metabolic imbalance seen in the postmenopausal state may predispose to fusion related complications. The aim of this study was to investigate fusion outcomes in lumbar spinal fusion surgery in women based on menopausal status. A retrospective analysis of all female patients who underwent posterior lumbar decompression and fusion at a single institution from 2013 to 2017 was performed. A total of 112 patients were identified and stratified into premenopausal (n = 25) and postmenopausal (n = 87) groups. Clinical and radiographic data was assessed at 1 year follow up. Postmenopausal patients had a higher rates of pseudarthrosis (11.63% vs 0%, p = 0.08), PJK (15.1% vs 4%, p = 0.14), and revision surgery (3.5% vs 0%, p = 0.35). The number of levels fused was associated with increased risk of pseudarthrosis (OR 1.4, p = 0.02); however, there was no association between age, hormonal use, prior tobacco use, or T-score. Age was associated with increased risk of developing PJK (OR = 1.11, p = 0.01); however, PJK was not associated with menopause, hormonal use, prior tobacco use, or T-score. Revision surgery was not associated with age, hormonal use, prior tobacco use, or T-score. This study suggests that postmenopausal women may be prone to have higher rates of pseudarthrosis, PJK and revision surgery, although our results were not statistically significant. Larger studies with longer follow up will help elucidate the true effects of menopause in spine surgery.

Soft Tissue Masses in Patients Who Underwent Cosmetic Fat Transfer Procedures for Gluteal Augmentation: A Report of 3 Cases.

CASES: Three patients were referred to our musculoskeletal oncology service after undergoing autologous fat grafting procedures. Two masses were suspected to be "soft tissue sarcomas," and one was due to a mass of unknown origin. These findings have not been reported in the orthopedic literature and may generate potential referrals for orthopedic oncologists. CONCLUSIONS: Awareness of potential complications of procedures from other surgical specialties and their radiographic characteristics is of utmost importance. The clinical and radiographic findings that could assist in distinguishing a mass related to an autologous fat transfer procedure from a soft tissue sarcoma are described.

Short-term safety of tranexamic acid use in posterior cervical decompression and fusion surgery.

Posterior cervical decompression and fusion (PCDF) can result in substantial blood loss, leading to blood transfusions and associated complications, such as infections, hypotension and organ damage. The antifibrinolytic tranexamic acid (TXA), an inhibitor of the activation of plasminogen, has been shown to be beneficial in multiple surgical procedures without any apparent increase in postoperative complications. However, there are only few studies reporting TXA utilization in cervical spine surgery and there is currently no literature detailing the short-term safety of its use in this setting. The purpose of our study is to determine the safety profile of TXA in posterior cervical decompression and fusion. From January 2015 to April 2018, 47 patients were identified to have undergone PCDF, 19 with the utilization of a TXA protocol at our institution. The incidence of adverse events was evaluated in the perioperative period and at 1 month follow-up. Of 39 patients, Nineteen (49%) received TXA as per our instructional protocol and 20 (51%) did not. Post-operative blood was significantly reduced (453 ml vs 701 ml; p = 0.03) in the group that received TXA. There was also a significant reduction in duration of surgery associated with TXA use (269 min vs 328 min; p = 0.05). There were no complications on the first 30 days after surgical intervention on the TXA group. TXA use during PCDF is a safe, effective method to reduce postoperative blood loss. Considering the limited number of patients in this study, these results should be validated on a larger group of patients.

Fish-Mouth Thoracic Fracture Fixation with Minimally Invasive Percutaneous Reduction: A Technical Note.

BACKGROUND: Surgical stabilization of thoracic spine fractures is recommended for unstable patterns, yet much debate exists regarding the best approach for reduction. The aim of this article was to report the outcome of a novel method for stabilization of a fish-mouth thoracic spine fracture. METHODS: A retrospective patient chart review was conducted. Data collected included blood loss, operative time, length of stay, perioperative complications, neurologic deficits, and secondary procedures. The patient underwent percutaneous reduction of a hyperextension injury to the thoracic spine. Sufficient reduction was achieved through a percutaneous approach, followed by sequential distraction of 1 rod with sequential locking of the contralateral rod to maintain deformity correction. Electrophysiologic monitoring was used during the procedure. RESULTS: Sufficient fracture reduction was achieved and evaluated on postoperative computed tomography. Operative time was 145 minutes, and estimated blood loss was 120 mL. There were no cerebrospinal fluid leaks, iatrogenic neurologic deficits, implant failures, other systemic events or revisions during the 8-month follow-up. CONCLUSIONS: This article describes the feasibility of using a novel model for reduction and stabilization of fish-mouth thoracic spine fracture with minimal soft tissue violation.

Histone acetyltransferase-deficient p300 mutants in diffuse large B cell lymphoma have altered transcriptional regulatory activities and are required for optimal cell growth.

BACKGROUND: Recent genome-wide studies have shown that approximately 30% of diffuse large B-cell lymphoma (DLBCL) cases harbor mutations in the histone acetyltransferase (HAT) coactivators p300 or CBP. The majority of these mutations reduce or eliminate the catalytic HAT activity. We previously demonstrated that the human DLBCL cell line RC-K8 expresses a C-terminally truncated, HAT-defective p300 protein (p300ΔC-1087), whose expression is essential for cell proliferation. METHODS: Using results from large-scale DLBCL studies, we have identified and characterized a second C-terminally truncated, HAT-defective p300 mutant, p300ΔC-820, expressed in the SUDHL2 DLBCL cell line. Properties of p300ΔC-820 were characterized in the SUDHL2 DLBCL cell line by Western blotting, co-immunoprecipitation, and shRNA gene knockdown, as well by using cDNA expression vectors for p300ΔC-820 in pull-down assays, transcriptional reporter assays, and immunofluorescence experiments. A mass spectrometry-based method was used to compare the histone acetylation profile of DLBCL cell lines expressing various levels of wild-type p300. RESULTS: We show that the SUDHL2 cell line expresses a C-terminally truncated, HAT-defective form of p300 (p300ΔC-820), but no wild-type p300. The p300ΔC-820 protein has a wild-type ability to localize to subnuclear "speckles," but has a reduced ability to enhance transactivation by transcription factor REL. Knockdown of p300ΔC-820 in SUDHL2 cells reduced their proliferation and soft agar colony-forming ability. In RC-K8 cells, knockdown of p300ΔC-1087 resulted in increased expression of mRNA and protein for REL target genes A20 and IκBα, two genes that have been shown to limit the growth of RC-K8 cells when overexpressed. Among a panel of B-lymphoma cell lines, low-level expression of full-length p300 protein, which is characteristic of the SUDHL2 and RC-K8 cells, was associated with decreased acetylation of histone H3 at lysines 14 and 18. CONCLUSIONS: The high prevalence of p300 mutations in DLBCL suggests that HAT-deficient p300 activity defines a subtype of DLBCL, which we have investigated using human DLBCL cell lines RC-K8 and SUDHL2. Our results suggest that truncated p300 proteins contribute to DLBCL cell growth by affecting the expression of specific genes, perhaps through a mechanism that involves alterations in global histone acetylation.