Association of General Surgery Resident Remediation and Program Director Attitudes With Resident Attrition

Importance

Previous studies of resident attrition have variably included preliminary residents and likely overestimated categorical resident attrition. Whether program director attitudes affect attrition has been unclear.

Objectives

To determine whether program director attitudes are associated with resident attrition and to measure the categorical resident attrition rate.

Design, Setting, and Participants

This multicenter study surveyed 21 US program directors in general surgery about their opinions regarding resident education and attrition. Data on total resident complement, demographic information, and annual attrition were collected from the program directors for the study period of July 1, 2010, to June 30, 2015. The general surgery programs were chosen on the basis of their geographic location, previous collaboration with some coauthors, prior work in surgical education and research, or a program director willing to participate. Only categorical surgical residents were included in the study; thus, program directors were specifically instructed to exclude any preliminary residents in their responses.

Main Outcomes and Measures

Five-year attrition rates (2010-2011 to 2014-2015 academic years) as well as first-time pass rates on the General Surgery Qualifying Examination and General Surgery Certifying Examination of the American Board of Surgery (ABS) were collected. High- and low-attrition programs were compared.

Results

The 21 programs represented different geographic locations and 12 university-based, 3 university-affiliated, and 6 independent program types. Programs had a median (interquartile range [IQR]) number of 30 (20-48) categorical residents, and few of those residents were women (median [IQR], 12 [5-17]). Overall, 85 of 966 residents (8.8%) left training during the study period: 15 (17.6%) left after postgraduate year 1, 34 (40.0%) after postgraduate year 2, and 36 (42.4%) after postgraduate year 3 or later. Forty-four residents (51.8%) left general surgery for another surgical discipline, 21 (24.7%) transferred to a different surgery program, and 18 (21.2%) exited graduate medical education altogether. Each program had an annual attrition rate ranging from 0.73% to 6.0% (median [IQR], 2.5% [1.5%-3.4%]). Low-attrition programs were more likely than high-attrition programs to use resident remediation (21.0% vs 6.8%; P < .001). Median (IQR) Qualifying Examination pass rates (93% [90%-98%] vs 92% [86%-100%]; P = .92) and Certifying Examination pass rates (83% [68%-84%] vs 81% [71%-86%]; P = .47) were similar. Program directors at high-attrition programs were more likely than their counterparts at low-attrition programs to agree with this statement: "I feel that it is my responsibility as a program director to redirect residents who should not be surgeons."

Conclusions and Relevance

The overall 5-year attrition rate of 8.8% was significantly lower than previously reported. Program directors at low-attrition programs were more likely to use resident remediation. Variations in attrition may be explained by program director attitudes, although larger studies are needed to further define program factors affecting attrition.

Factors Associated With Underestimation of Invasive Cancer in Patients With Ductal Carcinoma In Situ: Precautions for Active Surveillance

Importance

Recent recognition of the overdiagnosis and overtreatment of ductal carcinoma in situ (DCIS) detected by mammography has led to the development of clinical trials randomizing women with non-high-grade DCIS to active surveillance, defined as imaging surveillance with or without endocrine therapy, vs standard surgical care.

Objective

To determine the factors associated with underestimation of invasive cancer in patients with a clinical diagnosis of non-high-grade DCIS that would preclude active surveillance.

Design, Setting, and Participants

A retrospective cohort study was conducted using records from the National Cancer Database from January 1, 1998, to December 31, 2012, of female patients 40 to 99 years of age with a clinical diagnosis of non-high-grade DCIS who underwent definitive surgical treatment. Data analysis was conducted from November 1, 2015, to February 4, 2017.

Exposures

Patients with an upgraded diagnosis of invasive carcinoma vs those with a diagnosis of DCIS based on final surgical pathologic findings.

Main Outcomes and Measures

The proportions of cases with an upgraded diagnosis of invasive carcinoma from final surgical pathologic findings were compared by tumor, host, and system characteristics.

Results

Of 37 544 women (mean [SD] age, 59.3 [12.4] years) presenting with a clinical diagnosis of non-high-grade DCIS, 8320 (22.2%) had invasive carcinoma based on final pathologic findings. Invasive carcinomas were more likely to be smaller (>0.5 to ≤1.0 cm vs ≤0.5 cm: odds ratio [OR], 0.73; 95% CI, 0.67-0.79; >1.0 to ≤2.0 cm vs ≤0.5 cm: OR, 0.42; 95% CI, 0.39-0.46; >2.0 to ≤5.0 cm vs ≤0.5 cm: OR, 0.19; 95% CI, 0.17-0.22; and >5.0 cm vs ≤0.5 cm: OR, 0.11; 95% CI, 0.08-0.15) and lower grade (intermediate vs low: OR, 0.75; 95% CI, 0.69-0.80). Multivariate logistic regression analysis demonstrated that younger age (60-79 vs 40-49 years: OR, 0.84; 95% CI, 0.77-0.92; and ≥80 vs 40 to 49 years: OR, 0.76; 95% CI, 0.64-0.91), negative estrogen receptor status (positive vs negative: OR, 0.39; 95% CI, 0.34-0.43), treatment at an academic facility (academic vs community: OR, 2.08; 95% CI, 1.82-2.38), and higher annual income (>$63 000 vs <$38 000: OR, 1.14; 95% CI, 1.02-1.28) were significantly associated with an upgraded diagnosis of invasive carcinoma based on final pathologic findings.

Conclusions and Relevance

When selecting patients for active surveillance of DCIS, factors other than tumor biology associated with invasive carcinoma based on final pathologic findings may need to be considered. At the time of randomization to active surveillance, a significant proportion of patients with non-high-grade DCIS will harbor invasive carcinoma.

Complications of Diverting Ileostomy after Low Anterior Resection for Rectal Carcinoma

There have been few studies directly comparing the postoperative complications in patients with a diverting ileostomy to patients who were not diverted after low anterior resection (LAR) for rectal carcinoma. This study is a retrospective chart review of all rectal carcinoma patients (99) who underwent a LAR from January 2009 to December 2014 at Loma Linda University Medical Center and Veterans Affairs Loma Linda Healthcare System. A majority of patients were diverted (58% vs 42%). The diverted patients were more likely to have a low tumor location ( P < 0.01), preoperative chemoradiation ( P < 0.01), and more intraoperative blood loss ( P < 0.01). Our study shows a statistically significant higher overall complication rate among patients receiving a diverting ileostomy in the six months after LAR (61% vs 38%, P = 0.02). The difference is due to a higher rate of readmission (27% vs 14%) and acute kidney injury (14% vs 5%) in patients with a diverting ileostomy. It also shows that there is a higher rate of unplanned reoperation (11% vs 6%) due to anastomotic leak (17% vs 5%) in nondiverted patients. Further studies are needed to refine the specific indications to maximize the benefit of diverting ileostomy after LAR for rectal carcinoma.

Complications of Diverting Ileostomy after Low Anterior Resection for Rectal Carcinoma

There have been few studies directly comparing the postoperative complications in patients with a diverting ileostomy to patients who were not diverted after low anterior resection (LAR) for rectal carcinoma. This study is a retrospective chart review of all rectal carcinoma patients (99) who underwent a LAR from January 2009 to December 2014 at Loma Linda University Medical Center and Veterans Affairs Loma Linda Healthcare System. A majority of patients were diverted (58% vs 42%). The diverted patients were more likely to have a low tumor location (P < 0.01), preoperative chemoradiation (P < 0.01), and more intraoperative blood loss (P < 0.01). Our study shows a statistically significant higher overall complication rate among patients receiving a diverting ileostomy in the six months after LAR (61% vs 38%, P = 0.02). The difference is due to a higher rate of readmission (27% vs 14%) and acute kidney injury (14% vs 5%) in patients with a diverting ileostomy. It also shows that there is a higher rate of unplanned reoperation (11% vs 6%) due to anastomotic leak (17% vs 5%) in nondiverted patients. Further studies are needed to refine the specific indications to maximize the benefit of diverting ileostomy after LAR for rectal carcinoma.

Is Sentinel Lymph Node Dissection Necessary in All Patients with Ductal Carcinoma in Situ Undergoing Total Mastectomy?

When ductal carcinoma in situ (DCIS) is found on core needle biopsy, rates of upgrade to invasive cancer of 25 per cent and nodal positivity of 10 per cent have been reported. Sentinel lymph node dissection (SLND) is recommended when mastectomy is performed for DCIS. We investigated the role of SLND in DCIS patients undergoing partial and total mastectomy (TM). During the study period 2004 to 2013, 170 patients with DCIS were identified with a median age of 60 years (range 26–84 years). Of these, 58.2 per cent had partial mastectomy (PM) alone, 10.6 per cent had PM with SLND, and 31.1 per cent had TM with or without contralateral prophylactic mastectomy with SLND. Overall, SLND identified positive nodes in 4.2 per cent of patients. Upgrade to invasive carcinoma on final breast pathology was found in 8.2 per cent of patients overall, including 4.0 per cent of patients undergoing PM alone, 22.2 per cent undergoing PM with SLND, and 11.3 per cent for TM with SLND ( P = 0.8). In this study, patients diagnosed with DCIS on core needle biopsy had lower than expected rates of positive sentinel nodes and upgrade to invasive carcinoma. Surgeons and patients should revisit the necessity of SLND in DCIS patients undergoing mastectomy, which could lead to decreased health expenditure, resources, time, morbidity, and emotional impact on patients.

Is Sentinel Lymph Node Dissection Necessary in All Patients with Ductal Carcinoma In Situ Undergoing Total Mastectomy?

When ductal carcinoma in situ (DCIS) is found on core needle biopsy, rates of upgrade to invasive cancer of 25 per cent and nodal positivity of 10 per cent have been reported. Sentinel lymph node dissection (SLND) is recommended when mastectomy is performed for DCIS. We investigated the role of SLND in DCIS patients undergoing partial and total mastectomy (TM). During the study period 2004 to 2013, 170 patients with DCIS were identified with a median age of 60 years (range 26-84 years). Of these, 58.2 per cent had partial mastectomy (PM) alone, 10.6 per cent had PM with SLND, and 31.1 per cent had TM with or without contralateral prophylactic mastectomy with SLND. Overall, SLND identified positive nodes in 4.2 per cent of patients. Upgrade to invasive carcinoma on final breast pathology was found in 8.2 per cent of patients overall, including 4.0 per cent of patients undergoing PM alone, 22.2 per cent undergoing PM with SLND, and 11.3 per cent for TM with SLND (P = 0.8). In this study, patients diagnosed with DCIS on core needle biopsy had lower than expected rates of positive sentinel nodes and upgrade to invasive carcinoma. Surgeons and patients should revisit the necessity of SLND in DCIS patients undergoing mastectomy, which could lead to decreased health expenditure, resources, time, morbidity, and emotional impact on patients.

Overexpression of HPV16 E6* Alters β-Integrin and Mitochondrial Dysfunction Pathways in Cervical Cancer Cells

BACKGROUND

High-risk human papillomaviruses (HPV) cause nearly all cases of cervical cancer, as well as many types of oral and anogenital cancer. Alternative splicing increases the capacity of the HPV genome to encode the proteins necessary for successful completion of its infectious life cycle. However, the roles of these splice variants, including E6*, the smaller splice isoform of the E6 oncogene, in carcinogenesis are not clear.

MATERIALS AND METHODS

SiHa (HPV16(+)) and C33A (HPV(-)) cells were transfected with the E6* plasmid, and tandem mass tag-labeled protein levels were quantified by mass spectrometry. Proteomic analyses identified pathways affected by E6* in both HPV(+) and HPV(-) cells, and pathways were validated using in vitro methods.

RESULTS

A total of 4,300 proteins were identified and quantified in lysates of SiHa and C33A cells with and without HPV16 E6* expression. SiHa and C33A cells expressing E6* underwent changes in protein expression affecting integrin signaling and mitochondrial dysfunction pathways, respectively. Subsequent experiments were performed to validate selected E6*-mediated alterations in protein levels.

CONCLUSION

E6* modifies the expression of proteins involved in mitochondrial dysfunction and oxidative phosphorylation in C33A cells, and β-integrin signaling in SiHa cells.

Program Factors That Influence American Board of Surgery In-Training Examination Performance: A Multi-Institutional Study

OBJECTIVE

To determine the influence of program strategies, such as program directors' (PD) attitudes about the American Board of Surgery In-Training Examination (ABSITE) and approach to ABSITE preparation, on residents' ABSITE performance.

DESIGN

A 17-item questionnaire was sent to PDs at surgical residency programs. The questions were designed to elicit information regarding the educational curriculum, remediation protocols, and opinions relating to the ABSITE. Main outcome measure was categorical resident ABSITE percentile scores from the January 2014 examination. Statistical analysis was performed using the Student t-test, analysis of variance, and linear regression as appropriate.

SETTING

The study was carried out at general surgery residency programs across the country.

PARTICIPANTS

In total, 15 general surgery residency PDs participated in the study.

RESULTS

The PD response rate was 100%. All 460 resident ABSITE scores from the 15 programs were obtained. In total, 10 programs (67%) identified as university affiliated, 4 programs (27%) as independent academic, and 1 program (7%) as hybrid. The mean number of residents per program was 30.7 (range: 15-57). In total, 14 PDs (93%) indicated that an ABSITE review curriculum was in place and 13 PDs (87%) indicated they had a remediation protocol for residents with low ABSITE scores (with differing thresholds of <30th, <35th, and <40th percentile). The median overall ABSITE score for all residents was 61st percentile (interquartile range = 39.5). The mean ABSITE score for each program ranged from 39th to 75th percentile. Program factors associated with higher ABSITE scores included tracking resident reading throughout the year (median 63rd percentile with tracking vs 59th percentile without, p = 0.040) and the type of remediation (by PD: 77th percentile, by PD and faculty: 57th percentile, faculty only: 64th percentile, with Surgical Education and Self-Assessment Program (SESAP): 63rd percentile, outside review course: 43rd percentile; p < 0.001). Programs with a remediation protocol trended toward higher ABSITE scores compared with programs without remediation protocols (median 61st percentile vs 53rd percentile, p = 0.098). Factors not significantly associated with ABSITE performance included number of structured educational hours per week and frequency of ABSITE review sessions.

CONCLUSIONS

Program factors appear to significantly influence ABSITE performance. Programs where the PD was actively involved in remediation mentorship and the tracking of resident reading achieved higher ABSITE percentile scores on the January 2014 examination. Counterintuitively, residents from programs with a lower ABSITE threshold for remediation performed better on the examination.

Abstract 1828: Proteomic analysis of the effect of E6 star expression on cellular pathways in HPV positive SiHa and HPV negative C33A cervical carcinoma cells

High-risk types of the human papillomavirus (HR-HPV) are the causative agents of nearly all cases of cervical cancer, as well as a significant number of head, neck, penile, vulvar and anal cancers. Like many other viruses with small genomes, HPV (∼8 kb) utilizes numerous mechanisms to increase the capacity of its genome to encode the proteins necessary for successful completion of its infectious life cycle, including alternative splicing. Studies over the past few decades have focused intensively on the activities and roles of E6 proteins from HR-HPVs during the process of cellular transformation, clearly implicating E6 as a major transforming agent. In contrast, the role of the smaller splice isoform, E6*, in the carcinogenic process has not yet been established. In a recent study, we demonstrated that the over-expression of E6* reduces tumor growth by SiHa (HPV16 positive) and C33A (no HPV) cells in nude mice, suggesting that therapies emulating the actions of E6* may be of medical benefit. Furthermore, tumor growth inhibition by E6* was greater in tumors derived from HPV positive cells than in tumors derived from HPV negative cells. This difference implies that E6* interferes with the oncogenic activity of the full-length protein as well as by acting through HPV-independent mechanisms. The goal of this study is to determine the pathways affected by E6* that may lead to the observed reduction in tumor formation in xenograft models. To elucidate how E6* may affect the levels of cellular proteins and thereby orchestrate pathway regulation, in both E6 positive and negative environments, SiHa pFlag, SiHa pE6*, C33A pFlag, and C33A pE6* cells were created and their differential protein expression examined using mass spectrometry and Ingenuity Pathway Analysis (IPA) software. Lysates of these cells were reduced, alkylated, trypsinized, and TMT labeled, and the labeled peptides were analyzed using an LTQ-Orbitrap Velos mass spectrometer. Proteins were quantified by TMT tags and identified by comparison against the human library using Proteome Discoverer Software. 322 proteins were detected as differentially expressed using a 1.3 fold-change cut-off value. Further analysis by IPA revealed that E6* induced changes in apoptosis and death receptor signaling pathways in both HPV- and HPV positive cells, while other pathways, such as those involving mitochondrial dysfunction and TNFR1 signaling, were more profoundly affected in HPV negative cells. Our study provides several promising leads for future experiments and analyses, specifically in the context of human cancers, and carries with it the exciting possibility of replicating the anti-oncogenic activity of E6* in such a way as to provide therapeutic benefit. Future work will involve more detailed examination of our preliminary results and comparing these observations with those obtained from actual tumors derived from these cells.

Citation Format: Whitney Evans, Maria Filippova, Robert Aragon, Valeri Filippov, Mark E. Reeves, Penelope Duerksen-Hughes. Proteomic analysis of the effect of E6 star expression on cellular pathways in HPV positive SiHa and HPV negative C33A cervical carcinoma cells. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1828. doi:10.1158/1538-7445.AM2015-1828

Abstract 2146: RASSF1C modulation of Piwi-interacting RNAs (piRNAs) in lung cancer

Introduction: RASSF1C is emerging as an important oncoprotein in lung cancer cell growth. We have shown that RASSF1C promotes lung cancer cell proliferation and migration; and RASSF1C up-regulates important genes in lung cancer cell growth that include a stem cell self-renewal gene, piwi1 (hiwi). PIWI-like proteins are a subfamily of Argonaute proteins that interact with small PIWI-interacting RNA molecules (known as piRNAs that are 24-32 nucleotides long) to form complexes that regulate transcriptional and translational repression. This leads to inhibition of apoptosis, stimulation of cell division and proliferation, and down-regulation of cyclin inhibitors and tumor suppressors. Therefore, modulation of Piwil1-piRNA gene expression by RASSF1C suggests a potential role for RASSF1C in lung cancer stem cell development and progression. To further investigate our hypothesis, we carried out a global piRNA microarray screen to identify piRNAs that are modulated by RASSF1C in lung cancer cells.

Method: A piRNA microarray screen was performed using the lung cancer cell line H1299 stably over-expressing RASSF1C (and controls). Total RNA was extracted from experimental and control cells and was submitted to Arraystar (Rockville, MD) for the piRNA microarray screen and data analysis.

Results: The piRNA microarray screen identified several piRNAs that are regulated by RASSF1C and we have confirmed the expression of some of them in cell lines. The function of the piRNAs identified is yet to be determined. We have initiated studies to determine the function of some of the most up-regulated and down-regulated piRNA genes in lung cancer cells. We are also profiling the expression of these piRNAs in normal and lung tumor tissues.

Conclusion: Several piRNAs are target genes of RASSF1C. Characterization of the function of these piRNAs may enhance our understanding of the role of RASSF1C in promoting lung cancer stem cell growth and progression. Linking a Rassf1c-Piwil1/piRNAs axis to lung cancer stem cell development and progression could possibly lead to discovery of new diagnostic and therapeutic targets for lung cancer.

Citation Format: Yousef G. Amaar, Matthew Firek, Mark E. Reeves, Mark E. Reeves. RASSF1C modulation of Piwi-interacting RNAs (piRNAs) in lung cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2146. doi:10.1158/1538-7445.AM2015-2146

Abstract 2454: Ampk and hdac pathways and regulation rassf1c gene expression

Introduction: We have previously shown that RASSF1C promotes cell proliferation, migration and attenuates apoptosis in cancer cells. We have also shown that RASSF1C is significantly up-regulated in breast and lung cancer tissues compared to normal tissues. Together these demonstrate that RASSF1C, is not a tumor suppressor like RASSF1A, but instead appears to function as an oncoprotein.

Currently nothing is known about the upstream signaling cascades involved in regulating RASSF1C gene expression and thus we performed transcriptome PCR array study to identify chemicals inhibitors that modulate(s) RASSF1C expression.

Method: A transcriptome PCR array was obtained from Qiagen. It consisted of cDNA from breast cancer cell line MCF7 cells treated with 90 different chemical inhibitors that regulate various signaling pathways. The array was screened with RASSF1C gene specific primers. Data analysis was performed by importing the Ct values obtained into data analysis software.

Results: The PCR array screen identified several chemical reagents that appear to up-regulate and several that seem to down-regulate RASSF1C expression by ≥ 1.5 fold. The two most notable reagents are Dorsopmorhin (AMPK inhibitor) which up-regulates RASSF1C expression by 2.8 fold and Trichostatin A (HDAC inhibitor) which down regulates RASSF1C expression by 2 fold. We are in process of confirming the effect of these inhibitors in a panel of breast and lung cancer cells.

Conclusion: The findings are novel and suggest that inhibition of AMPK pathway induces RASSF1C expression while inhibition of HDAC pathway suppresses RASSF1C gene expression. We should note that Trichostatin A has been shown to activate AMPK, inhibits HDAC, arrests cell growth, and induces apoptosis in human cancers. Our findings provide a potential mechanism for regulating RASSF1C gene expression through the modulation of AMPK and HDAC pathways.

Citation Format: Yousef G. Amaar, Mark E. Reeves, Matthew Firek. Ampk and hdac pathways and regulation rassf1c gene expression. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2454. doi:10.1158/1538-7445.AM2014-2454

Evidence that RASSF1C stimulation of lung cancer cell proliferation depends on IGFBP-5 and PIWIL1 expression levels

RASSF1C is a major isoform of the RASSF1 gene, and is emerging as an oncogene. This is in contradistinction to the RASSF1A isoform, which is an established tumor suppressor. We have previously shown that RASSF1C promotes lung cancer cell proliferation and have identified RASSF1C target genes with growth promoting functions. Here, we further report that RASSF1C promotes lung cancer cell migration and enhances lung cancer cell tumor sphere formation. We also show that RASSF1C over-expression reduces the inhibitory effects of the anti-cancer agent, betulinic acid (BA), on lung cancer cell proliferation. In previous work, we demonstrated that RASSF1C up-regulates piwil1 gene expression, which is a stem cell self-renewal gene that is over-expressed in several human cancers, including lung cancer. Here, we report on the effects of BA on piwil1 gene expression. Cells treated with BA show decreased piwil1 expression. Also, interaction of IGFBP-5 with RASSF1C appears to prevent RASSF1C from up-regulating PIWIL1 protein levels. These findings suggest that IGFBP-5 may be a negative modulator of RASSF1C/ PIWIL1 growth-promoting activities. In addition, we found that inhibition of the ATM-AMPK pathway up-regulates RASSF1C gene expression.

Rate of re-excision after breast-conserving surgery for invasive lobular carcinoma

Invasive lobular carcinoma (ILC) accounts for approximately 5 to 20 per cent of all breast cancers and is often multicentric. Despite pre- and intraoperative assessments to achieve negative margins, ILC is reported to be associated with higher rates of positive margin. This cross-sectional study examined patients with breast cancer treated at our institution from 2000 to 2010. The objective was to investigate the rate of re-excision resulting from positive or close margin (1 mm or less) in patients who underwent breast-conserving surgery (BCS) for ILC compared with invasive ductal carcinoma (IDC) and ductal carcinoma in situ (DCIS). Of the 836 patients treated, 416 patients underwent BCS. The rate of re-excision after BCS for ILC was 35.1 versus 17.7 per cent for IDC and 20.0 per cent for DCIS (P = 0.04). Re-excisions were more often performed for positive margin in patients with ILC (11 of 37 [29.7%]) versus IDC (36 of 334 [10.8%]) and DCIS (five of 45 [11.1%];(P = 0.004). In this single-institution review, BCS for ILC had significantly higher rates of re-excision as a result of positive margins when compared with IDC and DCIS. Tumor size greater than 2 cm and lymph node involvement were identified as factors associated with positive surgical margin in ILC. The higher possibility of positive margins and the need for additional procedures should be discussed with patients undergoing BCS for ILC.

Small molecule- and amino acid-induced aggregation of gold nanoparticles

To understand which organic molecules are capable of binding to gold nanoparticles and/or inducing nanoparticle aggregation, we investigate the interaction of gold nanoparticles with small molecules and amino acids at variable pH. Dynamic Light Scattering (DLS) and ultraviolet-visible (UV-vis) spectra were measured on mixtures of colloidal gold with small molecules to track the progression of the aggregation of gold nanoparticles. We introduce the 522 to 435 nm UV-vis absorbance ratio as a sensitive method for the detection of colloidal gold aggregation, whereby we delineate the ability of thiol, amine, and carboxylic acid functional groups to bind to the surfaces of gold nanoparticles and investigate how combinations of these functional groups affect colloidal stability. We present models for mechanisms of aggregation of colloidal gold, including surface charge reduction and bridging linkers. For all molecules whose addition leads to the aggregation of gold nanoparticles, the aggregation kinetics were accelerated at acidic pH values. Colloidal gold is maintained only in the presence of anionic carboxyl groups, which are neutralized by protonation at lower pH. The overall reduced charge on the stabilizing carboxyl groups accounts for the accelerated aggregation at lower pH values.

Abstract 4288: RASSF1C, unlike RASSF1A, reduces TNF-α induced phosphorylation of MST1/2

Introduction: Recently, RASSF1A has been shown to mediate the apoptotic effects of TNF-α by interacting with the mammalian sterile 20-like kinase 1 and 2 (MST1/2) through the Salvador/Rassf/Hippo (SARAH) domain leading to MST1/2 phosphorylation activation of apoptosis through the Hippo pathway. In contrast, we have previously shown that RASSF1C promotes cell proliferation and attenuates apoptosis in cancer cells. Since both RASSF1A and RASSF1C contain the SARAH domain located in their identical C-termini, RASSF1C should be capable of interacting with SARAH domain-containing proteins, and could potentially attenuate MST1/2-mediated apoptosis through the Hippo pathway. Thus, in this study we have investigated the impact of RASSF1C on MST1/2 activation/phosphorylation in presence of TNF-α, including whether RASSF1C modulates MST1/2 pro-apoptotic effects through the Hippo pathway differently from RASSF1A.

Method: Breast and lung cancer cells over-expressing RASSF1A and RASSF1C were used in this study. Cells were cultured in the proper media and treated with TNF-α for 12-18 hr. Cells were collected and used for Western blot analysis utilizing antibodies that detect MST and p-MST antibodies.

Results: Our preliminary data suggest that RASSF1C over-expression decreases the phosphorylation levels of MST1/2 in TNF-α-treated breast and lung cancer cells compared to those cells over-expressing RASSF1A

Conclusion: Our findings suggest that over-expression of RASSF1C in breast and lung cancer cells may attenuate the MST1/2 apoptotic effects by sequestering of MST1/2 proteins and inhibiting their activation by phosphorylation. The findings also further support our hypothesis that RASSF1C attenuates apoptosis; and RASSF1C, unlike RASSF1A, may inhibit MST1/2 activation and hence may negatively modulate the Hippo pathway.

Citation Format: Yousef G. Amaar, Matthew Firek, Mark E. Reeves. RASSF1C, unlike RASSF1A, reduces TNF-α induced phosphorylation of MST1/2. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4288. doi:10.1158/1538-7445.AM2013-4288

Tip preparation for near-field ablation at mid-infrared wavelengths

A fabrication method for high-throughput, fiber-based tips for near-field scanning microscopy (NSOM) in the mid-infrared (λ ~ 3 μm) has been developed. Several fiber materials have been investigated and recipes for wet-chemical etching have been varied to produce tips that are physically robust and are capable of low-loss transmission of high-power pulses of mid-infrared light. Ultimately, wet-chemical etching techniques are used on glass fibers to produce tips capable of focusing mid-infrared light to ablate material from sub-micron-sized regions of organic films. The power throughput of the tips is significantly increased by using a novel material, previously unreported for NSOM applications: germanate fibers. The tips produced are mechanically strong and capable of transmitting high light fluence without sustaining physical damage. Here, the development of these tips and their performance are described.

Ras-Association Domain Family 1C Protein Enhances Breast Tumor Growth in Vivo

The Ras association domain family 1 (RASSF1) gene is a Ras effector that plays an important role in carcinogenesis. We have previously shown that silencing of RASSF1C decreases and over-expression of RASSF1C increases cell proliferation, migration, and attenuates apoptosis of breast cancer cells in vitro. To further confirm our working hypothesis that RASSF1C may play a role as a growth promoter, we have tested the growth of human breast cancer cells stably over-expressing RASSF1A or RASSF1C in nude mice. Our studies show that breast cancer cells over-expressing HA-RASSF1A developed significantly smaller tumors and cells over-expressing HA-RASSF1C developed significantly larger tumors compared to control cells expressing the vector back bone. We have confirmed the expression of HA-RASSF1A and HA-RASSF1C in tumor tissue using RT-PCR, western blotting and immunohistochemical analyses using HA-antibody. Together, our previous in vitro and current in vivo findings further support our hypothesis that RASSF1C, unlike RASSF1A, is not a tumor suppressor and rather it appears to function as tumor growth promoter in breast cancer cells.

RASSF1C modulates the expression of a stem cell renewal gene, PIWIL1

Background

RASSF1A and RASSF1C are two major isoforms encoded by the Ras association domain family 1 (RASSF1) gene through alternative promoter selection and mRNA splicing. RASSF1A is a well established tumor suppressor gene. Unlike RASSF1A, RASSF1C appears to have growth promoting actions in lung cancer. In this article, we report on the identification of novel RASSF1C target genes in non small cell lung cancer (NSCLC).

Methods

Over-expression and siRNA techniques were used to alter RASSF1C expression in human lung cancer cells, and Affymetrix-microarray study was conducted using NCI-H1299 cells over-expressing RASSF1C to identify RASSF1C target genes.

Results

The microarray study intriguingly shows that RASSF1C modulates the expression of a number of genes that are involved in cancer development, cell growth and proliferation, cell death, and cell cycle. We have validated the expression of some target genes using qRT-PCR. We demonstrate that RASSF1C over-expression increases, and silencing of RASSF1C decreases, the expression of PIWIL1 gene in NSCLC cells using qRT-PCR, immunostaining, and Western blot analysis. We also show that RASSF1C over-expression induces phosphorylation of ERK1/2 in lung cancer cells, and inhibition of the MEK-ERK1/2 pathway suppresses the expression of PIWIL1 gene expression, suggesting that RASSF1C may exert its activities on some target genes such as PIWIL1 through the activation of the MEK-ERK1/2 pathway. Also, PIWIL1 expression is elevated in lung cancer cell lines compared to normal lung epithelial cells.

Conclusions

Taken together, our findings provide significant data to propose a model for investigating the role of RASSF1C/PIWIL1 proteins in initiation and progression of lung cancer.