Abstract P1-01-09: Which nomograms may be the best for predicting nonsentinel lymph node metastasis in breast cancer patients: a meta-analysis

Background: Axillary lymph node dissection (ALND) is the standard treatment for breast cancer patients with positive sentinel lymph nodes (SLNs). Several nomograms were developed to identify SLN-positive patients with low risk of nonsentinel lymph nodes (NSLNs) metastasis. These nomograms were validated in different populations and it is still unknown which is the best. This study is to present a systemic review and perform a meta-analysis to obtained the pooled AUC (Area Under the receiver-operator Curve) value of each models.

Methods: This review focused on six models: Cambridge, MSKCC, Mayo, MDA, Tenon and Stanford models. A “Pubmed” search and “Web of science” search were conducted and 35 literatures were ultimately included. AUC and the number of patients with positive NSLNs were extracted. Publication bias and heterogeneity were analyzed. AUCs were converted to odds ratios (ORs) for combination. The combined ORs were converted back to AUCs to represent the integrated discriminative capabilities of each models.

Findings: In total, the Cambridge, Mayo, MDA, MSKCC, Stanford and Tenon models were validated in 8, 6, 4, 39, 14 and 15 studies, with 2156, 2431, 843, 8143, 3700 and 3648 patients included, respectively. There were no publication bias or heterogeneity observed in the Cambridge, Mayo, MDA and Tenon models (Table 1). The combined ORs and the corresponding AUCs of each models were listed as follow: Cambridge (OR = 3.86, AUC = 0.71), Mayo (OR = 3.71, AUC = 0.71), MSKCC (OR = 3.47, AUC = 0.70), MDA(OR = 3.44, AUC = 0.70), Tenon (OR = 3.46, AUC = 0.70) and Stanford (OR = 2.92, AUC = 0.67). For each of the predictive models, both fixed and random effect models were used to calculate the combined OR. The presence of larger difference between the fixed and random effect analysis suggests small study effects, rendering the meta-analysis relatively less reliable. The combined ORs were identical when fixed and random effect models were used in the Cambridge and MDA models, suggesting that there was no small study effects in these two models.

P3-07-13: Validation and Comparison of Models To Predict Nonsentinel Lymph Node Metastasis in Chinese Breast Cancer Patients with Positive Sentinel Lymph Nodes

Background: Several models for predicting the risk of nonsentinel lymph node (NSLN) metastasis in breast cancer patients with positive sentinel lymph nodes (SLNs) have been developed. Independent validation of these models in different populations is necessary before clinical application. This study aimed to validate and compare these models in Chinese patients.

Patients and Methods: A total of 159 breast cancer patients with positive SLNs treated at our institution were included. Chi-squared tests, RP-ROC, CART and multivariate logistic regression were used to analyze the risk factors for NSLN involvement in our population. ROC curves, calibration plots and false-negative (FN) rates were evaluated for 11 reported models. The threshold of each model for classifying patients into the low-risk group was adjusted to render the FN rate close to 10%.

Results: In total, 81 (50.9%) patients had at least one NSLN involvement. Univariate and multivariate analyses revealed that the number of negative SLNs (P<0.01, HR=0.63) and the metastasis size of the positive SLNs (P<0.01, HR=1.15) independently predicted the NSLN status in our population. The Cambridge and Mou models outperformed the others, both with AUCs of 0.73. The other models performed as follows: the Mayo, Tenon, MDA, MSKCC, Ljubljana, SNUH and Louisville models had AUCs of 0.68, 0.66, 0.66, 0.64, 0.62, 0.61 and 0.60, respectively. The Stanford and Saidi models did not present any discriminative capabilities, with AUCs of 0.54 and 0.50, respectively. The Cambridge, MSKCC and Mayo models were well calibrated. The Ljubljana model did not calibrate well.

Ipr1 gene mediates RAW 264.7 macrophage cell line resistance to Mycobacterium bovis

Tuberculosis caused by Mycobacterium bovis (M. bovis) seriously affects efficiency of animal production with impacts on public health as well. Effective programmes of prevention and eradication of M. bovis infection therefore are urgently needed. Intracellular pathogen resistance gene 1 (Ipr1) is well known to mediate innate immunity to Mycobacterium tuberculosis (MTB), but there are no reports as to whether Ipr1 can enhance the phagocytic ability of macrophage against M. bovis. In this investigation, RAW 264.7 macrophage was transduced with lentiviral vector carrying Ipr1 (named Lenti-Ipr1); transgenic cells were identified by RT-PCR and western blotting. Transgenic positive cells (R-Ipr1) were then infected with an M. bovis virulent strain, with non-transduced cells used as control. When cell proliferation, viability and apoptosis of the two groups were investigated, it was found that infected RAW 264.7 died by necrosis whereas R-Ipr1 underwent apoptosis. Furthermore, the numbers of intracellular bacteria in R-Ipr1 were lower than those in control cells (P < 0.05). To identify the role of Ipr1, we measured the genes of Casp3, Mcl-1 and NOS2A which associated with macrophage activation and apoptosis by real-time quantitative PCR. The results demonstrated that Ipr1 gene expression can enhance anti-M. bovis infection of macrophage. This establishes a basis for the future production of Ipr1-transgenic cattle to strengthen the tuberculosis resistance.

Mir-30 reduction maintains self-renewal and inhibits apoptosis in breast tumor-initiating cells

Accumulating evidence indicates that a sub-population of cancer cells with stem-like properties, termed tumor-initiating cells (T-ICs), exist in many different kinds of malignancies, which have a pivotal role in tumorigenesis, tumor progression, metastasis and post-treatment relapse. However, how the stem-like properties of T-ICs are regulated remains obscure. Our previous study showed that reduction of let-7 microRNA (miRNA) in breast tumor-initiating cells (BT-ICs) contributes to the maintenance of their self-renewal capacity and undifferentiated status. In this study we show the effect of mir-30 reduction on the stem-like features of BT-ICs. Similar to let-7, mir-30 is reduced in BT-ICs, and the protein level of Ubc9 (ubiquitin-conjugating enzyme 9) and ITGB3 (integrin beta3), the target genes of mir-30, is markedly upregulated. Enforced constitutive expression of mir-30 in BT-ICs inhibits their self-renewal capacity by reducing Ubc9, and induces apoptosis through silencing ITGB3. On the contrary, blocking the miRNA with a specific antisense oligonucleotide (ASO) in differentiated breast cancer cells revived their self-renewal capacity. Furthermore, ectopic expression of mir-30 in BT-IC xenografts reduces tumorigenesis and lung metastasis in nonobese diabetic/severe combined immunodeficient mice, whereas blocking mir-30 expression enhances tumorigenesis and metastasis. Together, our data suggest mir-30 as one of the important miRNAs in regulating the stem-like features of T-ICs.

Let-7 Inverts the Chemoresistance of Breast Tumor-Initiating Cells

Background: Cancers may arise from rare self-renewing highly tumorigenic “stem” cells, which are thought not only to be the source of the tumor, but also to be responsible for resistance to cancer therapy and subsequent tumor recurrence. Our preliminary data strongly suggest that let-7 is a master regulator of BT-IC self-renewal and multipotency. It is likely that let-7 regulates many other genes/pathways during BT-IC differentiation. However, we do not know whether let-7 might also regulate other putative aspects of “stemness” such as chemoresistance.Material and Methods: Quantified qRT-PCR was used to test the expression of let-7a in chemoresistant breast tumor tissue from patients, as well as the chemosensitive samples. The location of let-7a in primary breast cancer samples from patients with chemoresistance were compared to the samples without chemoresistance by in situ hybridization analysis.SK-3rd Cells, which is a cell line enriched in breast tumor-initiating cells, were cultured in suspension to form mammosphere which could be induced to differentiation with adhesive culture. Lentivirus-mediated let-7a transduction was used to increase the expression level of let-7a.Let-7 target gene expression (HRAS and HMGA2) was determined by qRT-PCR and western blot. The response of BT-ICs to chemotherapy was determined by MTT, Annexin V and Tunel.Results: The expression level of let-7a microRNA in chemoresistant patients were significantly lower than the patients without chemoresistance (P&lt;0.05). The let-7a mimics can effectively enhance the expression of let-7a in mammospheric SK-3rd cells, and reduced the expression level of H-RAS and HMGA2 proteins, which are the targets of let-7. Mammospheric SK-3rd cells tranfected with let-7a mimics had a lower proliferation rate and a higher apoptosis rate under epirubicin treatment.Conclusion: Lack of expression of let-7 regulates BT-IC resistance to chemotherapy. Therefore, let-7a may be an effective maker to predict the response of tumor to chemotherapy.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 1136.

Proportion of Tumor Initiating Cells Contributes to Chemotherapeutic Resistance of Breast Cancers

Background: The mechanisms determining chemotherapeutic resistance of breast cancers are rather complicated with a variety of molecules involved. While targeting one single molecule or one signaling pathway are not sufficient to reverse chemo-resistance. Therefore, it is more important to identify and eliminate the subpopulations of tumor cells that are resistant to chemotherapy. Recently, accumulating evidence demonstrates that a wide variety of malignancies may be driven by a small subset of “tumor-initiating cells (T-ICs) displays a variety of drug-resisting mechanisms. Nevertheless, it remains obscure whether the proportion of breast tumor initiating cells (BT-ICs) correlates with chemotherapeutic sensitivity of breast cancers, and whether targeting BT-ICs may help to reverse chemo-resistance in the malignancy.Material and Methods: Using immunohistochemistry, we tested the expression level of ALDH1 in 192 human breast cancer samples before underwent neoadjuvant chemotherapy and analyzed the relationship between the ALDH1 level and clinical pathological features including clinical response and disease free survival (DFS). We tested the proportion of CD44+/CD24-, ALDH1+ and side population in primary cancer cells, wide type MCF7 and Adriamycin resistant (AdrR) MCF-7 by FACS. Compared the mammosphere formations in suspension culture. We further tested the drug sensitivity after treated with 1UM Lapatinib in AdrR MCF-7 mammospheric cells by MTT and AnnexinV staining. Results: In all 192 cases, there were 19.79% (38 of 192) cases with high ALDH1 expression (&gt;20% positive cancer cells) compared to 80.21% (154 of 192) cases with low expression (≤20% positives cells). The clinical response (PR and cCR) was only 52.63%% (20 of 38) in patients with high ALDH1 expression compared with 81.17% (125 of 154) in patients with low ALDH1 expression (x2=15.926; P=0.000). Patients with low ALDH1expression survived significantly longer than those with high ALDH1 expression (P = 0.006). In primary cancer cells, the percentage of ALDH1+ and CD44+/CD24-cells were up to 8.72% ±3.73% and 36% ±7.9% in the PD samples respectively, whereas only 1.42%±1.63% and 3.17 ±0.45% in PR samples (p=0.037 and 0.018). Moreover, mammosphere formation of primary human breast cancer cells was 10-20 fold higher in PD samples than in PR samples (p=0.01). Then we compared the proportion of BT-ICs between two breast cancer cell lines. The mammoshpere formation rate of the AdrR MCF-7 increased to 9.1%±1.01% compared with 1.03%±0.15% in the parent MCF-7 breast cancer cell (p=0.0046), meanwhile, the percentage of CD44+/CD24- cells was much higher in the AdrR MCF-7 cells(64.85%±1.3% vs than 1.3%±0.1%,p=0.01), the proportion of ALDH1+ cells was 15.9%±1.5% to 2.7%±0.3% (p=0.01),as well as the percentage of side population was 10.8%±1.4% to.0.25%±0.05% (p=0.001).After treated with Lapatinib, the sensitivity of passaged mammospheric AdrR MCF-7 cells to chemotherapy increased in the cell viability assay, while the dead cells increased from 50% ±2.8% to 75%±6.5% tested by FACS under chemotherapy pressure (p=012).Conclusion: Proportion of tumor initiating cells contributes to chemotherapeutic resistance of breast cancers.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 503.

China Validation Study of GeneSearchTM Breast Lymph Node Assay for the Diagnosis of Sentinel Lymph Nodes of Breast Cancer – CBCSG-001a Interim Results

Background: The use of sentinel lymph node (SLN) biopsy is becoming the standard of care in China. With the adoption of this technique there is an increasing need for rapid and accurate detection of metastases in the SLNs. Histological intra-operative techniques such as touch imprint and frozen section offer limited sensitivity, increasing the risk of intra-operatively missing relevant SLN metastases (&gt;0.2 mm). Post-operative histology (H&E) also risks missing metastases due to tissue sampling limitations and being partially dependent on pathologist expertise. A real-time RT-PCR assay, GeneSearchÔ Breast Lymph Node (BLN) Assay, may offer a standardized intra-operative way to evaluate larger portions of the SLN. CBCSG-001a is a prospective multicenter trial to validate the GeneSearchÔ BLN Assay in China.Methods: Started from February 2009, CBCSG-001a is being conducted at 6 centers with a total enrollment of 540 cases by the end of June 2009. SLNs are cut into alternating ∼2mm sections. One half of the sections are sampled for H&E. The other half is fully tested with the BLN assay. The assay detects the presence of cytokeratin-19 and mammaglobin to assess if metastases are in SLNS. Predetermined cutoffs are calibrated so only metastases &gt;0.2 mm are detected. Each assay run has internal and external controls to confirm a valid result.About 40% cases would receive axillary lymph node dissection (ALND) in spite of the status of SLN in 3 of the 6 centers. Intraoperative frozen section for SLN diagnosis was conducted in 4 of the 6 centers, and intraoperative touch imprint cytological diagnosis for all sections was conduced in 2 of the 6 centers.Results: Interim results are based on 20% (114/540) of the planned breast cancer patients for the study. Current histology positive rate is 30%. The BLN assay shows high performance as compared to H&E. The results are also very similar to those seen in the larger US clinical validation trial.Discussion: Interim results indicate that the BLN assay has high performance as compared to H&E, and allows same surgery ALND avoiding the need to wait for a second surgery. In addition the performance is equivalent to the results seen in the larger US clinical validation trial, indicating the assay performance is fairly robust. So there is clinical potential of using the assay for performance similar to H&E with the advantage of being an intra-operative, objective and standardized test that examines a larger portion on the nodal tissue. The final results of 550 cases will be updated at the SABCS.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 1023.

Breast Cancer Initiating Cells Promote Chemoresistance by Pre-Activation of the DNA Damage Repair

Background: Breast tumor initiating cells (BT-ICs) display a variety of drug-resisting mechanisms including overxpression of ATP binding cassette (ABC) transporters and anti-apoptotic molecules. Unfortunately, application of P-glycoprotein inhibitors has not been successful in several clinical trials .Based on the tumor initiating cell concept, an alternative model posits that the T-ICs are naturally resistant to chemotherapy through their quiescence and their capacity for DNA repair. Gaining a better insight into the mechanisms of BT-IC resistance to chemotherapy might therefore lead to new therapeutic targets and better anticancer strategies.Material and Methods: We generated large numbers of BT-IC-enriched cells (SK-3rd) by in vivo passage of breast cancer cells SKBR3 in NOD/SCID mice treated with epirubicin, then enriched BT-ICs again by isolating spherical clusters of self-replicating cells (“mammospheres”) from suspension cultures. Under chemotherapy pressure, compared the apoptosis between BT-IC and non BT-IC by MTT, Annexin V, DNA ladder and hochest 33342 staining, and analyzed the cell cycles by Flow cytometry. We tested the DNA repair capacity after chemo-induced DNA damage between BT-IC and non BT-IC by single cell gel electrophoresis and tested the expression of DNA damage checkpoint protein by immunoblot.Results:SK-3rd formed 40-fold more mammospheres than SKBR3 (16.7%±2.6% vs 0.5%±0.2%; P&lt;0.001). Compared with non BT-IC, BT-IC treated with epirubicin showed more viability as assessed by MTT assay. After treated with 0.3ug/ml Epirubicin for 24 hours, withdrew the drug, and then repaired for 12, 24 hours respectively, analyzed the Annexin V positive cells in BT-IC were less than n non BT-IC(17.27%±2.3% vs 56%±6.7%; P=0.026), hochest staining also showed the similar results.SK-3rd mammospheric cells treated with or without Epirubicin arrested in G0/1 stage. Breast T-IC can repair chemo-induced DNA damage more efficiently than non BT-IC. Treated with or without Epirubicin, Sk-3rd mammospheric cells can pre-activated phosphorylated DNA chk2checkpoint (Thr68),but not in non BT-IC.Dicussion: The discovery of cancer initiating cells in solid tumors has changed our view of carcinogenesis and chemotherapy. In our study, we found that, BT-IC was more resistant than non BT-IC under the same chemotherapy pressure Although initiating cells can self-renew, they are generally quiescent, spending most of their time in G0. BT-IC treated with or without Epirubicin activated DNA checkpoint phosphorylated chk2 and arrested in G0/1 stage, which implied that BT-IC can target itself to arrest in G0/1 stage and pre-active chk2. When treated with DNA damage, BT-IC has enough time and quickly responses to repair damaged DNA, and at last contributes to the failure of chemotherapy. The new insight into the mechanisms of initiating -cell chemoresistance might allow the development of new strategies to improve targeted therapies in breast cancer.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 1121.

Water-dispersible carbon nanotubes for aqueous surface-initiated atom transfer radical polymerization

A simple one-pot process was developed for the covalent immobilization of atom transfer radical polymerization (ATRP) initiators with quaternized triethylamine moieties on the carboxyl-functionalized multiwalled carbon nanotubes (MWCNTs). The initiator-coupled MWCNTs exhibited good dispersion in water and could be used directly to prepare water-dispersion of polymer-MWCNT hybrids, such as stimuli-responsive poly(N-isopropyl acrylamide)-MWCNT hybrids, via surface-initiated ATRP of N-isopropylacrylamide in an aqueous medium. The present one-pot synthesis of the ATRP initiator-immobilized MWCNTs with good dispersion in water provides an alternative route to the direct preparation of water-soluble polymer-MWCNT hybrids in aqueous media.