Measurement of high protein concentrations by optical rotation: a case study for monitoring of monoclonal antibody drug downstream processes

BACKGROUND

Recent advancements in cell engineering and bioreactor engineering have enabled high monoclonal antibody (mAb) concentrations in harvested solutions for the downstream process (DSP).

METHODS

As many unit operations such as capture chromatography, polish chromatography, membrane filtration, virus inactivation, virus filtration, and concentration by ultrafiltration are involved in DSP, it is crucial to monitor the process carefully in order to perform reliable and stable DSP operations. One of the most important signals (process parameter) to be monitored is the protein concentration C_P. Although various methods are available, most of them are not suited for measuring high C_P. In this paper, we have developed a method for measuring very high C_P by optical rotation (OR).

RESULT

Linear correlations were confirmed between OR and C_P in the range C_P = 0 to 80 g/L for mAbs with high repeatability and small variation coefficients. This method was applied to the monitoring of C_P in the opaque (colored) solution during the cell culture. The C_P by OR was in good agreement with those by the standard Protein A HPLC method.

CONCLUSION

Monitoring of high C_P by OR is expected to be an efficient process analytical tool (PAT) for DSP.

A regressive approach to the design of continuous capture process with multi-column chromatography for monoclonal antibodies

Although empirical methods have been introduced in the process development of continuous chromatography, the common approach to optimize a multi-column continuous capture chromatography (periodic counter-current chromatography, PCCC) process heavily relies on numerical model simulations and the number of experiments. In addition, different multi-column settings in PCCC add more design variables in process development. In this study, we have developed a rational method for designing PCCC processes based on iterative calculations by mechanistic model-based simulations. Breakthrough curves of a monoclonal antibody were measured at different residence times for three protein A resins of different particle sizes and capacities to obtain the parameters needed for the simulation. Numerical calculations were performed for the protein sample concentration in the range of 1.5 to 4 g/L. Regression curves were developed to describe the relative process performances compared with batch operation, including the resin capacity utilization and the buffer consumption. Another linear correlation was established between breakthrough cut-off (BT%) and a modified group composed of residence time, mass transfer coefficient, and particle size. By normalizing BT% with binding capacity and switching time, the linear regression curves were established for the three protein A resins, which are useful for the design and optimization of PCCC to reduce the process development time.

Rapid Purification of Immunoglobulin G Using a Protein A-​immobilized Monolithic Spin Column with Hydrophilic Polymers

A rapid purification method was developed for antibody production in Chinese hamster ovary (CHO) cells using a Protein A-immobilized monolithic silica spin column with hydrophilic polymers. Monolithic silica modified with copolymers of 2-hydroxyethylmethacrylate (HEMA) and glycidyl methacrylate (GMA) showed lower non-specific protein absorption than that modified with a silane reagent. The epoxy group of GMA was converted to an amino group, and Protein A was modified by the coupling reagent. The amount of immobilized Protein A was controlled by changing the ratio of GMA to HEMA and the mesopore size of monolith. A modified monolith disk was fixed to a spin column for rapid antibody purification. The linear curves (for the antibody concentrations over 10 - 300 μg/mL) had a correlation coefficient of >0.999. Our column had various analytical advantages over previously reported columns, including a shorter preparation time (<10 min) and smaller sample volumes for purification with Protein A-immobilized agarose.

Correlation between protein desorption behavior and its adsorption enthalpy change in polymer grafted anion exchange chromatography

Thermodynamic studies on protein adsorption onto chromatographic surfaces mainly focus on the molecular level interaction between proteins and ligands. Yet, not much attention is given to the study of polymer grafted ligand architecture effect on thermodynamic parameters, nor to the relation between chromatographic parameters and the directly obtained thermodynamic parameters. These relations are needed in order to confer meaning and to ease future data interpretation of thermodynamic studies of protein adsorption. In this study, the adsorption of bovine serum albumin monomer (BSA_m) onto chromatographic surfaces with grafted ligands was studied from a thermodynamic point of view together with chromatographic data. Isothermal titration calorimetry (ITC) results showed that BSA_m adsorption is exothermic (ΔH¯^ads < 0) when adsorbs onto Toyopearl GigaCapQ 650 M, Toyopearl Q600AR, and Q Sepharose XL, but endothermic (ΔH¯^ads > 0) when adsorbs onto Toyopearl SuperQ and a conventional resin (Q Sepharose Fast Flow), showing clear differences in the driving forces of adsorption caused by different ligand architectures. In addition, we found a new relation between the salt required for protein elution and the change in adsorption enthalpy (ΔH¯^ads) directly measured with ITC, intrinsically connecting both adsorption and desorption mechanisms.

Linear flow-velocity gradient chromatography-An efficient method for increasing the process efficiency of batch and continuous capture chromatography of proteins

A new method was proposed for increasing the capture chromatography process efficiency, linear flow-velocity gradient (LFG). The method uses a linear decreasing flow-velocity gradient with time during the sample loading. The initial flow velocity, the final flow velocity and the gradient time are the parameters to be tuned. We have developed a method for determining these parameters by using the total column capacity and the total loaded amount as a function of time. The capacity can be calculated by using the relationships between dynamic binding capacity (DBC) and residence time. By leveraging the capacity, loading amount, and the required conditions, the optimum LFG can be designed. The method was verified by ion-exchange and protein A chromatography of monoclonal antibodies (mAbs). A two-fold increase in the productivity during the sample loading was possible by LFG compared with the constant flow-velocity (CF) operation. LFG was also applied to a 4-column continuous process. The simulation showed that the cost of resin per unit amount of processed mAbs can be reduced by 13% while 1.4 times enhancement in productivity was preserved after optimization by LFG compared to CF. The process efficiency improvement is more pronounced when the isotherm is highly favorable and the loading volume is large.

Microcalorimetric Analysis of the Adsorption of Lysozyme and Cytochrome c onto Cation-Exchange Chromatography Resins: Influence of Temperature on Retention

We studied the adsorption mechanism of two basic proteins, equine cytochrome c (Cyt) and chicken egg-white lysozyme (Lys), adsorbing onto negatively charged chromatography surfaces. In liquid chromatography, the retention volume of Lys was larger than that of Cyt on negatively charged ion-exchange resins. When the temperature increased, the retention volume of Cyt increased, whereas that of Lys clearly decreased. Both Lys and Cyt share similar physical characteristics, so the opposite behavior with increasing temperatures was surprising, indicating a more complex mechanism of adsorption may be involved. We analyzed the adsorption of these proteins by using isothermal titration calorimetry (ITC). The change in adsorption enthalpy determined by ITC allowed the understanding of the reason for and underlying driving forces of protein adsorption that resulted in this opposite behavior. Large exothermic enthalpies of adsorption were observed for Lys (-43.95 kJ/mol), and Lys adsorption was found to be enthalpically driven. On the other hand, endothermic enthalpies were dominant for Cyt adsorption (32.41 kJ/mol), which was entropically driven. These results indicate that dehydration and release of counterions play a more important role in Cyt adsorption and ionic interaction and hydrogen bridges are more significant in Lys adsorption. Understanding of the adsorption mechanism of proteins onto chromatography resins is essential for modeling and developing new, efficient chromatographic processes.

Characteristics of IgG subclasses and complement deposition in BP230-type bullous pemphigoid

BACKGROUND

Bullous pemphigoid (BP) is the most common autoimmune blistering disease. BP180 is the primary autoantigen of BP, and in a portion of BP cases, BP230 is the only target of autoantibodies. Such BP is called BP230-type BP. BP230-type BP tends to show milder clinical phenotypes than conventional BP, but the reason is unclear. The pathogenic roles of autoantibodies and complement activation have been shown in conventional BP, but the distribution of IgG subclasses and the degree of complement deposition in BP230-type BP remain unclear.

OBJECTIVE

To compare the distribution of IgG subclasses and the degree of complement deposition in BP230-type BP with those in conventional BP with autoantibodies to BP180 and BP230 (BP180-BP230-type BP).

METHODS

The diagnosis of BP was confirmed by the histopathology of the lesions, the deposition of IgG and complement in the perilesional skin and the presence of circulating autoantibodies to BP180 and BP230. The disease severity was determined by bullous pemphigoid disease area index. The deposition of IgG subclasses and complement deposition were examined by direct immunofluorescence of the perilesional skin in 6 BP230-type BP cases and 11 BP180-BP230-type BP cases.

RESULTS

Sixty seven percent of BP230-type BP cases show a mild clinical phenotype. All BP230-type BP cases and 82% of BP180-BP230-type BP cases were found to demonstrate the clear deposition of IgG4 at the basement membrane zone of skin specimens. Notably, the deposition of IgG1 and IgG3 was faint or negative in all of the BP230-type BP cases, whereas they were clearly detected in 91% and 64% of the BP180-BP230-type BP cases, respectively. The deposition of complement C3 tended to be weaker in BP230-type BP than in BP180-BP230-type BP.

CONCLUSION

The mild clinical phenotype of BP230-type BP may correlate with the weaker deposition of IgG1, IgG3 and complement in the skin lesions.

Retention Mechanism of Proteins in Hydroxyapatite Chromatography - Multimodal Interaction Based Protein Separations: A Model Study

BACKGROUND

Retention mechanism of proteins in hydroxyapatite chromatography (HAC) was investigated by linear gradient elution experiments (LGE).

MATERIALS AND METHODS

Several mobile phase (buffer) solution strategies and solutes were evaluated in order to probe the relative contributions of two adsorption sites of hydroxyapatite (HA) particles, C-site due to Ca (metal affinity) and P-site due to PO4 (cation-exchange). When P-site was blocked, two basic proteins, lysozyme (Lys) and ribonuclease A(RNase), were not retained whereas cytochrome C(Cyt C) and lactoferrin (LF) were retained and also retention of acidic proteins became stronger as the repulsion due to P-site was eliminated. The number of the binding site B values determined from LGE also increased, which also showed reduction of repulsion forces.

CONCLUSION

The selectivity (retention) of four basic proteins (RNase, Lys, Cyt C, LF) in HAC was different from that in ion-exchange chromatography. Moreover, it was possible to tune the selectivity by using NaCl gradient.

Reaction-Mediated Desorption of Macromolecules: Novel Phenomenon Enabling Simultaneous Reaction and Separation

Combining chemical reaction with separation offers several advantages. In this work possibility to induce spontaneous desorption of adsorbed macromolecules, once being PEGylated, through adjustment of the reagent composition is investigated. Bovine serum albumin (BSA) and activated oligonucleotide, 9T, are used as the test molecules and 20 kDa linear activated PEG is used for their PEGylation. BSA solid-phase PEGylation is performed on Q Sepharose HP. Distribution coefficient of BSA and PEG-BSA as a function of NaCl is determined using linear gradient elution (LGE) experiments and Yamamoto model. According to the distribution coefficient the selectivity between BSA and PEG - BSA of around 15 is adjusted by using NaCl. Spontaneous desorption of PEG - BSA is detected with no presence of BSA. However, due to a rather low selectivity, also desorption of BSA occurred at high elution volume. A similar procedure is applied for activated 9T oligonucleotide, this time using monolithic CIM QA disk monolithic column for adsorption. Selectivity of over 2000 is obtained by proper adjustment of PEG reagent composition. High selectivity enables spontaneous desorption of PEG-9T without any desorption of activated 9T. Both experiments demonstrates that reaction-mediated desorption of macromolecules is possible when the reaction conditions are properly tuned.

A simple method for calculating the productivity of polyphenol separations by polymer-based chromatography

A simple method for calculating the productivity of chromatography processes was proposed based on the iso-resolution curve concept. The model separation system was polyphenol separations by polystyrene divinylbenzene resins with the ethanol–water mixture mobile phase. The distribution coefficient K was determined as a function of ethanol concentration I by linear gradient elution experiments. The HETP-mobile phase velocity u curves were determined as a function of I. Using K and HETP, the iso-resolution curve was calculated, from which the productivity was determined as a function of I. It was found that there is an optimum I, where the highest productivity with the minimum amount of mobile phase consumption is obtained.

Relationship between the mobility of phosphocholine headgroup and the protein-liposome interaction: a dielectric spectroscopic study

Proteins could affect the headgroup mobility of phospholipid within liposome membranes through the protein-liposome interaction. The variation of headgroup mobility of phospholipid was then investigated by using the dielectric dispersion analysis. The eight proteins (Mw = 4.2-28.7 kDa) were used to investigate the protein-liposome interaction. It has been revealed that the strength of the protein-liposome interaction at 25 °C was linearly correlated with the stability of intramolecular hydrogen bondings of proteins, better than with their hydrophobicity and the surface charge density. Overall, liposomes composed of binary lipid system, appeared to strongly interact with proteins, in contrast to liposomes composed of single, ternary, and quaternary lipid systems. This is probably because liposomes composed of binary lipid system favored to form the microscopic environment where proteins could interact. The present result suggested the heterogeneous phase state of lipid membranes was one of dominant factors for the interaction between proteins and lipid membranes.

Abstract P5-13-07: Genetic polymorphism of estrogen metabolizing enzyme CYP17A1 rs743572 impacts on serum testosterone level in Japanese premenopausal women

The incidence of breast cancer in Japanese women has doubled in all age groups over the past two decades. We recently demonstrated that this marked increase is mostly due to an increase in the estrogen receptor (ER)-positive subtype, and we created risk prediction models for ER-positive breast cancer in both pre- and post- menopausal women using genetic factors (single nucleotide polymorphism (SNP)), environmental risk factors, serum hormones and growth factors by logistic regression analysis. Serum level of testosterone, which is the precursor of estradiol in estradiol synthesis, was found to be a risk predictor in both pre- and post- menopausal women. On the other hand, it has been reported that some SNPs, including those of estrogen-related genes such as ESR1 and CYP17A1, are correlated with breast cancer risk by genome-wide association studies. To acquire some insights into this mechanism, we analyzed genetic factors (14 SNPs), serum hormones and growth factors (estradiol, testosterone, prolactin, insulin-like growth factor 1 (IGF1) and IGF binding protein 3 (IGFBP3)) in 913 women with breast cancer and 278 disease-free controls for correlation between them.

Serum testosterone and prolactin levels were significantly higher in ER-positive breast cancer patients than in disease-free controls in both pre- (p&lt;0.0001, p&lt;0.0001) and post- (p&lt;0.0001, p = 0.007) menopausal women, and serum estradiol level was significantly higher in ER-positive breast cancer patients than in disease-free controls only in premenopausal women (p = 0.0005). There were significant differences in serum hormone levels among the women with each SNP genotype (homozygotes of major allele, heterozygotes and homozygotes of minor allele), including testosterone among rs743572 genotype (p = 0.014), estradiol among rs827421 genotype (p = 0.016), IGF-1 among rs6905370 genotype (p = 0.032), and prolactin among rs1042522 genotype (p = 0.035) in premenopausal women, as well as estradiol among rs3803662 genotype (p = 0.027) and IGFBP3 among rs6905370 genotype (p = 0.036) in postmenopausal women. In particular, serum testosterone level was significantly different among the rs743572, which is one of the enzymes that convert testosterone to estradiol, of genotypes (AA: 0.308 +/- 0.180 ng/ml, AG: 0.319 +/- 0.193 ng/ml and GG: 0.380 +/- 0.187 ng/ml, p = 0.014). On the other hand, the rs743572 heterozygotes of CYP17A1 have been reported to have increased breast cancer risk than homozygotes of both the major allele and minor allele in premenopausal women. Further studies are required to clarify this mechanism.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P5-13-07.

Abstract P5-05-04: Relationship between plasma estradiol levels and estrogen-regulated gene expressions in premenopausal estrogen receptor-positive breast cancers

Background: Estrogen receptor (ER) and progesterone receptor (PgR) expression status in breast cancer are important factors in determining the use of adjuvant therapy. Plasma estradiol (E2) and progesterone vary markedly through the menstrual cycle. Recently, the levels of PgR expression were reported to be correlated with E2 at the time of surgery in Caucasian premenopausal breast cancer patients. Materials and methods: In this study, plasma E2 levels at surgery were examined for correlations with expressions of estrogen-regulated genes (ERGs), including PgR, and proliferation genes in 147 Japanese premenopausal ER-positive breast cancers. Plasma E2 and progesterone, FSH, and LH were measured on the day of surgery by ECLIA and mRNA expressions were analyzed for 4 ERGs (PgR, GREB1, TFF1, PDZK1), 2 progesterone-regulated (RANKL, cyclin D1) and 2 proliferation genes (MKI67, BIRC5) by RT-PCR using the TaqMan system. ER and PgR protein expression levels were estimated by immunohistochemistry. Results: Our results revealed that expressions of PgR mRNA and protein in breast cancer tissues were significantly correlated with plasma E2 levels at surgery (p = 0.005, p = 0.0165, respectively). Other ERGs were also significantly correlated with plasma E2 levels. However, there were no correlations between mRNA expressions of proliferation genes, MKI67 and BIRC5, and plasma E2 levels. Furthermore, mRNA expressions of the progesterone-regulated genes, RANKL and cyclin D1, were significantly correlated with PgR mRNA expression (p&lt;0.0001, p&lt;0.0001, respectively). Discussion: Significant correlations were seen in the expression of ERGs in Japanese ER-positive breast cancers according to the plasma E2 levels, which vary markedly through the menstrual cycle. Our results supported the previous report in Caucasian patients by other group. This variability may affect the interpretation of gene expression profiles incorporating ERGs such as the 21-gene recurrence score.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P5-05-04.

Thrombus-targeted perfluorocarbon-containing liposomal bubbles for enhancement of ultrasonic thrombolysis: in vitro and in vivo study

BACKGROUND

External low-frequency ultrasound (USD) in combination with microbubbles has been reported to recanalize thrombotically occluded arteries in animal models.

OBJECTIVE

The purpose of this study was to examine the enhancing effect of thrombus-targeted bubble liposomes (BLs) developed for fresh thrombus imaging during ultrasonic thrombolysis.

METHODS

In vitro: after the administration of thrombus-targeted BLs or non-targeted BLs, the clot was exposed to low-frequency (27 kHz) USD for 5 min. In vivo: Rabbit iliofemoral arteries were thrombotically occluded, and an intravenous injection of either targeted BLs (n = 22) or non-targeted BLs (n = 22) was delivered. External low-frequency USD (low intensity, 1.4 W cm(-2) , to 12 arteries, and high intensity, 4.0 W cm(-2) , to 10 arteries, for both the targeted BL group and the non-targeted BL group) was applied to the thrombotically occluded arteries for 60 min. In another 10 rabbits, recombinant tissue-type plasminogen activator (rt-PA) was intravenously administered.

RESULTS

In vitro: the weight reduction rate of the clot with targeted BLs was significantly higher than that of the clot with non-targeted BLs. In vivo: TIMI grade 3 flow was present in a significantly higher number of rabbits with USD and targeted BLs than rabbits with USD and non-targeted BLs, or with rt-PA monotherapy. High-intensity USD exposure with targeted BLs achieved arterial recanalization in 90% of arteries, and the time to reperfusion was shorter than with rt-PA treatment (targeted BLs, 16.7 ± 5.0 min; rt-PA, 41.3 ± 14.4 min).

CONCLUSIONS

Thrombus-targeted BLs developed for USD thrombus imaging enhance ultrasonic disruption of thrombus both in vitro and in vivo.

Abstract P4-12-06: A mammographic density prediction model using environmental factors, endogenous hormones and growth factors in Japanese women

The incidence of breast cancer in Japanese women has doubled in all age groups over the past two decades, making it important to evaluate breast cancer risk factors in Japanese women. It is well known that mammographic density is positively associated with breast cancer risk in Western countries, and mammographic density is known to be affected by some environmental factors, serum hormones, and growth factors. We performed stepwise variable selection in a multiple regression model with fifteen independent variables as described below, based on the Akaike information criteria (AIC) to build a mammographic density prediction model using a dataset of 1191 women (913 women with breast cancer and 278 disease-free controls). The variables included were: environmental risk factors (body-mass index (BMI), age at menarche, pregnancy, age at first birth, breastfeeding, family history of breast cancer, age at menopause, use of hormone replacement therapy, alcohol intake and smoking), serum hormones and growth factors (estradiol, testosterone, prolactin, insulin-like growth factor 1 (IGF1) and IGF binding protein 3 (IGFBP3)) and mammographic density. The resulting prediction model is:

Mammographic density = + 0.000476 (IGF1) −0.0605 (testosterone) − 0.0508 (IGFBP3) − 0.00683 (age) − 0.0175 (BMI) + 0.00883 (age at menarche) − 0.0153 (breast feeding), (R2 = 0.336).

In this model, IGF1, testosterone, IGFBP3, age, BMI, age at menarche, and breastfeeding were considered to be important factors. IGF1 and age at menarche were positively associated with mammographic density, while on the other hand testosterone, IGFBP3, age, BMI, and breast feeding were negatively associated with mammographic density. Further studies are required to build a modified model incorporating serial measurements of serum hormones and growth factors to take into account time-dependent changes of serum hormones and growth factors, and to assess its accuracy.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P4-12-06.

PEGylated protein separations: challenges and opportunities

PEGylation, the covalent attachment of polyethylene glycol (PEG) chains to protein, isa promising method for making an efficient protein drug. Several PEGylated protein drugs, such as PEGylated interferons, are already on the market and others are presently in their clinical trials. However, the PEGylation reaction is very product specific so that generalized or platform processes for both reaction and purification have not yet been established. In the current issue of Biotechnology Journal, Günter Allmaier and colleagues report a modified microchip capillary gel electrophoresis (MCGE), which allows for a rapid separation (one minute) of PEGylated proteins of different degrees of PEGylation.

P4-10-11: Genetic and Environmental Predictors, Endogenous Hormones and Growth Factors and Risk of Estrogen Receptor-Positive Breast Cancer in Japanese Women

The incidence of breast cancer in Japanese women has doubled in all age groups over the past two decades. We have recently demonstrated that this marked increase is mostly due to an increase in the estrogen receptor (ER)-positive subtype. It is necessary to establish risk factors capable of predicting the risk of ER-positive breast cancer which will enable the efficient selection of candidates for preventive chemotherapy. We analyzed genetic factors, including 14 single nucleotide polymorphisms (SNPs), environmental risk factors (body-mass index (BMI), age at menarche, pregnancy, age at first birth, breastfeeding, family history of breast cancer, age at menopause, use of hormone replacement therapy, alcohol intake and smoking), serum hormones and growth factors (estradiol, testosterone, prolactin, insulin-like growth factor 1 (IGF1) and IGF binding protein 3 (IGFBP3)) and mammographic density in 913 women with breast cancer and 278 disease-free controls. To identify important risk factors, risk prediction models for ER-positive breast cancer in both pre- and postmenopausal women were created by logistic regression analysis. In premenopausal women, 1 SNP (CYP19A1-rs10046), age, pregnancy, breastfeeding, alcohol intake, serum levels of prolactin, testosterone and IGFBP3 were considered to be risk predictors. In postmenopausal women, 1 SNP (TP53-rs1042522), age, BMI, age at menopause, serum levels of testosterone and IGF1 were identified as risk predictors. Risk factors may differ between women of different menopausal status, and inclusion of common genetic variants and serum hormone measurements as well as environmental factors might improve risk assessment models. Further validation studies will clarify appropriate risk groups for preventive chemotherapy.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P4-10-11.

P3-03-01: Low Expression of microRNA-210 Is an Independent Good Prognostic Factor in Japanese Triple-Negative Breast Cancer Patients

Background: microRNAs (miRNAs) have emerged as a new class of non-coding genes involved in regulating cell proliferation, differentiation, and viability. Recent studies have identified miR-210 among a set of hypoxia-regulated miRNAs and demonstrated a direct regulatory role of hypoxia-inducible factor-1 alpha (HIF-1 a) in its transcription. High expression of miR-210 has been reported to be a poor prognostic factor in several types of cancers including breast.

Materials and Methods: TaqMan MicroRNA assays for miR-210 expression were performed in 219 breast cancers (58 triple-negative (TNBCs), and 161 ER-positive and HER2−negative). Correlations between miR-210 expression and clinicopathological factors were analyzed. The effects of several variables on survival were tested by Cox proportional hazards regression analysis.

Results: miR-210 expression in TNBCs was significantly higher than in ER-positive and HER2−negative breast cancers (p&lt;0.001). Patients whose TNBCs had low miR-210 expression experienced significantly better disease-free and overall survival compared with high miR-210 expressors (p=0.02 and p=0.05, respectively). Notably, among 40 node-negative TNBCs, 5-year disease-free survival was approximately 60% in patients whose tumors had high or intermediate miR-210 expression (n=26), while no patients with low miR-210 expression (n=14) suffered recurrent disease. Cox univariate and multivariate analyses demonstrated that low expression of miR-210 was an independent good prognostic factor in TNBCs.

Abstract P3-13-05: Estrogen Receptor-Positive Breast Cancer in Japanese Women: Trends in Incidence, Characteristics and Prognosis

Background: The incidence of breast cancer in Japanese women has doubled in all age groups over the past two decades. Patients and Methods: We examined the characteristics of patients and tumors treated in three time periods between 1982 and 2010. Estrogen receptor (ER), progesterone receptor (PgR), and HER2 status were assessed by immunohistochemistry. Correlation of hormone receptor levels with clinicopathological factors and prognosis was analyzed in ER-positive, HER2-negative breast cancer in two age groups (≥50 years vs. &gt;50 years).

Results: A total of 1903 women with breast cancer, who were treated at Nagoya City University Hospital, were included in this study. The frequency of ER-positive breast cancer in women aged 50 years or younger increased greatly over the interval studied (1982-1991: 52.5%, 1992-2001: 72.6%, 2002-2010: 87.1%, P &lt; 0.0001). The frequency of ER-positive tumors was also significantly increased in women over 50 years of age (1982-1991: 69.4%, 1992-2001: 73.3%, 2002-2010: 78.6%, P = 0.029). In ER-positive, HER2-negative breast cancer, tumor grade was negatively correlated with expression levels of ER (P = 0.0029) and PgR (P &lt; 0.0001). Interestingly, PgR levels were significantly higher in women aged 50 years or younger than in women over 50 years old (P &lt; 0.0001). In both age groups, the prognosis for patients with ER-positive, HER2- negative breast cancer significantly improved over time, due to advances in adjuvant therapies. ER and PgR expression levels were not associated with disease-free survival. Lymph node status and tumor size were strong prognostic factors regardless of the biological characteristics of the tumors in ER-positive, HER2-negative breast cancer in both age groups. Conclusions: It is necessary to establish risk factors, both genetic and environmental, capable of predicting the risk of ER-positive breast cancer and thus enable the efficient selection of candidates for hormone receptor-targeted chemoprevention. Furthermore, new approach should be considered to improve survival for node-positive, ER-positive breast cancer.

Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P3-13-05.

Estrogen receptor-positive breast cancer in Japanese women: trends in incidence, characteristics, and prognosis

BACKGROUND

The incidence of breast cancer in Japanese women has doubled in all age groups over the past two decades.

PATIENTS AND METHODS

We examined the characteristics of the tumors treated in three time periods between 1982 and 2010. Estrogen receptor (ER), progesterone receptor (PgR) and HER2 status were assessed by immunohistochemistry. Correlation of hormone receptor levels with clinicopathological factors and prognosis was analyzed in ER-positive, HER2-negative breast cancer in two age groups (≤50 years versus >50 years).

RESULTS

The frequency of ER-positive breast cancer in women aged 50 years or younger increased greatly over the interval studied (1982-1991: 52.5%, 1992-2001: 72.6%, 2002-2010: 87.1%, P < 0.0001). The frequency of ER-positive tumors also significantly increased in women over 50 years of age (1982-1991: 69.4%, 1992-2001: 73.3%, 2002-2010: 78.6%, P = 0.029). In ER-positive, HER2-negative breast cancer, tumor grade was negatively correlated with expression levels of ER and PgR. Prognosis for patients with ER-positive, HER2-negative disease significantly improved over time, due to advances in adjuvant therapies.

CONCLUSION

It is necessary to establish risk factors, both genetic and environmental, capable of predicting the risk of ER-positive breast cancer and thus enable the efficient selection of candidates for hormone receptor-targeted chemoprevention.

Predictors of Response to Exemestane as Primary Endocrine Therapy in Estrogen Receptor-Positive Breast Cancer

Endocrine therapy is the most important treatment of choice for estrogen receptor-positive breast cancer. Potential mechanisms for resistance to endocrine therapy involve estrogen receptor (ER)-coregulatory proteins and cross-talk between ER and other growth factor-signaling networks. However, the factors and pathways responsible for endocrine therapy resistance, particularly resistance to aromatase inhibitors, have not been clearly established. Sixteen postmenopausal patients with ERΑ-positive primary breast cancer were treated daily with 25 mg of exemestane (an aromatase inhibitor) for 6 months. Expressions of ERΑ, ERΒ, progesterone receptor (PgR), androgen receptor (AR), AIB1, aromatase, EGFR, HER2, Ki67, cyclin D1, p53, Bcl2, Stat5 and IGFBP5, and phosphorylations of ERΑ serine (Ser) 118, ERΑ Ser167, Akt Ser473 and p44/42 MAPK threonine (Thr) 202/ tyrosine (Tyr) 204 were examined by immunohistochemistry on pretreatment tumor biopsies and posttreatment surgical specimens. Analyses were made to test for correlations with response to exemestane. Of the 16 patients, 7 responded and 9 retained stable disease. High-level expression of AIB1 and phosphorylation of Akt Ser473 were significantly associated with a better response to exemestane, suggesting that these factors could be considered as predictors of exemestane response. Expressions of ERΑ, ERΒ, PgR, aromatase, Ki67, cyclin D1 and p53, and phosphorylations of ERΑ Ser118, ERΑ Ser167 and p44/42 MAPK Thr202/Tyr204 were decreased, whereas expressions of Stat5 and IGFBP5 were increased in posttreatment specimens compared to the values in pretreatment biopsies. Thus, the analysis of factors involved in the estrogen-dependent growth-signaling pathways may be useful in identifying patients responsive to exemestane.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 2041.

Calcein permeation across phosphatidylcholine bilayer membrane: effects of membrane fluidity, liposome size, and immobilization

The permeation of calcein across the phospholipid bilayer membrane is a key phenomenon in the detection system using liposomes as a sensor unit. The behavior of the calcein release from the liposome was analyzed by a first-order kinetic to obtain the permeability coefficient, Ps [cm/s]. The Ps value for the neutral liposome, prepared by zwitterionic 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), was found to depend on both the diameter of liposome and the temperature. The membrane fluidity of the POPC liposome, evaluated by the hydrophobic probe, 1-(4-trimethyl-aminophenyl)-6-diphenyl-1,3,5-hexatriene, was also dependent on the liposome diameter and the temperature. The Ps values for various neutral liposomes under gel phase or liquid-crystalline phase were correlated with their membrane fluidity, although some data were a little scattered, possibly due to the lamellarity. It is therefore considered that the membrane fluidity dominates the permeability of calcein across the neutral phospholipid membrane. Based on the above results, the Ps value for liposomes immobilized on the solid surface is discussed.

Binding site and elution behavior of DNA and other large biomolecules in monolithic anion-exchange chromatography

Our previous study has shown that there is a good correlation between the number of charges of DNA (from trimer to 50-mer) and the number of binding sites B in electrostatic interaction chromatography (ion-exchange chromatography, IEC). It was also found that high salt (NaCl) concentration is needed to elute large DNAs (>0.6M). In this paper we further performed experiments with large DNAs (up to 95-mer polyT and polyA) and charged liposome particles of different sizes (ca. 30, 50 and 100 nm) with a monolithic anion-exchange disk in order to understand the binding and elution mechanism of very large charged biomolecules or particles. The peak salt (NaCl) concentration increased with increasing DNA length. However, above 50-mer DNAs the value did not increase significantly with DNA length (ca. 0.65-0.70 M). For liposome particles of different sizes the peak salt concentration (ca. 0.62 M) was similar and slightly lower than that for large DNAs (ca. 0.65-0.70 M). The binding site values (ca. 25-30) are smaller than those for large DNAs. When arginine was used as a mobile phase modulator, the elution position of polyA and polyT became very close whereas in NaCl gradient elution polyT appeared after polyA eluted. This was mainly due to suppression of hydrophobic interaction by arginine.