Citations

Abstract Targeted BRAF inhibition in melanoma yields frequent and dramatic responses, which are unfortunately followed by almost universal development of therapeutic resistance. In contrast to MAP kinase pathway activation, (e.g., differential BRAF splicing, MEK1 mutations), direct gatekeeper mutations, seen with other targeted therapies, have not yet been reported in association with resistance to targeted BRAF inhibition. Through a combination of genomic profiling of clonal diversity and molecular modeling, we documented a new molecular mechanism of vemurafenib resistance in a melanoma patient, occurring by selection of a pre-existing clonal subpopulation harboring a novel mutation in the vemurafenib-binding site of BRAF. We assessed melanoma clonal diversity using a novel approach for studying tumor heterogeneity in solid tumors, based on separating cellular subpopulations by nuclear flow sorting coupled to next generation sequencing. This approach identified distinct, coexisting melanoma subpopulations prior to initiation of vemurafenib. While vemurafenib treatment suppressed multiple clonal populations, a distinct population was noted at the time of relapse, harboring both the common activating V600E and a novel L567V mutation in the vemurafenib-binding site. Molecular modeling predicted that L567V would interfere with drug binding leading to decreased therapeutic response. Using a lentiviral expression system we assessed the functional effects of the L567V mutation both alone, and in combination with V600E. Assessment of the kinase activity in an in vitro kinase assay using MEK as a substrate indicates that the L567V mutant retains kinase activity. However, expression in a panel of melanoma cell lines demonstrates that while both the V600E single mutant and the L567V single mutant respond to BRAF inhibition by decreasing the levels of phospho-Erk, the double mutant actually responds to treatment by increasing phospho-Erk levels. This is also reflected in the increased viability of cells expressing double mutant in presence of increasing drug levels (PLX4720), compared to either of the single mutants. Taken together, the data suggest that the BRAF L567V/V600E double mutant confers insensitivity to vemurafenib, and that patients harboring both mutations may demonstrate clinically significant resistance to vemurafenib. Further, this data illustrates the role of clonal heterogeneity in mediating key clinical events including response to therapy and development of resistance, a major challenge of targeted BRAF therapies. Citation Format: Aleksandar Sekulic, Ashani T. Weeraratna, Jefferey L. MacKeigan, Amanpreet Kaur, Michael O'Connell, Megan L. Goodall, Michael Barrett, Elizabeth Lenkiewitz, Tara Holley, Victoria Zismann, Michael Gordon, Gideon Bollag, Chao Zhang, Jeffrey M. Trent. Discovery and molecular modeling of a novel mutation in the vemurafenib binding site of BRAF associated with therapeutic resistance in a patient with metastatic melanoma. [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 LB-213. doi:10.1158/1538-7445.AM2014-LB-213

Abstract Human papillomavirus (HPV) appears to be responsible for dramatic increases in the incidence of oropharyngeal squamous cell carcinoma (OPSCC) in the United States in the last two decades, in spite of decreases in the incidence of smoking. It is generally assumed that the role of HPV in the development of OPSCC is identical to the one that it plays in cervical cancer where HPV infection followed by integration into the host genome and the subsequent increased expression of the E6 and E7 oncoproteins leads to increased genomic instability. The common fragile sites (CFSs) are highly unstable chromosomal regions that will be particularly sensitive to increased genomic instability and they are also hot-spots for viral integrations in cervical cancer. The CFS regions span many megabases and many of them also span extremely large genes, a number of which have been demonstrated to function as important tumor suppressors. We therefore examined the expression of very large genes in OPSCC. An analysis of RNAseq data generated on 11 OPSCCs and matched normal oropharyngeal tissue from the same patients revealed that some of the tumors had greatly decreased expression for many of the largest genes. The two genes with the greatest decreases in expression in the tumors as compared to matched normal were the known tumor suppressor PARK2 and the putative tumor suppressor DLG2, but three other large CFS genes: CTNNA3, LRP1B and DMD, and one large gene not yet precisely localized within a CFS region: PDE4D, also had much more decreased expression than any of the other large genes. Real-time RT-PCR was used to measure the expression of these six genes in a much larger number of OPSCC tumor-normal pairs. The expression of these six genes was concordant in most OPSCCs. An individual tumor generally had either decreased expression of these six genes, no changes in the expression of these genes or increased expression of all six genes. When the tumors were grouped with respect to which ones were HPV-positive or HPV-negative we observed that 40% of the HPV-positive OPSCCs had greatly decreased expression (more than 100-fold) for all six genes. Half of the HPV-negative tumors had decreased expression of these six genes, but the amount of decreased expression was much more modest (4-16 fold). Most exciting, however was that 7 of the 12 HPV-positive tumors, and three of the four of the HPV-negative patients that had decreased expression of these genes were from patients who had tumor recurrence. In contrast only one of 18 patients whose tumors did not have decreased expression of the large genes had tumor recurrence. The loss of expression of multiple large genes, many of which are derived from CFS regions, could thus be a powerful predictor for which patients will have tumor recurrence. These results also suggest a linkage between HPV-induced chromosomal instability and dramatic decreases in the expression of multiple CFS genes in some OPSCCs. Citation Format: David I. Smith, Ge Gao, Nicole Tombers, Jan Kasperbauer, Vivian Wang. Human papillomavirus and the inactivation of expression of multiple large common fragile site genes in oropharyngeal squamous cell carcinoma. [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 582. doi:10.1158/1538-7445.AM2014-582

Background Surgical site infections (SSIs) result in significant patient morbidity following immediate tissue expander breast reconstruction (ITEBR). This study determined a single institution's 30-day SSI rate and benchmarked it against that among national institutions participating in the American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP). Methods Women who underwent ITEBR with/without acellular dermal matrix (ADM) were identified using the ACS-NSQIP database between 2005 and 2011. Patient characteristics associated with the 30-day SSI rate were determined, and differences in rates between our institution and the national database were assessed. Results 12,163 patients underwent ITEBR, including 263 at our institution. SSIs occurred in 416 (3.4%) patients nationwide excluding our institution, with lower rates observed at our institution (1.9%). Nationwide, SSIs were significantly more common in ITEBR patients with ADM (4.5%) compared to non-ADM patients (3.2%, P=0.005), and this trend was observed at our institution (2.1% vs. 1.6%, P=1.00). A multivariable analysis of all institutions identified age ≥50 years (odds ratio [OR], 1.4; confidence interval [CI], 1.1-1.7), body mass index ≥30 kg/m2 vs. <25 kg/m2 (OR, 3.4; CI, 2.6-4.5), and operative time >4.25 hours (OR, 1.9; CI, 1.5-2.4) as risk factors for SSIs. Our institutional SSI rate was lower than the nationwide rate (OR, 0.4; CI, 0.2-1.1), although this difference was not statistically significant (P=0.07). Conclusions The 30-day SSI rate at our institution in patients who underwent ITEBR was lower than the nation. SSIs occurred more frequently in procedures involving ADM both nationally and at our institution.

WWOX is a gene that spans an extremely large chromosomal region. It is derived from within chromosomal band 16q23.2 which is a region with frequent deletions and other alterations in a variety of different cancers. This chromosomal band also contains the FRA16D common fragile site (CFS). CFSs are chromosomal regions found in all individuals which are highly unstable. WWOX has also been demonstrated to function as a tumor suppressor that is involved in the development of many cancers. Two other highly unstable CFSs, FRA3B (3p14.2) and FRA6E (6q26), also span extremely large genes, FHIT and PARK2, respectively, and these two genes are also found to be important tumor suppressors. There are a number of interesting similarities between these three large CFS genes. In spite of the fact that they are derived from some of the most unstable chromosomal regions in the genome, they are found to be highly evolutionarily conserved and the chromosomal region spanning the mouse homologs of both WWOX and FHIT are also CFSs in mice. Many of the other CFSs also span extremely large genes and many of these are very attractive tumor suppressor candidates. WWOX is therefore a member of a very interesting family of very large CFS genes.

Anterolateral thigh (ALT) free flaps can result in donor site wounds that cannot be closed directly, requiring immediate or delayed split‐thickness skin grafting. The use of skin grafts for such wounds can impose postoperative activity restrictions and additional wound morbidity. The purpose of the study was to investigate the efficacy of continuous external tissue expander (CETE) in achieving staged direct closure of these wounds. Outcomes of 20 ALT free flap cases with flap widths up to 15 cm treated with CETE were retrospectively reviewed. Closure of the thigh wounds was achieved in 19 cases with an average expansion time of 9.6 days. The use of a CETE device was effective in achieving staged direct (tertiary) closure and avoiding skin grafting, which further decreased donor site morbidity of large ALT free flap reconstructions. © 2014 Wiley Periodicals, Inc. Microsurgery 35:290–294, 2015.

AbstractBackgroundThe utility of diagnostic imaging in paraneoplastic autoimmune multiorgan syndrome (PAMS) is unknown.MethodsWe examined the role of diagnostic imaging in patients with PAMS evaluated at our tertiary referral center (at Mayo Clinic, Rochester, MN, USA) and in the English literature between January 1, 1996, and August 31, 2012.ResultsWe included 17 patients from our institution and 208 patients from the literature review. Of these 225 patients, 113 (50.2%) were not known to have a malignancy diagnosis at the time of PAMS diagnosis. Of the 123 patients from our institution and from the literature reported to undergo imaging studies, conventional computed tomography (CT) was the predominant imaging modality (n = 110; 89.4%); 18F‐fluorodeoxyglucose (18F‐FDG) positron emission tomography (PET)/CT was also used, albeit infrequently (n = 12; 9.8%). When CT was included in imaging to identify or confirm the presence of a malignancy, imaging was successful in all patients who ultimately were diagnosed with an associated malignancy. At our institution, a relatively high percentage (n = 7; 41%) of patients had 18F‐FDG PET/CT, which not only identified all tumors found on CT but also facilitated staging of lymphoma and guided biopsy procedures.ConclusionDiagnostic imaging is frequently utilized in PAMS with unknown malignancy. Both conventional CT and 18F‐FDG PET/CT are likely to detect the typical underlying neoplasms. Relative to conventional CT, 18F‐FDG PET/CT may provide additional useful information regarding prognosis for the likely underlying malignancies, although there is a paucity of reports describing the use of this modality for this purpose.

Adipose triglyceride lipase (ATGL), the rate-limiting enzyme for triacylglycerol (TG) hydrolysis, has long been known to be a phosphoprotein. However, the potential phosphorylation events that are involved in the regulation of ATGL function remain incompletely defined. Here, using a combinatorial proteomics approach, we obtained evidence that at least eight different sites of ATGL can be phosphorylated in adipocytes. Among them, Thr372 resides within the hydrophobic region known to mediate lipid droplet (LD) targeting. Although it had no impact on the TG hydrolase activity, substitution of phosphorylation-mimic Asp for Thr372 eliminated LD localization and LD-degrading capacity of ATGL expressed in HeLa cells. In contrast, mutation of Thr372 to Ala gave a protein that bound LDs and functioned the same as the wild-type protein. In nonstimulated adipocytes, the Asp mutation led to decreased LD association and basal lipolytic activity of ATGL, whereas the Ala mutation produced opposite effects. Moreover, the LD translocation of ATGL upon β-adrenergic stimulation was also compromised by the Asp mutation. In accord with these findings, the Ala mutation promoted and the Asp mutation attenuated the capacity of ATGL to mediate lipolysis in adipocytes under both basal and stimulated conditions. Collectively, these studies identified Thr372 as a novel phosphorylation site that may play a critical role in determining subcellular distribution as well as lipolytic action of ATGL.

AbstractBACKGROUNDMeasurement of IgG subclasses is a useful tool for investigation of humoral immune deficiency in the presence of total IgG within reference intervals and IgG4-related disease. Nephelometry has been the method of choice for quantification. We describe an LC-MS/MS method that can multiplex all 4 subclasses along with total IgG by use of either IgG subclass-specific peptide stable isotope–labeled internal standards or a surrogate digest standard for quantification and does not rely on antigen/antibody reactions.METHODSWe combined serum with labeled internal peptide standards and intact purified horse IgG. Samples were denatured, reduced, alkylated, and digested. We analyzed the digested serum by LC-MS/MS for IgG subclasses 1–4 and total IgG.RESULTSWe assayed 112 patient sera by LC-MS/MS and immunonephelometry. The mean of the slopes and R2 values for IgG1, IgG2, IgG3, IgG4, and IgG were 1.18 and 0.93, respectively. Interassay imprecision for the LC-MS/MS method was &lt;15% for total IgG and subclasses and was slightly improved by use of a calibrator peptide from an exogenous horse IgG. Summed total IgG correlated with the measured total IgG within 10%. Reference intervals and analytical measuring range were all similar to our previous validation data for the immunonephelometry assays.CONCLUSIONSTotal IgG and IgG subclasses 1, 2, 3, and 4 can be quantified by LC-MS/MS with performance comparable to nephelometry.