Phase I study of gemcitabine, docetaxel, and imatinib in refractory and relapsed solid tumors

e13538

Background: The combination of the tyrosine kinase inhibitor imatinib with cytotoxic chemotherapy targets multiple pathways of tumor progression. In a previous phase I study, the combination of gemcitabine and imatinib was tolerable and had broad activity. The maximally tolerated dose (MTD) was gemcitabine 1500 mg/m2/150 minute and imatinib 400 mg days 1–5, 8–12, and 15–19. Given the activity seen when combining gemcitabine and docetaxel in some solid tumors, this phase I trial studied the addition of docetaxel to gemcitabine/imatinib. Methods: Twenty patients with relapsed/refractory solid tumors were enrolled in this IRB-approved study at the Cancer Institute of New Jersey and University of Michigan. The mean age was 64, mean ECOG PS 1. Five patients had lung cancer; 5, sarcoma; 3 ampullary-biliary tumors; 2 mesothelioma and bladder, 3, other. Imatinib was administered at 400 mg daily on days 1–5, 8–12 and 15–19. Gemcitabine was started at 600 mg/m2 at the fixed dose infusion of 10 mg/min on days 3 and 10 and docetaxel at 30 mg/m2 on day 10. Results: Because of unexpectedly severe hematological toxicities seen with escalating either gemcitabine or docetaxel, the protocol was amended to eliminate days 15–19 of imatinib. The MTD is gemcitabine 600 mg/m2, on days 3 and 10, docetaxel 30 mg/m2 on day 10, and imatinib 400 mg PO given on days 1–5 and 8–12. The dose limiting toxicities were neutropenic fever, pleural and pericardial effusion after cycle 1 of chemotherapy. The best response achieved was stable disease at 6 cycles in one patient each with mesothelioma and non small cell lung cancer (NSCLC) at the MTD. Two other patients with NSCLC had stable disease at 4 cycles. Discussion: An unexpectedly low MTD for this triplet was identified, an outcome different from prior experience with the doublets gemcitabine/imatinib or gemcitabine/docetaxel where much higher dosages are tolerated. Our results suggest possible drug-drug interactions that amplify toxicities with little initial evidence of improved tumor control. Given the unexpectedly high toxicity of the combination of gemcitabine, docetaxel and imatinib at low dosages, further development of this regimen is not indicated.

[Table: see text]

Rationally designed treatment for solid tumors with MAPK pathway activation

2532

Background: Preclinical studies shed light to the mechanism conferring paclitaxel resistance in solid tumors with active Ras/Raf/Mitogen-Activated Protein Kinase (MAPK) pathway, and determined a molecular mechanism by which addition of the proteasome inhibitor bortezomib abrogated this resistance, enabling tumor regression in animals in vivo. Methods: A Phase I study was contacted to determine the MTD of paclitaxel and bortezomib combinatorial treatment. Sixteen patients with refractory solid tumors were treated with weekly paclitaxel and bortezomib. Six patients had NSCLC; 4, colon cancer; 2, pancreatic; 2, melanoma; 1, breast; 1, ovarian. Patients with baseline neuropathy greater than or equal to Grade 1 were excluded. The starting dose was 40 mg/m2 for paclitaxel and 0.7 mg/m2 for bortezomib. A modified continual reassessment method (MCRM) was used for dose escalation with 3-patient cohorts treated at each dose level. The Target Toxicity Level (probability of DLT at the MTD) was set at 25%. Maximum dose escalation was no more than 75% of the previous SED level, if no Grade 3 hematologic toxicity or DLT were observed. Otherwise, the maximum dose escalation was no more than 50% of the previous SED level. The process continued until SED changes were no more than 10% for two consecutive cohorts. Results: The MTD for the combinatorial treatment was reached at 60 mg/m2 paclitaxel and 1.0 mg/m2 bortezomib. Of 15 evaluable patients, 1 patient with paclitaxel-resistant NSCLC had PR and 5 patients (2, NSCLC; 1, pancreatic; 1, colon; 1, ovarian) had stable disease. Median TTP was 2.3 months (0.8 to 6 months). Three NSCLC patients achieved TTP longer than 5 months. The combination of paclitaxel and bortezomib was relatively well tolerated. Paclitaxel PK parameters are being determined, and paraffin-embedded tumor specimens are being evaluated for MAPK pathway activation by IHC for phospho-ERK. Results will be correlated with clinical response. Conclusions: The MTD for the proposed combinatorial treatment is 60 mg/m2 for paclitaxel and 1.0 mg/m2 for bortezomib, and is relatively well tolerated. Combination of paclitaxel with bortezomib is effective in taxane-resistant NSCLC, and worthy of further investigation.

No significant financial relationships to disclose.

Postsurgical drainage and the risk of breast cancer recurrence in Chinese breast cancer patients

e22234

Background: Clinical investigations suggest that while primary breast cancer surgical removal favorably modifiers the natural history of breast cancer. Postoperative drainage, a surgery-derived discharge after breast cancer surgery, reflecting some biological features of surgical stimulation, was assessed and explored its relationship with breast cancer recurrence in this study. Methods: A total of 1445 women undergoing surgery between Jan 1, 2000 and Dec31, 2002 in Cancer Hospital of Fudan University, Shanghai, China was retrospectively studied. Survival curves were performed with Kaplan-Meier method and the predictive value of postsurgical drainage was estimated using proportional Cox regression model. Conclusions: The larger drainage volume POD 1 is a useful marker, suggesting a greater stimulation to surgical treatment compared to the lower ones. Awareness of the relationship between early surgery-stimulated effects and harmful wound healing response might help to explore new strategies to block or deplete these harmful effects, resulting in improving patients' survival.

No significant financial relationships to disclose.

MGMT expression in low-grade gliomas

e13001

Background: To evaluate the expression of MGMT in low-grade gliomas, and explore the relationship between its expression and the histological type of the tumour and the corresponding MRI characteristics. Methods: We assessed 389 low-grade gliomas (182 astrocytomas, 145 oligoastrocytomas, 61 oligodendrocytomas) with immunohistochemistry staining. We also recorded the preoperational MRI criteria such as tumor volume on T2 image, enhancing volume, tumor location, and relationship with ventricles. Results: The expression of MGMT in astrocytomas, oligoastrocytomas, and oligocytomas were 1.67 ± 0.78, 1.41 ± 0.86,1.44 ± 0.78, respectively. Significant stronger expression of MGMT was observed in astrocytomas than oligoastrocytomas and oligodendrocytomas (t = 3.00, p = 0.03), but no significant difference was observed between the latter two (t = 0.28, p = 0.78). MGMT expression level was significantly correlated with the enhancing volume of the tumor (r = -0.605, p = 0.002), but did not correlate with the total tumor volume (p = 0.504). Conclusions: MGMT is more strongly expressed in tumors of solely astrocyte component, and its expression level is negatively correlated with the extent of blood-brain barrier disruption. This suggest that MGMT may contribute to the tumor resistance to radiotherapy and chemotherapy in low-grade gliomas.

No significant financial relationships to disclose.

Observation of reversed shear Alfvén eigenmodes between sawtooth crashes in the Alcator C-Mod tokamak

Groups of frequency chirping modes observed between sawtooth crashes in the Alcator C-Mod tokamak are interpreted as reversed shear Alfvén eigenmodes near the q=1 surface. These modes indicate that a reversed shear q profile is generated during the relaxation phase of the sawtooth cycle. Two important parameters, q_{min} and its radial position, are deduced from comparisons of measured density fluctuations with calculations from the ideal MHD code NOVA. These studies provide valuable constraints for further modeling of the sawtooth cycle.

Transmission of hepatitis C virus in an orthopedic hospital ward

Healthcare-associated infections with hepatitis C virus (HCV) hitherto have been observed mainly in hemodialysis settings as well as in hematology and oncology wards. In this communication, molecular and epidemiologic investigations to elucidate an HCV outbreak in an orthopedic ward are reported. One hundred and thirty-five patients hospitalized in the ward and 104 staff members were tested. In addition to extensive epidemiologic reviews and hygienic inspections, direct sequencing of HCV PCR fragments and phylogenetic analysis of more than 300 partial HCV sequences obtained by end-point limiting-dilution real-time PCR assay were carried out. Six patients were infected with very closely related HCV variants. Patient-to-patient spread of the virus was inferred to have started from one patient with previous HCV infection to the other five patients during their hospital stay. Inspections did not reveal substantial breaches in basic infection control practices and did not identify a specific activity that might have led to nosocomial transmission. As a result of the investigations, the hospital corrected the documentation of all medical and nursing activities undertaken in the ward, abandoned the use of all multidose saline and other medication vials, and included explicitly recommendations for the safe preparation and administration of injectable drugs into internal infection control guidelines. Thereafter, no further nosocomial transmissions of HCV have been recorded in the orthopedic ward. The events observed suggest that nosocomial transmission of HCV is not limited to hemodialysis, hematology or oncology settings, and they also reinforce the mandatory adherence to basic infection control practices.

Assessment of self-reported and health-related quality of life in patients with brain tumours using a modified questionnaire

Assessment of quality of life (QoL) in patients who undergo surgery for brain tumours helps to guide surgery, reduce recurrence and minimize morbidity. This study validated a 25-item, modified QoL questionnaire based on the Medical Outcomes Survey SF-36 and the Karnofsky Performance Scale. The aims were for it to be brain tumour specific for Chinese patients, hence more sensitive, more acceptable, briefer and more easily used. A total of 431 patients with brain tumours were compared with 96 age-matched healthy controls. A surgery-related QoL curve was used to help identify a threshold satisfaction point for QoL. Physiological function, psychological function, satisfaction with medical care and self-care ability of the patients were compared pre-operatively and post-operatively. Cronbach's alpha-coefficient was 0.9521 and the correlation coefficient was 0.8685, suggesting good reliability and repeatability. With the exception of psychological function, which deteriorated, the modified QoL showed significant improvement in physiological function, satisfaction with medical care and self-care ability, and serves to stress the importance of post-operative psychological support.

Application of Radiofrequency Ablation of Renal VX2Tumors by Cooled-Tip Electrode in a Rabbit Model

Objective. This study has two purposes: (a) to compare the use of tumor cell suspensions and excised tumor tissue for generating renal tumors suitable for radiofrequency ablation (RFA) studies and (b) to assess the efficacy of RFA for ablation of renal VX2 tumors in a rabbit model. Procedures. VX2 tumor masses were used to inoculate 17 rabbits. The renal VX2 tumors of 13 rabbits were subsequently treated with a cooled-tip RF system at a power of 15-30 W for 3-6 minutes, and 4 rabbits served as control. After RFA, rabbits were observed by contrast-enhanced CT to ascertain the ablative range. Rabbits were divided into three groups and sacrificed at 3, 7, and 14 days post-treatment for histopathological studies. Results. Both tumor implant methods had a 100% success rate in generating tumors. The average lesion produced was 1.3x1.8x1.5 cm. Complete tumor ablation occurred in 76.9%, and local tumor growth in 23.1%. Depending on the position of the tumors, the complications after RFA treatment included infarction, perirenal hematoma, hydronephrosis, and abscess. The over-all complication rate was 38.5%. In histopathological studies, a central needle track, tumor coagulation, renal tissue coagulation, peripheral hemorrhage, and an inflammatory layer could be observed. Conclusion and clinical relevance. Application of RFA to destroy renal VX2 tumors in this rabbit model has a relatively high cure rate. It can be used to destroy small renal tumors in a precise and non-invasive manner. Impact on human medicine. We hope to apply this procedure in selected human renal tumors in the future.

Validation and clinical interpretation of the St George's Respiratory Questionnaire among COPD patients, China

SETTING

Although the St George's Respiratory Questionnaires in Mandarin-Chinese (SGRQ-MC) have been used in China, few data are available on the translation and adaptation process, psychometric properties and clinical meaning. It is therefore difficult to adequately evaluate the equivalence of this instrument in Chinese populations.

OBJECTIVE

To evaluate the psychometric properties of a culturally translated SGRQ-MC, and to estimate clinically important differences (CID) for the SGRQ in chronic obstructive pulmonary disease (COPD) patients in China.

DESIGN

SGRQ was translated into Mandarin using standardised forward and backward translation procedures. Health status and clinical data were collected at baseline in 491 patients with stable COPD and again after 1 week in 131 randomly selected patients. All patients were followed up monthly and assessed during exacerbations and at 1 year.

RESULTS

The SGRQ-MC showed good internal consistency, test-retest reliability, convergent validity and known-group validity. Responsiveness was shown by significant changes in SGRQ-MC scores between stable stage and exacerbation (P<0.0001). The estimated CID for the total score ranged from 3.1 (95%CI -0.3-6.5) to 7.7 (95%CI -1.7-17.2).

CONCLUSION

This SGRQ-MC is a reliable, valid and responsive instrument for quality of life evaluation in COPD patients in China. As it is culturally and clinically equivalent to other versions, measures can be compared among countries.

Luminal group may give more benefit for invasive micropapillary carcinoma component breast cancer patients: experience from Cancer Hospital Fudan University

Abstract #6152

Objective: Comparative studies on clinical features and outcomes of very rare invasive micropapillary carcinoma of breast cancer of 4 subtypes by immunohistochemistry staining.&#x2028; Methods: From Aug 2005 to Mar 2008, a total of 52 breast cancer patients(BCPs) with an invasive micropapillary component (IMPC) among 1951 Chinese BCPs with complete of clinicopathologic data in our institution were enrolled into a retrospective analysis. We characterized all these 52 patients and analyzed using various parameters.&#x2028; Results: The 52 cases of breast carcinoma with an IMPC all occurred in women. Mean age was 51 years (range from 26-82). All of these patients had breast masses; one also had metastasis to the supraclavicular lymph node at the time of diagnosis., mean tumor size was 2.83cm(T2), 23.08%(12/52) was pure invasive micropapillary carcinoma, and lymph node positive percentage was 75.59 %( 36/51).Fifty one patients received surgery, while one of them lost the chance of surgery. Forty of them received the modified mastectomy while one was performed lumpectomy due to old age. One was performed LAND alone and four were performed lumpectomy and sentinel lymph node biopsy.&#x2028; By using IHC staining, when we regard HER2/neu 0 and +as negative. The Luminal A group, Luminal B, trip-negative, HER2+ /ER- were 76.92% (40/52), 11.54 %( 6/52), 7.69 %( 4/52), 3.85 %( 2/52), respectively. Compared to the database of 2005 breast cancer carcinoma in our institution, there was more Luminal A group patients than the whole group (P=0.01, chi-square test.), more Luminal B (P=0.028, Fisher exact possibility test), less trip-negative group (P=0.001, chi-square test). The positive lymph node among the Luminal A group, Luminal B, trip-negative, HER2+ /ER- were 65%,80%, 100%, 100%, respectively, while the lymphvascular invasion were 55%,33.33%,50%,50%,respectively, Mulifocality in Luminal A was 25% , 16.67% in Luminal B , while 50% in both trip-negative and HER2+/ER-.&#x2028; Twenty-one of them received both anthracyclines and Taxane, while 27 only received anthracyclines, Four patients only were received only AIs due to old age. All the luminal group patients received endrocine therapy after chemo. After nearly 14 months (2∼34 months) follow up, thirty-six women were disease free, one had local recurrence, and 1 had lung metastasis, while 1 had ovary carcinoma when the diagnosis of breast malignant, one patient lost following up due to mental disorder. Among the luminal B, one had metastasis when diagnosis, others were disease free. One woman of the trip-negative died of non-breast cancer disease,the HER2+/ER- group was no recurrence or metastasis.&#x2028; Discussion: The prelimary results showed that more luminal group in the IMPC may get benefit from the endocrine therapy. However the number of these cases is small and follow-up time is not very long, further studies are necessary to explain these rare and unique pattern of invasive carcinoma.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 6152.

Seroma formation after breast cancer surgery and its risk factors

Abstract #4085

Background:. Seroma formation is one of the most common complications after breast cancer surgery including modified radical mastectomy and breast conservative surgery. Our study aims to investigate the risk factors of postoperative seroma in Chinese breast cancer patients.&#x2028; Methods: Clinical data of 158 women who underwent surgerical therapy for breast cancer in our hospital were collected prospectively and all patients were followed up. The risk factors for seroma occurrence were compared between the seroma group and control group using X 2 test or t test, as well as the logistic regression was used as multivariate analysis.&#x2028; Results: Univariate analysis showed that the average age of the seroma group was significantly higher than those without seroma formation(58.71vs51.00, P=0.0019), but the total serum protein and albumin content were lower (68.47g/L vs 72.53g/L, P=0.009 and 40.75g/L vs 42.52g/L,P=0.020, respectively). In seroma group, the drainage volume of the first three days, the total and daily drainage volume were all higher (all p values less than 0.01), as well as drainage duration and hospital stay were longer(8.3d vs 14.4d, P=0.000 and 11.5d vs 23.7d, P=0.000, respectively). Logistic regression showed that older patients (OR=1.080, 95%CI 1.016∼1.148, P=0.013), lower total serum protein content(OR=0.814, 95%CI 0.705∼0.940, P=0.005)and higher drainage volume in d1(OR=1.009, 95%CI 1.001∼1.016, P=0.022) and d3 (OR=1.017, 95%CI 1.005∼1.029, P=0.005) were all independent risk factors for subcutaneous seroma. The daily average drainage curve showed a gradually decreasing trend with a highest collections in the first three days. The seroma group had significantly higher average daily drainage volume( P=0.034) and longer duration (P=0.000).&#x2028; Conclusion:The risk factors of seroma formation after breast cancer surgery are complicated. However in order to prevent its occurrence effectively, the factors including age, nutrition status and daily drainage volume should be taken into consideration.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 4085.

Clinicopathological features of the triple-negative tumors in Chinese breast cancer patients

Abstract #6080

Background: Triple negative breast cancers are defined by a lack of expression of estrogen, progesterone, and Her-2 receptors. A number of studies suggested that the triple-negative phenotype could contribute to an aggressive behavior and a poor prognosis. However, similar data is still not available for Chinese populations. We sought to analyze the clinicopathological features of this subgroup in our hospital in order to get characteristics for Chinese breast cancer.&#x2028; Methods: We performed a retrospective study of 2028 female unilateral breast cancer patients undergoing surgery in our hospital from February 1991 to December 2003. ER, PR and Her-2 status were assessed using immunohistochemical staining. Survival curves were performed with Kaplan-Meier method and annual recurrence hazard was estimated by hazard function.&#x2028; Results: According to different combinations of hormone receptor (HR) and Her-2 status, 2028 patients were categorized into the three subgroups as follows: Her-2+ (32.25%), HR+/Her-2- (48.92%) and triple-negative (18.83%). Triple-negative tumors were larger (greater than 2 cm in diameter) than HR+/Her-2- tumors, but smaller than Her-2+ tumors (70.03%, 66.15% and 76.15% respectively, P &lt; 0.001). In addition, 21.99% of patients whose tumors were triple-negative had four or more axillary nodes involved compared with 27.37% of patients with Her-2+ tumors and 22.78% with HR+/Her-2- tumors (P = 0.004). There were statistical differences in the distribution of TP53 mutation and Cathepsin-D status (P &lt; 0.001 for both). In the univariate analysis, we found a statistical significance for recurrence-free survival (RFS) among the three subgroups (P = 0.0036), with the rate of 72.89% for Her-2+ tumors, 78.26% for HR+/Her-2- tumors and 75.61% for triple-negative tumors at the 11th year respectively. When it came to the time of hazard peaks, discrepancies existed in different subgroups. Triple-negative patients showed an early major recurrence surge peaking at the 2.5th year after surgery, followed by a gradual decline until year 6.5 and then a modest increase. As to HR+/Her-2- patients, the hazard plot exhibited a wide initial plateau-like wave covering at least 4 years and a subsequent rise. The hazard rate for Her-2+ patients displayed a tapering sharp at the 1st year and a second rise. Furthermore, the first peak of triple-negative tumors was higher than that of HR+/Her-2- patients, but lower than that of Her-2+ ones.&#x2028; Conclusions: The recurrence pattern for triple-negative tumors was intermediate between Her-2+ and HR+/Her-2- counterparts.Our findings suggested that biological characteristics and prognosis of Chinese triple-negative breast cancer might be more favorable and somewhat different from those in Western populations.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 6080.

Circulating tumor cell and endothelial cell data from a phase II evaluation of lapatinib and bevacizumab in HER2-overexpressing metastatic breast cancer

Abstract #3154

Background: Overexpression of both HER2 and VEGF is associated with worse outcome than overexpression of either receptor alone. In preclinical models, combination anti-HER2 and anti-VEGF therapy has been shown to be more effective than either treatment alone. Bevacizumab (B) plus trastuzumab and lapatinib (L) plus pazopanib have shown activity in patients (pts) with HER2+ MBC. We evaluated the combination of L+B in a phase 2 trial in HER2+ MBC pts. To explore new biomarkers of treatment effect, we measured circulating tumor cells (CTCs) with two different methods of CTC enumeration: CellSearch (Veridex LLC), and immunomagnetic enrichment followed by flow cytometry (IE/FC), as well as circulating endothelial cells (CECs) in pts receiving study treatment.&#x2028; Methods: This study evaluated L (1500 mg PO daily) plus B (10 mg/kg IV q2wk) in 50 HER2+ MBC pts. The primary endpoint is crude progression-free survival (PFS) at 12 wks. Serial evaluation of CTC and CEC was performed. Blood was obtained from consenting pts at baseline, weeks 2, 6 then every 12 weeks until end of study. CellSearch assay was performed as previously described using 7.5 cc blood in a CellSave tube and the CellSpotter analyzer. For IE/FC, 20 ml of blood was subjected to IE using anti-EpCAM ferrofluid, followed by FC for EpCAM, CD45, and nucleic acid content. CTC data were correlated with assay method and with best response. CECs were defined as CD34/31+, CD45-, or CD34/146+, CD45-, and were assayed by FC.&#x2028; Results: Enrollment to this study ended in March 2008 (n=52). Clinical data is presented at this meeting (Dickler et al). 47 patients have evaluable CTC and CEC data at baseline and/or first follow-up; 32 patients have response data. CTC determined by CellSearch or IE/FC showed significant correlation at baseline (R=0.58; P=0.012). CTC by CellSearch at first followup correlated with treatment response (P=0.01) with levels above 5 CTC/sample associated with progression; there was no correlation with baseline values. There were too few positive IE/FC values to evaluate correlation with outcome. The change in CEC/CD146 from baseline to first followup for is of borderline significance in this preliminary analysis (P=0.07) between PR (N=2, Mean Change Score/MCS=-4.345) and SD/PD (N=18, MCS=0.8); a decrease of CEC/CD146 from baseline to first followup suggests greater likelihood of response.&#x2028; Conclusions: L+B is an active regimen in pts with MBC. CTC measurements correlated between two separate methodologies, and for the CellSearch assay predicted response to therapy. A decrease in CEC from baseline to first followup correlated with response to this combined targeted therapy, consistent with our previous results with other B-based therapy. PFS and response correlations for the full study cohort will be presented.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 3154.

Observation of ion-cyclotron-frequency mode-conversion flow drive in tokamak plasmas

Strong toroidal flow (Vphi) and poloidal flow (Vtheta) have been observed in D-3He plasmas with ion cyclotron range of frequencies (ICRF) mode-conversion (MC) heating on the Alcator C-Mod tokamak. The toroidal flow scales with the rf power Prf (up to 30 km/s per MW), and is significantly larger than that in ICRF minority heated plasmas at the same rf power or stored energy. The central Vphi responds to Prf faster than the outer regions, and the Vphi(r) profile is broadly peaked for r/a < or =0.5. Localized (0.3 < or = r/a < or =0.5) Vtheta appears when Prf > or =1.5 MW and increases with power (up to 0.7 km/s per MW). The experimental evidence together with numerical wave modeling suggests a local flow drive source due to the interaction between the MC ion cyclotron wave and 3He ions.

Cloning, sequence analysis, and expression of cDNA coding for the major house dust mite allergen, Der f 1, in Escherichia coli

Our objective was to clone, express and characterize adult Dermatophagoides farinae group 1 (Der f 1) allergens to further produce recombinant allergens for future clinical applications in order to eliminate side reactions from crude extracts of mites. Based on GenBank data, we designed primers and amplified the cDNA fragment coding for Der f 1 by nested-PCR. After purification and recovery, the cDNA fragment was cloned into the pMD19-T vector. The fragment was then sequenced, subcloned into the plasmid pET28a(+), expressed in Escherichia coli BL21 and identified by Western blotting. The cDNA coding for Der f 1 was cloned, sequenced and expressed successfully. Sequence analysis showed the presence of an open reading frame containing 966 bp that encodes a protein of 321 amino acids. Interestingly, homology analysis showed that the Der p 1 shared more than 87% identity in amino acid sequence with Eur m 1 but only 80% with Der f 1. Furthermore, phylogenetic analyses suggested that D. pteronyssinus was evolutionarily closer to Euroglyphus maynei than to D. farinae, even though D. pteronyssinus and D. farinae belong to the same Dermatophagoides genus. A total of three cysteine peptidase active sites were found in the predicted amino acid sequence, including 127-138 (QGGCGSCWAFSG), 267-277 (NYHAVNIVGYG) and 284-303 (YWIVRNSWDTTWGDSGYGYF). Moreover, secondary structure analysis revealed that Der f 1 contained an a helix (33.96%), an extended strand (17.13%), a ss turn (5.61%), and a random coil (43.30%). A simple three-dimensional model of this protein was constructed using a Swiss-model server. The cDNA coding for Der f 1 was cloned, sequenced and expressed successfully. Alignment and phylogenetic analysis suggests that D. pteronyssinus is evolutionarily more similar to E. maynei than to D. farinae.