Trastuzumab and vinorelbine in early stages of HER2-positive breast cancer

The combination of vinorelbine and trastuzumab (VH) is highly active and well tolerated in patients with metastatic HER2+ breast cancer. We assessed the efficacy and tolerability of VH as an alternative adjuvant treatment for patients with localized breast cancer refusing or ineligible for standard adjuvant trastuzumab-based chemotherapy. Twenty-eight patients with stage I-III breast cancer were treated only with VH as preoperative or postoperative chemotherapy. Fourteen patients received VH as adjuvant treatment for pT1a-b pN0 or eR+ pT1c pN0 cancers. VH was well tolerated, the only grade 3-4 toxicity being neutropenia with 2 cases of febrile neutropenia. At a median follow-up of 39 months, no breast cancer relapses were documented; moreover, overall and disease-free survival was 96.4%. In summary, our results indicate that VH is effective and well tolerated. VH should be prospectively tested as adjuvant treatment for pN0 pT1a-b breast cancer patients for which no standard treatment is well defined.

Magnetotactic bacteria penetration into multicellular tumor spheroids for targeted therapy

Preliminary experiments showed that MC-1 magnetotactic bacteria (MTB) could be used for the delivery of therapeutic agents to tumoral lesions. Each bacterium can provide a significant thrust propulsion force generated by two flagella bundles exceeding 4pN. Furthermore, a chain of single-domain magnetosomes embedded in the cell allows computer directional control and tracking using a magnetic resonance imaging (MRI) system. Although these embedded functionalities suggest that MTB when under the influence of an external computer could be considered as biological microrobots with the potential of targeting tumors, little is known about their level of penetration in tumoral tissues. In this paper, in vitro experiments were performed to assess the capability of these bacteria to penetrate tumor tissue for the delivery of therapeutic agents. Multicellular tumor spheroids were used since they reproduce many properties of solid tumors. The results show the ability of these MTB when submitted to a directional magnetic field to penetrate inside a 3D multicellular tumor spheroid through openings present in the tissue.

The effect of a DNA repair gene on cellular invasiveness: XRCC3 over-expression in breast cancer cells

Over-expression of DNA repair genes has been associated with resistance to radiation and DNA-damage induced by chemotherapeutic agents such as cisplatin. More recently, based on the analysis of genome expression profiling, it was proposed that over-expression of DNA repair genes enhances the invasive behaviour of tumour cells. In this study we present experimental evidence utilizing functional assays to test this hypothesis. We assessed the effect of the DNA repair proteins known as X-ray complementing protein 3 (XRCC3) and RAD51, to the invasive behavior of the MCF-7 luminal epithelial-like and BT20 basal-like triple negative human breast cancer cell lines. We report that stable or transient over-expression of XRCC3 but not RAD51 increased invasiveness in both cell lines in vitro. Moreover, XRCC3 over-expressing MCF-7 cells also showed a higher tumorigenesis in vivo and this phenotype was associated with increased activity of the metalloproteinase MMP-9 and the expression of known modulators of cell-cell adhesion and metastasis such as CD44, ID-1, DDR1 and TFF1. Our results suggest that in addition to its' role in facilitating repair of DNA damage, XRCC3 affects invasiveness of breast cancer cell lines and the expression of genes associated with cell adhesion and invasion.

Irinotecan and DNA-PKcs inhibitors synergize in killing of colon cancer cells

This study sought to measure the degree of synergy induced by specific small molecule inhibitors of DNA-PK [NU7026 and IC486241 (ICC)], a major component of the non-homologous end-joining (NHEJ) pathway, with SN38 or oxaliplatin. Synergy between the DNA damaging drugs and the DNA-PK inhibitors was assessed using the sulforhodamine-B assay (SRB). Effects of drug combinations on cell cycle and DNA-PK activity were determined using flow cytometry and western blot analysis. DNA damage was assessed via comet assay and quantification of γH2AX. The role of homologous recombination repair (HRR) was determined by nuclear Rad51 protein levels and a GFP reporter recombination assay. Significant reductions in the IC(50) values of SN38 were observed at 5 and 10 μM of DNA-PK inhibitors. Moreover, at 1-2 μM (attainable concentrations with ICC in mice) these DNA-PKcs inhibitors demonstrated synergistic reductions in the IC(50) of SN38. Flow cytometric data indicated that SN38 and SN38 in combination with DNA-PKcs inhibitors showed dramatic G2/M arrest at 24 h. Furthermore, reduced phosphorylation of DNA-PKcs and increased DNA damage were observed at this time point with SN38 in combination with DNA-PKcs inhibitors as compared to cells treated with SN38 alone. SN38 alone and in the presence of ICC increased nuclear Rad51 protein levels. Furthermore, inhibition of DNA-PKcs increased HRR suggesting that NHEJ is a negative regulator of HRR. These data indicate that small molecule inhibitors of DNA-PKcs dramatically enhance the efficacy of SN38 in colon cancer cell lines.

Vav-1 expression correlates with NFκB activation and CD40-mediated cell death in diffuse large B-cell lymphoma cell lines

Diffuse large B-cell lymphoma (DLBCL) is an aggressive malignancy with a variable response to therapy. We have previously shown that DLBCL cell lines differ in their susceptibility to CD40-mediated cell death, and that resistance to CD40-targeted antibodies correlated with increased expression of markers of immature B-cell and absence of Vav-1 mRNA. We used gene expression profiling to investigate the mechanism of CD40 resistance in these cell lines, and found that resistance correlated with lack of Vav-1 and inability to activate NFκB upon CD40 ligation. Analysis of tissue microarrays of 213 DLBCL cases revealed that Vav-1 expression correlated with a higher proliferative index and the presence of the post-germinal centre marker Irf-4. Our results suggest that Vav-1 expression may be associated with activated B-cell DLBCL origin and higher proliferative activity, and indicate Vav-1 as a potential marker to identify tumours likely to respond to CD40-targeted therapies.

p53 and autophagy contribute to dasatinib resistance in primary CLL lymphocytes

B-cell chronic lymphocytic leukemia (CLL) is the most common leukemia in adults and there is no cure for the disease. Although dasatinib is cytotoxic to primary CLL lymphocytes in vitro, the drug has been shown to be active in a small percent of CLL patients. Our previous results suggest that dasatinib targets del17 CLL lymphocytes which are the CLL patients with the worst prognosis. Here we present mechanistic evidence that dasatinib induces endoplasmic reticulum stress and autophagy in CLL lymphocytes. Furthermore we provide evidence suggesting that autophagy mediates resistance to the drugs, process that is modulated by p53.

Abstract LB-100: Optimal modulation of DNA repair in CLL therapy

Resistance to chlorambucil (CLB) in chronic lymphocytic leukemia (CLL) can occur as a consequence of increased DNA repair including c-abl stimulated Rad-51 related homologous recombinational repair (HRR) and DNA-PK related nonhomologous endjoining (NHEJ).

Recent reports suggest that the nonreceptor tyrosine kinase c-abl plays an important role in CLL. In particular, we have previously demonstrated that imatinib inhibition of c-abl or NU7026 inhibition of DNA-PK in CLL lymphocytes results in sensitization to CLB in most samples. Here we report that nilotinib, a superpotent (20-30 fold greater than niltinib) inhibitor of c-abl is more efficacious than imatinib in sensitizing CLL lymphocytes to CLB in the majority of the CLL lymphocyte samples associated with a greater nilotinib related inhibition of c-abl autophosporylation, increased apoptosis and decreased repair of CLB-induced DNA damage (increased activated H2AX).

Furthermore, in CLL samples in which c-abl was inhibited by either inhibitor, there was an increased activation of DNA-PK. Utilizing NU7026, a specific inhibitor of DNA-PK, with nilotinib or imatinib resulted in further sensitization to CLB but there was a greater sensitization to CLB with nilotinib than imatinib. These results suggest: (1) a more potent inhibition of c-abl is more efficacious in sensitizing CLL lymphocytes to CLB, (2) inhibition of c-abl results in a compensatory increase in DNA-PK and (3) inhibiting both DNA repair systems optimally sensitizes CLL lymphocytes to CLB, an effect which is most pronounced with the more potent c-abl inhibitor, nilotinib.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr LB-100.

Trastuzumab and vinorelbine (TV) in early stages of breast cancer

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Background: HER-2+ breast cancers (BCs) have a higher relapse rate, even for early stages of disease. The combination of trastuzumab and vinorelbine (TV) displays a high degree of synergism both preclinically and in metastatic BC patients that typically tolerate TV remarkably well. Occasionally, patients refuse standard treatment with chemotherapy and trastuzumab because of toxic side effects. In our institution, some of these patients accepted to receive treatment with TV. Methods: We retrospectively collected data on patients with stage I-III BCs, treated with TV as the only chemotherapy regimen. Most patients received TV on a weekly basis (one week off for V every 3–4 weeks) for ∼6 months, followed by 6 more months of T only. Results: Between May 2003 and June 2008, 23 patients were started on weekly TV. Median age was 66. Five patients received TV as preoperative treatment for BCs with the following clinical stages: IIB (1); IIIA (1); IIIB (3). The other 18 patients were pathologically staged as: stage I (11); IIA (5); IIIB (2). All cancers were HER2+; 65% of patients also received hormonal treatment for ER/PR+ disease. 3 patients had been previously treated for BC, and received TV as “adjuvant” treatment after a local relapse. Only one of these patients had previously received chemotherapy, while none had received prior T. No pathological complete response was found at surgery after preoperative TV. TV was very well tolerated, with one patient developing febrile neutropenia, 4 patients grade 3–4 uncomplicated neutropenia, and no other grade 3–4 events. During therapy, 5 patients had an asymptomatic 10–20% drop in the LVEF (Grade 1). Follow-up MUGA scans at 1 year after TV so far failed to show any significant abnormality. At an average follow-up of 26 months, one patient died for non-BC related causes, and all the other 22 patients are disease-free. Conclusions: TV is safe and very well tolerated, with no significant cardiac toxicity in our patient population. Preliminary follow-up data suggest that TV may be an acceptable alternative (neo-)adjuvant therapy for patients refusing “toxic” chemotherapy. Further studies prospectively testing TV as adjuvant treatment should be considered for patients with stage 1A BC, for which no standard treatment is clearly defined.

No significant financial relationships to disclose.

Dasatinib sensitizes primary chronic lymphocytic leukaemia lymphocytes to chlorambucil and fludarabine in vitro

The dual c-abl/Src kinase inhibitor, dasatinib, utilized to treat chronic myeloid leukaemia (CML) when used at clinically attainable sublethal concentrations, synergistically sensitized primary chronic lymphocytic leukaemia (CLL) lymphocytes to chlorambucil and fludarabine. In contrast, dasatinib alone demonstrated toxicity to CLL lymphocytes at concentrations that are generally not clinically attainable. Dasatinib resistance and poorer dasatinib-mediated sensitization to chlorambucil and fludarabine was associated with higher expression of c-abl protein levels. In contrast, chlorambucil and fludarabine resistance correlated with basal p53 protein levels. Moreover, Western blot analysis after in vitro treatment of primary CLL lymphocytes with dasatinib, chlorambucil and/or fludarabine, showed that dasatinib: (i) inhibited c-abl function (e.g. downregulation of c-abl protein levels and decreased the phosphorylation of a c-abl downstream target, Dok2), (ii) decreased chlorambucil/fludarabine induced accumulation of p53 protein levels, (iii) altered the response to chlorambucil/fludarabine induced DNA-damage as evidenced by an increase in chlorambucil/fludarabine-induced H2AX phosphorylation, and (iv) accentuated the c-abl downregulation induced by chlorambucil/fludarabine. Our results suggest that dasatinib in combination with chlorambucil or fludarabine may improve the therapy of CLL.

Identification and characterization of novel SNPs in CHEK2 in Ashkenazi Jewish men with prostate cancer

Checkpoint kinase 2 (CHEK2) is a protein involved in arresting cell cycle in response to DNA damage. To investigate whether it plays an important role in the development of prostate cancer (PRCA) in the Ashkenazi Jewish (AJ) population, we sequenced CHEK2 in 75 AJ individuals with prostate, breast, or no cancer (n=25 each). We identified seven coding SNPs (five are novel) that changed the amino-acid sequence, resulting in R3W, E394F, Y424H, S428F, D438Y, P509S, and P509L. We determined the frequency of each variant in 76 AJ families collected by members of the International Consortium for Prostate Cancer Genetics (ICPCG) where >or=2 men were affected by PRCA. Only one variant, Y424H in exon 11, was identified in more than two families. Exon 11 was then screened in nine additional AJ ICPCG families (a total of 85 families). The Y424H variant occurred in nine affected cases from four different families; however, it did not completely segregate with the disease. We performed bioinformatics analysis, which showed that Y424H is a non-conservative missense substitution that falls at a position that is invariant in vertebrate CHEK2 orthologs. Both SIFT and Align-GVGD predict that Y424H is a loss of function mutation. However, the frequency of Y424H was not significantly different between unselected AJ cases from Montreal/Memorial Sloan Kettering Cancer Centre (MSKCC) and AJ controls from Israel/MSKCC (OR 1.18, 95%CI: 0.34-4.61, p=.99). Moreover, functional assays using Saccharomyces cerevisiae revealed that the Y424H substitution did not alter function of CHEK2 protein. Although we cannot rule out a subtle influence of the CHEK2 variants on PRCA risk, these results suggest that germline CHEK2 mutations have a minor role in, if any, PRCA susceptibility in AJ men.

XRCC3 depletion induces spontaneous DNA breaks and p53-dependent cell death

In vertebrate cells, Xrcc3 initiates the repair of exogenous induced-DNA breaks during S and G(2)/M phases of the cell cycle by homologous recombination. However, much less is known of the role of Xrcc3 in the response to spontaneous DNA breaks. Using a siRNA approach, we show that depletion of XRCC3 inhibits the proliferation of MCF7 breast cancer cells. This inhibition of replication coincides with the accumulation of DNA breaks, as shown by the comet assay. Cell cycle specific analysis of gammaH2AX expression shows that S and G2/M phase cells express the highest fraction of gammaH2AX positive cells. This is consistent with replication-dependent accumulation of DNA breaks and deficient homologous recombination. While the induction of gammaH2AX is followed by cell death in parental cells, a p53 knockdown derivative becomes more resistant to XRCC3 depletion-induced death without changes in the levels of gammaH2AX. These results show that XRCC3 is required for the proliferation of MCF7 cells, and that decrease in its expression leads to the accumulation of DNA breaks and the induction of p53-dependent cell death.

Chlorambucil cytotoxicity in malignant B lymphocytes is synergistically increased by 2-(morpholin-4-yl)-benzo[h]chomen-4-one (NU7026)-mediated inhibition of DNA double-strand break repair via inhibition of DNA-dependent protein kinase

Chlorambucil (CLB) treatment is used in chronic lymphocytic leukemia (CLL) but resistance to CLB develops in association with accelerated repair of CLB-induced DNA damage. Phosphorylated histone H2AX (gammaH2AX) is located at DNA double-strand break (DSB) sites; furthermore, it recruits and retains damage-responsive proteins. This damage can be repaired by nonhomologous DNA end-joining (NHEJ) and/or homologous recombinational repair (HR) pathways. A key component of NHEJ is the DNA-dependent protein kinase (DNA-PK) complex. Increased DNA-PK activity is associated with resistance to CLB in CLL. We used the specific DNA-PK inhibitor 2-(morpholin-4-yl)-benzo[h]chomen-4-one (NU7026) to sensitize CLL cells to chlorambucil. Our results indicate that in a CLL cell line (I83) and in primary CLL-lymphocytes, chlorambucil plus NU7026 has synergistic cytotoxic activity at nontoxic doses of NU7026. CLB treatment results in G(2)/M phase arrest, and NU7026 increases this CLB-induced G(2)/M arrest. Moreover, a kinetic time course demonstrates that CLB-induced DNA-PK activity was inhibited by NU7026, providing direct evidence of the ability of NU7026 to inhibit DNA-PK function. DSBs, visualized as gammaH2AX, were enhanced 24 to 48 h after CLB and further increased by CLB plus NU7026, suggesting that the synergy of the combination is mediated by NU7026 inhibition of DNA-PK with subsequent inhibition of DSB repair.