Prospective Outpatient Follow-Up of Early Cognitive Impairment in Patients with Mild Traumatic Brain Injury and Intracranial Hemorrhage

INTRODUCTION

Mild traumatic brain injury (mTBI) encompasses a spectrum of disability including early cognitive impairment (ECI). The Brain Injury Guidelines (BIG) suggest mTBI patients can be safely discharged from the Emergency Department. Although half of mTBI patients with intracranial hemorrhage (ICH) have evidence of ECI, it is unclear what percentage of these patients' ECI persists after discharge. We hypothesize a significant proportion of trauma patients with mTBI and ECI at presentation have persistent ECI at 30-day follow-up.

METHODS

A single-center prospective cohort study including adult trauma patients with ICH or skull fracture plus a Glasgow coma scale (GCS) of 13-15 on arrival was performed. Participants were screened for ECI using the Rancho Los Amigos Scale (RLA), and ECI was defined as a RLA < 8. We compared ECI and non-ECI groups for demographics, injury profile, computed tomography (CT) imaging (e.g., Rotterdam CT score) and outcomes with bivariate analysis. 30-day follow up phone calls were performed to re-evaluate RLA for persistent ECI and concussion symptoms.

RESULTS

From 62 patients with ICH or skull fracture and mTBI, 21 (33.9%) had ECI. Patients with ECI had a higher incidence of subarachnoid hemorrhage (85.7% versus 46.3%, p=0.003) and higher Rotterdam CT score (p=0.004) compared to those without ECI. On 30-day follow up, 6 of 21 patients (26.6%) had persistent ECI. In addition, 7 (33.3%) patients had continued concussion symptoms.

CONCLUSION

Over one-third of mTBI patients with ICH had ECI. At 30-day post-discharge follow-up over one-fourth of these patients had persistent ECI and 33% had concussion symptoms. This highlights the importance of identifying ECI prior to discharge as a significant portion may have ongoing difficulties reintegrating into work and society.

Intraoperative Anastomotic Evaluation Methods: Rigid Proctoscopy Versus Flexible Endoscopy

INTRODUCTION

Rigid proctosigmoidoscopy (RP) and flexible sigmoidoscopy (FS) are two modalities commonly used for intraoperative evaluation of colorectal anastomoses. This study seeks to determine whether there is an association between the endoscopic modality used to evaluate colorectal anastomoses and the rate of anastomotic leak (AL), organ space infection, and overall infectious complication.

METHODS

The 2012-2018 American College of Surgeons National Surgical Quality Improvement Program database was queried for patients undergoing colorectal anastomoses. Anastomotic evaluation method (RP versus FS) was identified by Current Procedural Terminologycoding and used for group classification. Outcomes measured included AL, organ space infections, and overall infection. Multivariable logistic regression analysis for predicting AL was performed.

RESULTS

We identified 7100 patients who underwent a colorectal anastomosis with intraoperative endoscopic evaluation. RP was utilized in 3397 (47.8%) and FS in 3703 (52.2%) patients. RP was used more commonly in diverticulitis (44.5% versus 36.2%, P < 0.01), while FS was used more frequently in malignancy (47.5% versus 36.7%, P < 0.01). Anastomotic evaluation with FS was associated with lower rates of organ space infection (3.8% versus 4.8%, P = 0.025) and AL (2.9% versus 3.8%, P = 0.028) compared to RP. On multivariate logistic regression modeling, anastomotic evaluation with RP was associated with a higher risk of AL (odds ratio 1.403, 95% CI 1.028-1.916, P = 0.033) compared to FS.

CONCLUSIONS

Compared to FS, rigid proctosigmoidoscopic evaluation of a colorectal anastomosis was associated with an increased rate of AL and organ space infection.

Discrepancies in Thyroidectomy Outcomes Between General Surgeons and Otolaryngologists

Thyroidectomy is a common operation, performed by general surgeons and otolaryngologists. Few studies compare complication rates between these two specialties. We hypothesized that there would be no difference in the incidence of postoperative complications including recurrent laryngeal nerve (RLN) injury, hypocalcemia, or hematoma based on the surgical specialty performing the thyroidectomy. The 2016-2017 National Surgical Quality Improvement Program Targeted Thyroidectomy database was queried for patients who underwent thyroidectomy for both benign and malignant thyroid diseases. Thyroidectomies performed by general surgeons were compared to those performed by otolaryngologists. Multivariate logistic regression was used to identify risk factors associated with RLN injury, hematoma, and hypocalcemia. From 11,595 patients, 6313 (54.4%) were performed by general surgeons and 5282 (45.6%) by otolaryngologists. Goiter (43.7%) and nodule/neoplasm (40.8%) were the most common indications for the general surgery and otolaryngology cohorts respectively. General surgeons used an energy vessel sealant device more frequently (77.7% vs. 51.5%, p < 0.001), whereas RLN monitoring (67.4% vs. 58.3%, p < 0.001) and drain placement (44.3% vs. 14.8%, p < 0.001) were utilized more often by otolaryngology. After controlling for covariates, thyroidectomy by general surgeons had an increased associated risk of RLN injury (OR = 1.26, CI = 1.07-1.48, p = 0.006) and post-operative hypocalcemia (OR = 1.17, CI = 1.00-1.37, p = 0.046). Thyroidectomy volume is relatively equally distributed among general surgeons and otolaryngologists. Operation by a general surgeon is associated with an increased risk for RLN injury and postoperative hypocalcemia. This discrepancy may be explained by case volume, training, and/or completion of an endocrine surgery fellowship; however, this discrepancy still merits ongoing attention.

Predicting Unplanned Intensive Care Unit Admission for Trauma Patients: The CRASH Score

INTRODUCTION

Unplanned transfer of trauma patients to the intensive care unit (ICU) carries an associated increase in mortality, hospital length of stay, and cost. Trauma teams need to determine which patients necessitate ICU admission on presentation rather than waiting to intervene on deteriorating patients. This study sought to develop a novel Clinical Risk of Acute ICU Status during Hospitalization (CRASH) score to predict the risk of unplanned ICU admission.

METHODS

The 2017 Trauma Quality Improvement Program database was queried for patients admitted to nonICU locations. The group was randomly divided into two equal sets (derivation and validation). Multiple logistic regression models were created to determine the risk of unplanned ICU admission using patient demographics, comorbidities, and injuries. The weighted average and relative impact of each independent predictor were used to derive a CRASH score. The score was validated using area under the curve.

RESULTS

A total of 624,786 trauma patients were admitted to nonICU locations. From 312,393 patients in the derivation-set, 3769 (1.2%) had an unplanned ICU admission. A total of 24 independent predictors of unplanned ICU admission were identified and the CRASH score was derived with scores ranging from 0 to 32. The unplanned ICU admission rate increased steadily from 0.1% to 3.9% then 12.9% at scores of 0, 6, and 14, respectively. The area under the curve for was 0.78.

CONCLUSIONS

The CRASH score is a novel and validated tool to predict unplanned ICU admission for trauma patients. This tool may help providers admit patients to the appropriate level of care or identify patients at-risk for decompensation.

Applicant Perspectives of Virtual General Surgery Residency Interviews

BACKGROUND

The coronavirus 2019 (COVID-19) pandemic prompted drastic changes to residency recruitment. The majority of general surgery residency interviews for the 2020-2021 interview cycle were restructured into a virtual format. The goal of this study is to evaluate general surgery residency applicants' perception of virtual interviews.

METHODS

A secure, anonymous, web-based survey was developed, tested, and distributed via email to all candidates who applied to the University of California Irvine general surgery residency program for Match 2021.

RESULTS

1239 general surgery applicants were invited after Match Day 2021 to take the survey, and 167 (13.5%) completed the survey and were included in the final analysis. Applicants received and accepted a median of 10 (Interquartile range [IQR], 5-18) and 9 (IQR, 5-15) interviews. Using a Likert scale, candidates revealed they were most satisfied with introduction and program overview (72.5%) and interactions with faculty (70.6%). Applicants were dissatisfied with pre-interview socials (66.9%) and hospital tours (66.2%). When evaluating programs, they had the most difficulty discerning program culture and resident autonomy. Most applicants (54%) were satisfied with the virtual format and 52% believed that virtual format should continue.

DISCUSSION

The majority of applicants were satisfied with virtual interviews and could foresee the format continuing in the future.

Dawn of a New Normal: Resident and Faculty Attitudes in Adopting Virtual Conferences and Education

Background

The COVID-19 pandemic has dramatically changed education in medical residencies with the need to transition to a virtual format. The objective of this study is to assess the adoption of a virtual format for grand rounds, M&M, and education of the surgical department.

Method

A 25 question online survey was developed using Qualtrics and distributed to faculty and resident physicians in the Department of Surgery from March to April 2021.

Results

Fifty four out of 79 potential respondents (68%) completed the survey. Twenty-seven out of 54 (50%) respondents stated they were more likely to be participating in another activity most of the time or always. During to in-person conferences, 20/54 (37%) of participants reported being more distracted by other activities. Forty-two out of 54 (78%) participants strongly agree that virtual conferences are more flexible with their schedule and saves them travel time. All of the faculty want conferences to continue virtually (with or without an in-person component) citing virtual conferences are more flexible with their schedule and saves travel time. However, 4/26 (15%) of residents responded not wanting to continue virtual education citing work distractions and not truly having protected time.

Conclusion

As the Coronavirus 2019 (COVID-19) pandemic is continuing with new variants, the virtual education and conference format is necessary. There is overwhelming support from both residents and faculty in favor of the virtual conference format due to flexibility, ease, and convenience. However, care must be taken to make sure that resident education time is truly protected.

Moderate to severe leukocytosis with vasopressor use is associated with increased mortality in trauma patients

Background

Leukocytosis is a rise in white blood cell (WBC) count and clinical outcomes of moderate to severe leukocytosis in trauma patients have not been described. We hypothesized that trauma patients with severe leukocytosis (SL; ≥40.0 × 109 leukocytes/L) have higher rates of in-hospital complications and mortality than those with moderate leukocytosis (ML; 25.0-39 × 109 leukocytes/L).

Methods

We performed a retrospective analysis (2010-2017) on trauma patients developing ML or SL at a single Level-I trauma center. A multivariable logistic regression analysis for risk factors were performed.

Results

From 15,807 trauma admissions, 332 (2.1%) had ML or SL. Of these, 308 (92.8%) were ML and 24 (7.2%) were SL. Patients with ML and SL reached their peak WBC count in 1 and 10 days after admission respectively (p < 0.001). SL patients suffered higher rates of in-hospital complications (p < 0.05) and mortality compared to those without ML or SL (14.5% vs. 3.3%, p < 0.001). Between ML and SL, mortality rates rose with leukocytosis severity (13.3% vs. 29.2%, p = 0.03). Among all patients with ML or SL, vasopressor use was the strongest independent risk factor for mortality (OR 12.61, p < 0.001).

Conclusion

Clinicians should be weary of the increased mortality rates and in-hospital complications in SL patients. Among patients with ML or SL, vasopressor use, rather than SL, was the strongest predictor of mortality. Patients with ML had a quicker time course to peak leukocytosis compared to SL, suggesting these two entities to be distinct in etiology and outcome, warranting future research.

Comparison of National Surgical Quality Improvement Program Surgical Risk Calculator, Trauma and Injury Severity Score, and American Society of Anesthesiologists Physical Status to predict operative trauma mortality in elderly patients

BACKGROUND

The Trauma and Injury Severity Score (TRISS) uses anatomical and physiologic variables to predict mortality. Elderly (65 years or older) trauma patients have increased mortality and morbidity for a given TRISS, in part because of functional status and comorbidities. These factors are incorporated into the American Society of Anesthesiologists Physical Status (ASA-PS) and National Surgical Quality Improvement Program Surgical Risk Calculator (NSQIP-SRC). We hypothesized scoring tools using comorbidities and functional status to be superior at predicting mortality, hospital length of stay (LOS), and complications in elderly trauma patients undergoing operation.

METHODS

Four level I trauma centers prospectively collected data on elderly trauma patients undergoing surgery within 24 hours of admission. Using logistic regression, five scoring models were compared: ASA-PS, NSQIP-SRC, TRISS, TRISS-ASA-PS, and TRISS-NSQIP-SRC.Brier scores and area under the receiver operator characteristics curve were calculated to compare mortality prediction. Adjusted R2 and root mean squared error were used to compare LOS and predictive ability for number of complications.

RESULTS

From 122 subjects, 9 (7.4%) died, and the average LOS was 12.9 days (range, 1-110 days). National Surgical Quality Improvement Program Surgical Risk Calculator was superior to ASA-PS and TRISS at predicting mortality (area under the receiver operator characteristics curve, 0.978 vs. 0.768 vs. 0.903; p = 0.007). Furthermore, NSQIP-SRC was more accurate predicting LOS (R2, 25.9% vs. 13.3% vs. 20.5%) and complications (R2, 34.0% vs. 22.6% vs. 29.4%) compared with TRISS and ASA-PS. Adding TRISS to NSQIP-SRC improved predictive ability compared with NSQIP-SRC alone for complications (R2, 35.5% vs. 34.0%; p = 0.046). However, adding ASA-PS or TRISS to NSQIP-SRC did not improve the predictive ability for mortality or LOS.

CONCLUSION

The NSQIP-SRC, which includes comorbidities and functional status, had superior ability to predict mortality, LOS, and complications compared with TRISS alone in elderly trauma patients undergoing surgery.

LEVEL OF EVIDENCE

Prognostic and Epidemiologic; Level III.

Inborn Versus Outborn Delivery in Neonates With Congenital Diaphragmatic Hernia

BACKGROUND

Congenital diaphragmatic hernia (CDH) is a morbid and potentially fatal condition that challenges providers. The aim of this study is to compare outcomes in neonates with prenatally diagnosed CDH that are inborn (delivered in the institution where definitive care for CDH is provided) versus outborn.

METHODS

Prenatally diagnosed CDH cases were identified from the Congenital Diaphragmatic Hernia Study Group (CDHSG) database between 2007 and 2019. Using risk adjustment based on disease severity, we compared inborn versus outborn status using baseline risk and multivariable logistic regression models. The primary endpoint was mortality and the secondary endpoint was need for extracorporeal life support (ECLS).

RESULTS

Of 4195 neonates with prenatally diagnosed CDH, 3087 (73.6%) were inborn and 1108 (26.4%) were outborn. There was no significant difference in birth weight, gestational age, or presence of additional congenital anomalies. There was no difference in mortality between inborn and outborn infants (32.6% versus 33.8%, P = 0.44) or ECLS requirement (30.9% versus 31.5%, P = 0.73). Among neonates requiring ECLS, outborn status was a risk factor for mortality (OR 1.51, 95% CI 1.13-2.01, P = 0.006). After adjusting for post-surgical defect size, which is not known prenatally, outborn status was no longer a risk factor for mortality for infants requiring ECLS.

CONCLUSIONS

Risk of mortality and need for ECLS for inborn CDH patients is not different to outborn infants. Future studies should be directed to establishing whether highest risk infants are at risk for worse outcomes based on center of birth.

Improved outcomes over time for adult COVID-19 patients with acute respiratory distress syndrome or acute respiratory failure

Background

COVID-19’s pulmonary manifestations are broad, ranging from pneumonia with no supplemental oxygen requirements to acute respiratory distress syndrome (ARDS) with acute respiratory failure (ARF). In response, new oxygenation strategies and therapeutics have been developed, but their large-scale effects on outcomes in severe COVID-19 patients remain unknown. Therefore, we aimed to examine the trends in mortality, mechanical ventilation, and cost over the first six months of the pandemic for adult COVID-19 patients in the US who developed ARDS or ARF.

Methods and findings

The Vizient Clinical Data Base, a national database comprised of administrative, clinical, and financial data from academic medical centers, was queried for patients ≥ 18-years-old with COVID-19 and either ARDS or ARF admitted between 3/2020-8/2020. Demographics, mechanical ventilation, length of stay, total cost, mortality, and discharge status were collected. Mann-Kendall tests were used to assess for significant monotonic trends in total cost, mechanical ventilation, and mortality over time. Chi-square tests were used to compare mortality rates between March-May and June-August.

110,223 adult patients with COVID-19 ARDS or ARF were identified. Mean length of stay was 12.1±13.3 days and mean total cost was $35,991±32,496. Mechanical ventilation rates were 34.1% and in-hospital mortality was 22.5%. Mean cost trended downward over time (p = 0.02) from $55,275 (March) to $18,211 (August). Mechanical ventilation rates trended down (p<0.01) from 53.8% (March) to 20.3% (August). Overall mortality rates also decreased (p<0.01) from 28.4% (March) to 13.7% (August). Mortality rates in mechanically ventilated patients were similar over time (p = 0.45), but mortality in patients not requiring mechanical ventilation decreased from March-May compared to June-July (13.5% vs 4.6%, p<0.01).

Conclusions

This study describes the outcomes of a large cohort with COVID-19 ARDS or ARF and the subsequent decrease in cost, mechanical ventilation, and mortality over the first 6 months of the pandemic in the US.

Prehospital Variables Alone Can Predict Mortality After Blunt Trauma: A Novel Scoring Tool

BACKGROUND

We sought to develop a novel Prehospital Injury Mortality Score (PIMS) to predict blunt trauma mortality using only prehospital variables.

STUDY DESIGN

The 2017 Trauma Quality Improvement Program database was queried and divided into two equal sized sets at random (derivation and validation sets). Multiple logistic regression models were created to determine the risk of mortality using age, sex, mechanism, and trauma activation criterion. The PIMS was derived using the weighted average of each independent predictor. The discriminative power of the scoring tool was assessed by calculating the area under the receiver operating characteristics (AUROC) curve. The PIMS ability to predict mortality was then assessed by using the validation cohort. The score was compared to the Revised Trauma Score (RTS) using the AUROC curve, including a subgroup of patients with normal vital signs.

RESULTS

The derivation and validation groups each consisted of 163 694 patients. Seven independent predictors of mortality were identified, and the PIMS was derived with scores ranging from 0 to 20. The mortality rate increased from 1.4% to 43.9% and then 100% at scores of 1, 10, and 19, respectively. The model had very good discrimination with an AUROC of .79 in both the derivation and validation groups. When compared to the RTS, the AUROC were similar (.79 vs. .78). On subgroup analysis of patients with normal prehospital vital signs, the PIMS was superior to the RTS (.73 vs. .56).

CONCLUSION

The PIMS is a novel scoring tool to predict mortality in blunt trauma patients using prehospital variables. It had improved discriminatory power in blunt trauma patients with normal vital signs compared to the RTS.

Outcomes of Complex Gastrointestinal Cancer Resection at US News & World Report Top-Ranked vs Non-Ranked Hospitals

BACKGROUND

The US News & World Report (USNWR) annual ranking of the best hospitals for gastroenterology and gastrointestinal surgery offers direction to patients and healthcare providers, especially for recommendations on complex medical and surgical gastrointestinal (GI) conditions. The objective of this study was to examine the outcomes of complex GI cancer resections performed at USNWR top-ranked, compared to non-ranked, hospitals.

STUDY DESIGN

Using the Vizient database, data for patients who underwent esophagectomy, gastrectomy, and pancreatectomy for malignancy between January and December 2018 were reviewed. Perioperative outcomes were analyzed according to USNWR rank status. Primary outcome was in-hospital mortality. Secondary outcomes include length of stay, mortality index (observed-to-expected mortality ratio), rate of serious complication, and cost. Secondary analysis was performed for outcomes of patients who developed serious complications.

RESULTS

There were 3,054 complex GI cancer resections performed at 42 top-ranked hospitals vs 3,608 resections performed at 198 non-ranked hospitals. The mean annual case volume was 73 cases at top-ranked hospitals compared to 18 cases at non-ranked hospitals. Compared with non-ranked hospitals, top-ranked hospitals had lower in-hospital mortality (0.96% vs 2.26%, respectively, p < 0.001) and lower mortality index (0.71 vs 1.53, respectively). There were no significant differences in length of stay, rate of serious complications, or direct cost between groups. In patients who developed serious morbidity, top-ranked hospitals had a lower mortality compared with non-ranked hospitals (8.2% vs 16.8%, respectively, p < 0.01).

CONCLUSIONS

Within the context of complex GI cancer resection, USNWR top-ranked hospitals performed a 4-fold higher case volume and were associated with improved outcomes. Patients with complex GI-related malignancies may benefit from seeking surgical care at high-volume regional USNWR top-ranked hospitals.

After Chemotherapy Treatment for Maternal Cancer During Pregnancy, Is Breastfeeding Possible?

OBJECTIVE

To report breastfeeding complaints of women diagnosed with cancer during pregnancy and correlate success with characteristics of their treatment.

MATERIALS AND METHODS

This is a prospective cohort study of women diagnosed with cancer during pregnancy who attempted breastfeeding. We surveyed participants about breast engorgement, milk let down, and consistent breast milk production through mailed questionnaires. Treatment details, including the type and number of chemotherapy cycles given during pregnancy and antepartum or postpartum depression, were collected. A single pathologist evaluated surgical specimens to note lactational changes while blinded to patient's treatment. The primary endpoint was successful breastfeeding without reporting any lack of or decreased breast milk production.

RESULTS

When comparing women who underwent chemotherapy during pregnancy to women who did not, there was a significant difference in reporting a lack of or a perceived decrease in breast milk supply and the need to provide supplemental feeding to their infants (63.5% and 9%, respectively, p < 0.001). In the women who received chemotherapy, there was no significant difference in maternal age, cancer type, or stage with regard to breastfeeding difficulties. Gestational age at the first cycle and the number of cycles were significant factors associated with breastfeeding difficulties (p = 0.006 and p = 0.0003, respectively). Antepartum and postpartum depression was not associated with decreased breast milk production. A lack of lactational changes and significant lobular atrophy were noted in the women given neoadjuvant chemotherapy.

CONCLUSION

Women who undergo chemotherapy during a pregnancy are more likely to report breastfeeding difficulties.

Abstract C31: Molecular profiling in patients with radioactive iodine-refractory thyroid cancers using targeted mutation analysis

Background: Thyroid cancer is the most common neoplasia of the endocrine system, accounting for 1%-3% of all cancers. Differentiated thyroid cancer (DTC) accounts for ∼93% of all thyroid cancers. While most cases of DTC are treated with surgery followed by radioactive iodine (RAI) ablation, 5-15% of DTC become RAI-refractory (RAI-R) resulting in a poorer prognosis and limited treatment options. In an attempt to use genetic information to predict prognosis in patients RAI-R DTC, we designed and implemented a mass spectrometry based genotyping assay panel encompassing the most significant oncogenes in thyroid cancer. Germline mutations associated with thyroid hormone dysgenesis were also included in the panel to examine their potential role in thyroid cancer prognosis.

Methods: Somatic and germline mutations were evaluated in tumor DNA using targeted mutation analysis by Sequenom MassARRAY iPLEX platform. A total of 321 assays interrogating 212 somatic mutations and 113 germline mutations in 44 genes were included in a thyroid-cancer mutational panel. Genotype-calling was manually done by the Sequenom Typer 4.0 software. Statistical significance in categorical data was determined by a χ2 test using SPSS 11.5.

Results: Of 80 patients with RAI-R DTC, 37 were male and 43 were female. Median age at diagnosis was 59 years (range 27-86). Somatic mutations were identified in 38 (47.5%) patients; mutated genes included BRAF, RAS, TP53, MET, PIK3CA, GNAS and TPO. The BRAF V600E mutation was the most prevalent somatic mutation (28.8%) and was significantly associated with regional lymph nodes metastasis (P=0.02). RAS mutations were found in 9.9% and TP53 in 6.2% of patients, while somatic mutations in other genes were rare (&lt;2.5%).

Germline mutations in 5 genes, including SLC5A5, SLC26A4, IGF1R, RAP1GAP and TG, were identified in tumor DNA. Only the TG polymorphism M1028V was detected at very high allele frequency of 61.9% while mutations in other 4 genes were detected at low allele frequencies (&lt;3%). As expected, homozygous for the TG mutation produced one and heterozygous produced two MassARRAY peaks. Notably the detected allele frequency for TG M1028V in the RAI-R DTC group analyzed is significantly higher (61.9% vs 50.9%, P=0.017) compared to previously published population allele frequency (Collins et al, 2004). Within the group analyzed, 42.5% of patients were homozygous for TG M1028V accounting for its high allele frequency. The TG M1028V was associated significantly with such clinicopathologic parameters, as regional lymph nodes metastasis (P&lt;0.01) and lymphatic invasion in primary tumor (P=0.018).

Conclusion: These data suggest that in addition to well characterized activating BRAF V600E mutation, the germline TG allele, M1028V, may have clinical significance in thyroid cancer. This is first time report that a specific TG allele may be prognostic for patients with RAI-R DTC.

Citation Information: Mol Cancer Ther 2013;12(11 Suppl):C31.

Citation Format: Tatyana Appelbaum, Waixing Tang, Stephen Stopenski, Marcia Brose. Molecular profiling in patients with radioactive iodine-refractory thyroid cancers using targeted mutation analysis. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr C31.

RAP1GAP inhibits cytoskeletal remodeling and motility in thyroid cancer cells

The functional significance of decreased RAP1GAP protein expression in human tumors is unclear. To identify targets of RAP1GAP downregulation in the thyroid gland, RAP1 and RAP2 protein expression in human thyroid cells and in primary thyroid tumors were analyzed. RAP1GAP and RAP2 were co-expressed in normal thyroid follicular cells. Intriguingly, RAP1 was not detected in normal thyroid cells, although it was detected in papillary thyroid carcinomas, which also expressed RAP2. Both RAP proteins were detected at the membrane in papillary thyroid tumors, suggesting that they are activated when RAP1GAP is downregulated. To explore the functional significance of RAP1GAP depletion, RAP1GAP was transiently expressed at the lowest level that is sufficient to block endogenous RAP2 activity in papillary and anaplastic thyroid carcinoma cell lines. RAP1GAP impaired the ability of cells to spread and migrate on collagen. Although RAP1GAP had no effect on protein tyrosine phosphorylation in growing cells, RAP1GAP impaired phosphorylation of focal adhesion kinase and paxillin at sites phosphorylated by SRC in cells acutely plated on collagen. SRC activity was increased in suspended cells, where it was inhibited by RAP1GAP. Inhibition of SRC kinase activity impaired cell spreading and motility. These findings identify SRC as a target of RAP1GAP depletion and suggest that the downregulation of RAP1GAP in thyroid tumors enhances SRC-dependent signals that regulate cellular architecture and motility.