Combining single molecule atomic force microscopy (AFM) and protein engineering techniques, here we demonstrate that we can use recombination-based techniques to engineer novel elastomeric proteins by recombining protein fragments from structurally homologous parent proteins. Using I27 and I32 domains from the muscle protein titin as parent template proteins, we systematically shuffled the secondary structural elements of the two parent proteins and engineered 13 hybrid daughter proteins. Although I27 and I32 are highly homologous, and homology modeling predicted that the hybrid daughter proteins fold into structures that are similar to that of parent protein, we found that only eight of the 13 daughter proteins showed b-sheet dominated structures that are similar to parent proteins, and the other five recombined proteins showed signatures of the formation of significant a-helical or random coil-like structure. Single molecule AFM revealed that six recombined daughter proteins are mechanically stable and exhibit mechanical properties that are different from the parent proteins. In contrast, another four of the hybrid proteins were found to be mechanically labile and unfold at forces that are lower than the ;20 pN, as we could not detect any unfolding force peaks. The last three hybrid proteins showed interesting duality in their mechanical unfolding behaviors. These results demonstrate the great potential of using recombination-based approaches to engineer novel elastomeric protein domains of diverse mechanical properties. Moreover, our results also revealed the challenges and complexity of developing a recombination-based approach into a laboratory-based directed evolution approach to engineer novel elastomeric proteins.Keywords: single-molecule force spectroscopy; elastomeric protein; recombination; mechanical stability; mechanical unfolding Elastomeric proteins are an important class of mechanical proteins that are subject to stretching force under physiological conditions (Labeit and
361 Background: Surgical resection offers the only hope for long-term disease control in patients (pts) with pancreatic adenocarcinoma. Randomized trials (ESPAC 1, ESPAC3) further support a role for adjuvant chemotherapy (AC) in the management of pancreatic cancer (PC). Trial outcomes may not reflect clinical reality due to pt selection bias, and it is often difficult to predict which pts are most likely to benefit from adjuvant intervention. Methods: Consecutive pts between 2003 and 2008 referred to the BC Cancer Agency (BCCA) with operative intent at diagnosis (dx) were retrospectively reviewed. Results: 145 pts were identified; median age 65 years (y) (range 38-84), male/female (45.5%, 54.5%). EUS/PET staging was performed in 21% of pts. Median CA19-9 value at dx was 210 ku/L. Pancreaticoduodenectomy was performed in 65% of pts. Complete resection (RO) of tumours occurred in 87 pts (60%) overall. 66% of pts were node positive. 43% of pts were subsequently treated with adjuvant therapy (AT) where 5% of these pts received chemoradiotherapy and 95% received AC (65% gemcitabine). There was no statistically significant difference in either OS (p=0.39) or DFS (p=0.28) amongst resected pts who were treated by sx alone versus pts who received AC. In subgroup analysis, AC was associated with significantly improved OS in pts (n=58) with positive margins (R1) (median 17.3 mos vs 8.9 mos, p=0.0045) but benefit was not seen in R0 pts (n=87) (22.9 mos vs 22.4 mos, p=0.20). In multivariate analysis, poor performance status (ECOG 3-4), weight loss of more than 10% of initial body weight, baseline CA19-9 value greater than 210 ku/L, positive nodes, R1 status and histological grade 3-4 were significant adverse prognostic factors. Conclusions: PC continues to have poor outcomes with a 5yOS of 5% in pts treated with sx alone. Among pts with resectable PC treated at the BCCA, AC tended towards increased DFS and OS. Although R1 status was associated with inferior OS, the benefit of AT was greater in this subgroup. [Table: see text]
Lung cancer is the leading cause of cancer death in developed countries both for men and women; and the second most common type of cancer diagnosed, with less than 15% of patients surviving beyond 5 years. Since more than 60% of lung adenocarcinomas and more than 90% of lung squamous cell carcinomas express high levels of EGFR mRNA and protein, it has been the focus of efforts to develop new agents that target the EGFR pathway. Clinical trials have demonstrated that patient selection plays a major role for patient response. Patients that present amplification or activating mutations (L878R or exon 19 deletions) of EGFR, have higher response rates. Selection improved response rates from less than 10% to over 60–80%. Despite the promising results, all patients that receive TKI therapy develop resistance to treatment in less than one year. The mechanisms of resistance to EGFR TKi's described so far are those dependant on the overactivation/amplification of other receptor tyrosine kinases (RTK) capable to sustain anti-apoptotic signaling pathways. Our study proposes the use of genome-wide screenings using an 80,000 shRNA library on EGFR resistant cells can identify new genes that mediate the resistance to EGFR targeted therapy and provide the basis for designing new therapeutic approaches to avoid the emergence of resistance. So far, we have generated a shortlist of gene candidates that confer synergistic synthetic lethal interactions with EGFR targeted therapies and that are also highly expressed in resistant cells. We are currently overexpressing candidate genes in sensitive cells searching for those that can confer resistance to EGFR targeted therapies. Our study proposes target genes that can synergize with the current treatments to create new therapeutical strategies that can avoid the acquisition of resistance to targeted therapies. Overall, the information gained from this type of study can be applicable to tumors where ERBB receptor(s) play an important role and targeted therapies are currently used.
Lung cancer is the leading cause of cancer death in developed countries both for men and women; and the second most common type of cancer diagnosed, with less than 15% of patients surviving beyond 5 years. Since more than 60% of lung adenocarcinomas and more than 90% of lung squamous cell carcinomas express high levels of EGFR mRNA and protein, it has been the focus of efforts to develop new agents that target the EGFR pathway. Clinical trials have demonstrated that patient selection plays a major role for patient response. Patients that present amplification or activating mutations (L878R or exon 19 deletions) of EGFR, have higher response rates. Selection improved response rates from less than 10% to over 60-80%. Despite the promising results, all patients that receive TKI therapy develop resistance to treatment in less than one year. The mechanisms of resistance to EGFR TKi's described so far are those dependant on the overactivation/amplification of other receptor tyrosine kinases (RTK) capable to sustain anti-apoptotic signaling pathways. Our study proposes the use of genome-wide screenings using an 80,000 shRNA library on EGFR resistant cells can identify new genes that mediate the resistance to EGFR targeted therapy and provide the basis for designing new therapeutic approaches to avoid the emergence of resistance. So far, we have generated a shortlist of gene candidates that confer synergistic synthetic lethal interactions with EGFR targeted therapies and that are also highly expressed in resistant cells. We are currently overexpressing candidate genes in sensitive cells searching for those that can confer resistance to EGFR targeted therapies. Our study proposes target genes that can synergize with the current treatments to create new therapeutical strategies that can avoid the acquisition of resistance to targeted therapies. Overall, the information gained from this type of study can be applicable to tumors where ERBB receptor(s) play an important role and targeted therapies are currently used. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1232. doi:1538-7445.AM2012-1232
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