Nuclear PTEN controls DNA repair and sensitivity to genotoxic stress

Loss of function of the phosphatase and tensin homolog deleted on chromosome 10 (PTEN) tumor suppressor gene is associated with many human cancers. In the cytoplasm, PTEN antagonizes the phosphatidylinositol 3-kinase (PI3K) signaling pathway. PTEN also accumulates in the nucleus, where its function remains poorly understood. We demonstrate that SUMOylation (SUMO, small ubiquitin-like modifier) of PTEN controls its nuclear localization. In cells exposed to genotoxic stress, SUMO-PTEN was rapidly excluded from the nucleus dependent on the protein kinase ataxia telangiectasia mutated (ATM). Cells lacking nuclear PTEN were hypersensitive to DNA damage, whereas PTEN-deficient cells were susceptible to killing by a combination of genotoxic stress and a small-molecule PI3K inhibitor both in vitro and in vivo. Our findings may have implications for individualized therapy for patients with PTEN-deficient tumors.

Nuclear PTEN controls DNA repair and sensitivity to genotoxic stress

Loss of function of the phosphatase and tensin homolog deleted on chromosome 10 (PTEN) tumor suppressor gene is associated with many human cancers. In the cytoplasm, PTEN antagonizes the phosphatidylinositol 3-kinase (PI3K) signaling pathway. PTEN also accumulates in the nucleus, where its function remains poorly understood. We demonstrate that SUMOylation (SUMO, small ubiquitin-like modifier) of PTEN controls its nuclear localization. In cells exposed to genotoxic stress, SUMO-PTEN was rapidly excluded from the nucleus dependent on the protein kinase ataxia telangiectasia mutated (ATM). Cells lacking nuclear PTEN were hypersensitive to DNA damage, whereas PTEN-deficient cells were susceptible to killing by a combination of genotoxic stress and a small-molecule PI3K inhibitor both in vitro and in vivo. Our findings may have implications for individualized therapy for patients with PTEN-deficient tumors.

Occupational exposure to raw meat: a newly-recognized risk factor for Staphylococcus aureus nasal colonization amongst food handlers

Staphylococcus aureus contaminating raw meat may increase nasal colonization risk for occupationally-exposed food handlers. Food handlers from six catering establishments were nasally sampled for S. aureus and completed a questionnaire on carriage risk factors. Isolates were characterized for antibiotic susceptibility, spa type and, for methicillin-resistant strains, SCCmec type. Of 434 food handlers, 99 (22.8%) were colonized with S. aureus. Five isolates were methicillin-resistant belonging to SCCmec IV (2) and V (3). Resistance to tetracycline (20%), and erythromycin (16%) was high, but <10% to other antibiotics. Spa typing revealed 17% of isolates as t189, with 8% each t127 and t1081. Food handlers ever handling raw meat had a significantly higher colonization risk (OR=2.7; 95% CI: 1.7-4.5), increasing to 3.7 (95% CI: 2.0-6.8) for those always exposed. This is the first report of increased colonization risk in food handlers exposed to raw meat. This occupational hazard may increase infection risk, so improved compliance with workplace hygiene may be required.

Colonization of butchers with livestock-associated methicillin-resistant Staphylococcus aureus

Reports have documented colonization of swine in Europe, North America and more recently in China with livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA). Contamination of pig farmers, veterinarians and abattoir workers with these strains has been observed. However, although contamination levels of 10% of retail pork were reported from the Netherlands and Canada, there are limited data of contamination rates of workers handling raw meat. We investigated the rates of MRSA contamination of local butchers working in wet markets, where recently slaughtered pigs are cut up. Nasal swabs collected from 300 pork butchers at markets throughout Hong Kong were enriched in brain heart infusion broth with 5% salt and cultured on MRSASelect(®) . Isolates were confirmed as Staphylococcus aureus and susceptibility testing performed. The presence of mecA was confirmed, SCCmec and spa type determined and relatedness investigated by PFGE. Subjects completed a questionnaire on MRSA carriage risk factors. Seventeen samples (5.6%) yielded MRSA, 15 harbouring SCCmec IVb. Ten strains were t899 (CC9), previously reported from local pig carcasses. Five strains were healthcare associated: SCCmec type II, t701(CC6), colonizing two subjects at the same establishment, and single isolates of t008 (CC8), t002 (CC5) and t123 (CC45). The remaining isolates were t359 (CC97), previously reported from buffaloes, and t375 (CC5), reported from bovine milk. None of these butchers reported recent hospitalization or a healthcare worker in the family. Two had recently received antibiotics, one for a skin infection. Four reported wound infections within the last year. All were exposed to meat for >9 h per day. Carriage of MRSA was higher in butchers than in the general community. Although five strains were probably of healthcare origin, the high incidence of t899 (CC9) suggests that cross-contamination from pork occurs frequently. Washing of hands after touching raw pork is advised.

Preparation of mouse-human chimeric antibody against pancreatic cancer-associated mucin

A murine monoclonal antibody, designated Nd2, was generated using a purified mucin from the human pancreatic cancer cell line SW1990 as the immunogen. Administration of Nd2 into the patients with pancreatic cancer has shown that Nd2 is of clinical use for in vivo diagnostics of pancreatic cancer. In this study, starting with a previously established hybridoma producing Nd2, we have established a transfected cell line expressing a recombinant chimeric Nd2 composed of mouse-derived antigen-binding variable regions and human-derived constant regions. The chimeric Nd2 was shown to bind purified mucin from SW1990 cells with the same dose-response curve as the original Nd2. Immunohistochemical experiments have shown that the reactivity of the chimeric Nd2 in normal and malignant pancreatic tissue is also the same as that of the original Nd2. Replacement of a substantial portion of the mouse protein makes this chimeric Nd2 more promising for clinical application than the original mouse-derived Nd2 because its antigenicity is expected to be reduced.

New radioimmunoassay for pancreatic cancer-associated antigen span-1 with reference to differential-diagnosis and monitoring in pancreatic-cancer

Sera from patients with various malignant benign disorders, as well as from a large number of healthy blood donors (2197). were analyzed with a newly developed SPan-1 coated bead radioimmunoassay. Only 0.9% of the healthy patients had SPan-1 levels above the cut-off value. SPan-1 antigen levels were elevated in 89.2% of sera from pancreatic cancer patients and in 75% of T1 and T2 cancers. High diagnostic accuracy was also recognized in differentiating benign pancreatic diseases from pancreatic cancers. SPan-I levels decreased after pancreatic resection and rose again at recurrence of disease. SPan-1 could be distinguished from other tumor markers such as DU-PAN-2 and OC-125 by competition radioimmunoassays and was elevated in individuals with malignant gastrointestinal diseases who had normal levels of either or both CEA and CA 19-9 antigens. This rapid. reproducible and sensitive assay for SPan-I appears to be a useful procedure for the detection and follow-up of pancreatic cancer.

Immune reconstitution inflammatory syndrome associated with disseminated Mycobacterium sherrisii infection

Mycobacterium sherrisii is a recently described mycobacterium closely related to Mycobacterium simiae. There have been only a few reports of this organism causing disease, predominantly in the setting of HIV with severe immunosuppression. We report the first case of disseminated M. sherrisii associated with immune reconstitution inflammatory syndrome.

Detection of clinical and subclinical tubulo-interstitial inflammation by the urinary CXCL10 chemokine in a real-life setting

Urinary CXCL10 is a promising noninvasive biomarker for tubulo-interstitial allograft inflammation, but its diagnostic characteristics have not been assessed in a real-life setting. We investigated urinary CXCL10 in 213 consecutive renal allograft recipients having 362 surveillance biopsies at 3/6 months and 80 indication biopsies within the first year posttransplant. Allograft histology results were classified as (i) acute Banff score zero, (ii) interstitial infiltrates only, (iii) tubulitis t1, (iv) tubulitis t2-3 and (v) isolated vascular compartment inflammation. For clinical and subclinical pathologies, urinary CXCL10 correlated well with the extent of tubulo-interstitial inflammation. To determine diagnostic characteristics of urinary CXCL10, histological groups were separated into two categories: no relevant inflammation (i.e. acute Banff score zero and interstitial infiltrates only) versus all other pathologies (i.e. tubulitis t1-3 and isolated vascular compartment inflammation). For subclinical pathologies, AUC was 0.69 (sensitivity 61%, specificity 72%); for clinical pathologies, AUC was 0.74 (sensitivity 63%, specificity 80%). A urinary CXCL10-guided biopsy strategy would have reduced performance of surveillance and indication biopsies by 61% and 64%, respectively. Missed (sub)clinical pathologies were mostly tubulitis t1 and isolated vascular compartment lesions. In real life, urinary CXCL10 had clinically useful diagnostic properties making it a candidate biomarker to guide allograft biopsies.

Evolution and clinical pathologic correlations of de novo donor-specific HLA antibody post kidney transplant

The natural history for patients with de novo donor-specific antibodies (dnDSA) and the risk factors for its development have not been well defined. Furthermore, clinical and histologic correlation with serologic data is limited. We studied 315 consecutive renal transplants without pretransplant DSA, with a mean follow-up of 6.2 ± 2.9 years. Protocol (n = 215) and for cause (n = 163) biopsies were analyzed. Solid phase assays were used to screen for dnDSA posttransplant. A total of 47 out of 315 (15%) patients developed dnDSA at a mean of 4.6 ± 3.0 years posttransplant. Independent predictors of dnDSA were HLA-DRβ1 MM > 0 (OR 5.66, p < 0.006); and nonadherence (OR 8.75, p < 0.001); with a strong trend toward clinical rejection episodes preceding dnDSA (OR 1.57 per rejection episode, p = 0.061). The median 10-year graft survival for those with dnDSA was lower than the No dnDSA group (57% vs. 96%, p < 0.0001). Pathology consistent with antibody-mediated injury can occur and progress in patients with dnDSA in the absence of graft dysfunction and furthermore, nonadherence and cellular rejection contribute to dnDSA development and progression to graft loss.

P1-12-25: Evaluation of PTEN, EGFR and Ki67 Expression as Predictors of Response to a Trastuzumab-Containing Neoadjuvant Chemotherapy Regimen in a HER-2 Over-Expressing Locally Advanced Breast Cancer (LABC) Trial

Background: In patients with HER-2 over-expressing breast cancer, predictors of trastuzumab response and resistance remain unclear and unvalidated. In an exploratory analysis within a phase II trial, we evaluated various biologic markers as predictors of response or resistance to a trastuzumab containing neoadjuvant chemotherapy regimen.

Methods: A tissue microarray (TMA) was constructed from formalin-fixed paraffin-embedded tumor tissue samples obtained prior to neoadjuvant chemotherapy in 21 (from a total of 30) HER-2 positive stage II-III patients. Protocol treatment consisted of 4 cycles of 5-Fluorouracil, Epirubicin and Cyclophosphamide (FEC100) followed by 4 cycles of Docetaxel, Carboplatin (AUC 6) and Trastuzumab (TCH). Immunohistochemical (IHC) analyses of estrogen receptor (ER), progesterone receptor (PR), HER-2, Ki67, EGFR and PTEN were performed utilizing previously published protocols and cut-offs. HER-2 equivocal (2+) by IHC cases was confirmed by prior FISH analysis. Fisher's exact test was used for statistical analysis.

Results: 21 patients had sufficient tumour for analysis. Median age at diagnosis was 49 years old, 67% were pre-menopausal, and biomarker expression was as follows: 43% ER positive, 29% PR positive, and 100% HER-2 positive. 14 patients (67%) had pathologic complete response (pCR) following the completion of neoadjuvant chemotherapy and trastuzumab. In general, tumour samples showed high Ki67 (&gt;14%) staining (62%), low EGFR positivity (14%), and high PTEN expression (71%). Neither high Ki67 expression (p=0.65), any EGFR expression (p=0.26), nor PTEN loss (p=0.60) was associated with higher or lower rates of pCR respectively.

Conclusion: In our small cohort of locally advanced HER-2 over-expressing tumours, baseline expression of Ki67, EGFR and PTEN were not associated with pCR to a neoadjuvant sequential anthracycline and taxane/trastuzumab combination regimen. Additional biomarkers for an activated PI3K pathway and for p95 will be attempted.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P1-12-25.