Carbon monoxide mediates the anti-apoptotic effects of heme oxygenase-1 in medulloblastoma DAOY cells via K+ channel inhibition

Tumor cell survival and proliferation is attributable in part to suppression of apoptotic pathways, yet the mechanisms by which cancer cells resist apoptosis are not fully understood. Many cancer cells constitutively express heme oxygenase-1 (HO-1), which catabolizes heme to generate biliverdin, Fe(2+), and carbon monoxide (CO). These breakdown products may play a role in the ability of cancer cells to suppress apoptotic signals. K(+) channels also play a crucial role in apoptosis, permitting K(+) efflux which is required to initiate caspase activation. Here, we demonstrate that HO-1 is constitutively expressed in human medulloblastoma tissue, and can be induced in the medulloblastoma cell line DAOY either chemically or by hypoxia. Induction of HO-1 markedly increases the resistance of DAOY cells to oxidant-induced apoptosis. This effect was mimicked by exogenous application of the heme degradation product CO. Furthermore we demonstrate the presence of the pro-apoptotic K(+) channel, Kv2.1, in both human medulloblastoma tissue and DAOY cells. CO inhibited the voltage-gated K(+) currents in DAOY cells, and largely reversed the oxidant-induced increase in K(+) channel activity. p38 MAPK inhibition prevented the oxidant-induced increase of K(+) channel activity in DAOY cells, and enhanced their resistance to apoptosis. Our findings suggest that CO-mediated inhibition of K(+) channels represents an important mechanism by which HO-1 can increase the resistance to apoptosis of medulloblastoma cells, and support the idea that HO-1 inhibition may enhance the effectiveness of current chemo- and radiotherapies.

The conjugation of an AQP1-directed immunotoxin in the study of site-directed therapy within the CNS

PURPOSE

The water channel, aquaporin (AQP)1, is highly specific to the choroid plexus (CP) epithelium within the brain. It is therefore a potential target through which therapeutic agents could be selectively directed to the CP. Here we describe the conjugation of a monoclonal antibody (mAb), raised against an extra-cellular domain of AQP1, to the A chain of ricin (RCA). This reagent should allow study of a highly specific chemical lesion of the CP.

METHODS

A published method was used to couple the anti-AQP1 mAb to the A chain of ricin using an SPDP cross-linker. The conjugate was purified by Superdex S-200 chromatography. Column fractions were analysed by SDS-PAGE and Western blotting. Fractions containing conjugate were assayed for cytotoxicity on rat CP cells in culture, using a WST-1 viability assay to assess cell death.

RESULTS

SDS-PAGE and Western blotting demonstrated separation of conjugated anti-AQP1 mAb from unconjugated ricin by the Superdex column. Cultured rat CP cells were killed with an IC(50) of 1.81 μg/ml when exposed to the anti-AQP1 mAb-RCA conjugation reaction products. Selectivity of this reagent was demonstrated by the higher IC(50) exhibited by non-AQP1-expressing primary fibroblast cultures and cultures exposed to the reaction products from the non-specific IgG-RCA conjugation attempt.

CONCLUSION

We have been able to demonstrate selective cytotoxicity in vitro of an anti-AQP1 mAb-RCA conjugate. We hope that this work will generate further interest in the use of this site-specific conjugate to target the CP in conditions such as hydrocephalus, tumours that arise from here, and other AQP1-expressing tumours.

H1047R phosphatidylinositol 3-kinase mutant enhances HER2-mediated transformation by heregulin production and activation of HER3

Hyperactivation of phosphatidylinositol-3 kinase (PI3K) can occur as a result of somatic mutations in PIK3CA, the gene encoding the p110α subunit of PI3K. The HER2 oncogene is amplified in 25% of all breast cancers and some of these tumors also harbor PIK3CA mutations. We examined mechanisms by which mutant PI3K can enhance transformation and confer resistance to HER2-directed therapies. We introduced the PI3K mutations E545K and H1047R in MCF10A human mammary epithelial cells that also overexpress HER2. Both mutants conferred a gain of function to MCF10A/HER2 cells. Expression of H1047R PI3K but not E545K PI3K markedly upregulated the HER3/HER4 ligand heregulin (HRG). HRG siRNA inhibited growth of H1047R but not E545K-expressing cells and synergized with the HER2 inhibitors trastuzumab and lapatinib. The PI3K inhibitor BEZ235 markedly inhibited HRG and pAKT levels and, in combination with lapatinib, completely inhibited growth of cells expressing H1047R PI3K. These observations suggest that PI3K mutants enhance HER2-mediated transformation by amplifying the ligand-induced signaling output of the ErbB network. This also counteracts the full effect of therapeutic inhibitors of HER2. These data also suggest that mammary tumors that contain both HER2 gene amplification and PIK3CA mutations should be treated with a combination of HER2 and PI3K inhibitors.

Distribution of uranium in drinking water and associated age-dependent radiation dose in India

Exposure due to natural radiation is of particular importance because it accounts for the largest contribution (nearly 85 %) to the total collective dose of the world population. An attempt has been made to present the feasibility of uranium occurrence in drinking water samples from different states of India, by laser-induced fluorimetry. The associated age-dependent radiation dose was estimated by taking the prescribed water intake values of different age groups. The concentration of uranium obtained, i.e. 0.1 +/- 0.01 to 19.6 +/- 1.8 microg l(-1), is well below the drinking water guideline value of 30 microg l(-1). The annual ingestion dose due to uranium in drinking water for various age groups is found to vary from 0.14 to 48 microSv y(-1).

MIB1 proliferation index in meningiomas: does it predict recurrence? A clinicopathological study

The usefulness of proliferation marker MIB1 in predicting recurrences in cranial meningiomas when other clinical and pathological factors are considered was assessed. Data from 65 patients with meningiomas were analysed and their clinical notes reviewed to define the Simpson grade of surgical excision, the location of tumour, amongst other clinical factors. The diagnosis was reviewed; immunohistochemical staining for a proliferation marker MIB1 was carried out on archival formalin-fixed, paraffin-embedded tumour and a labelling index for MIB1 (MIB1 L1) calculated. Analysis was undertaken of the impact of histology, grade of excision, tumour location and proliferation index on the risk of recurrence. The grade of surgical resection and histology type were the most important factors likely to predict recurrence. MIB1 LI was not considered useful in predicting tumour recurrence.

Intradural extramedullary primary malignant melanoma radiographically mimicking a neurofibroma

A case of intradural extramedullary primary malignant melanoma mimicking the presentation of a neurofibroma is described. We emphasise the fact that surgeons should be aware of unexpected malignant lesions involving spinal nerve roots.

A rare case of recurrent secretory meningioma with malignant transformation

A 72-year-old woman previously operated for a sphenoid-ridge meningioma, now presented with double vision. Histology showed a secretory meningioma with an epithelial-appearing, malignant component. Malignant transformation in a secretory meningioma is not known. This is the first report of such an occurrence.

Exon 9 and exon 20 mutations in PIK3CA confer resistance to HER2 inhibitors in HER2-overexpressing breast cancer cells

Abstract #4054

The anti-tumor effect of HER2 antagonists in HER2-dependent breast cancer cells has been proposed to rely on inhibition of the phosphatidylinositol-3 kinase (PI3K)/Akt pathway. Mutations in the p110α catalytic subunit of PI3K occur in up to 40% of breast cancers and activation of this pathway has been implicated in resistance to the HER2 antibody trastuzumab (T). PIK3CA mutations cluster in two regions in the helical (E542K, E545K; exon 9) and catalytic (H1047R; exon 20) domains. We studied the role of these mutants in resistance to HER2 inhibitors in breast cancer cells with HER2 amplification. Two lines with endogenous H1047R p110 (PI3K), SUM190 and HCC1954, and SKBR3, SUM225, and BT474 cells stably transduced with retroviral vectors encoding HA-tagged wild-type, E545K, or H1047R p110, were studied for their response to the HER2 tyrosine kinase inhibitor lapatinib ditosylate (L; GW-572016) and T. In monolayer and 3D cell proliferation assays, partial resistance to L and T was conferred by either mutation compared to WT p110. After prolonged L treatment, Ser473 phosphorylation of Akt recovered in all cells with endogenous or ectopic p110 mutants in spite of continued inhibition of Y1248 P-HER2 and Y1289 P-HER3 by L. Further, BT474 cells with either p110 mutant could be passaged in the continued presence of L. Immunoprecipitation of p85, the regulatory subunit of PI3K, showed that PI3K association with HER3 was abrogated by T and L. RNAi of HER3 in MCF10A/HER2/PI3KE545K and MCF10A/HER2/PI3KH1047R cells markedly but not completely inhibited growth suggesting that the PI3K mutants may still depend on HER3 for full activation. We hypothesized that in cells with mutant PI3K, the mutants coexist in a pool with WT enzyme, and that mutant and WT p110α are bound to p85 in variable proportions. Experiments to measure whether the ratio of mutant to WT p110 bound to p85, assayed by mass spectrometry, will increase in the PI3K-mutant cells with acquired resistance to L are in progress. To test the role of these mutants on resistance to anti-HER2 therapies in vivo, athymic mice bearing BT474 xenografts with ectopic WT, E545K, or H1047R p110 are undergoing treatment with L and T. Finally, we analyzed mutations of PIK3CA in a cohort of 40 patients with locally advanced HER2+ breast cancer treated with weekly single-agent T for 3 weeks, followed by T with docetaxel for a total of 12 weeks before surgery (Mohsin et al. JCO 23:2460, 2005). Sequential core biopsies at weeks 1 and 3 after initiation of T were taken. Eight of 40 tumors (20%) expressed mutant PI3K, 2 in exon 9 and 6 in exon 20. PIK3CA mutations did not correlate with change in Ki67 (p=0.97) or cleaved caspase 3 (p=0.51) in weeks 1 or 3 of treatment nor with pathologic complete response (p=0.21). These data suggest that, if mutant PI3K confers relative resistance to T, a shorter time to recurrence may be a more robust endpoint as the initial cellular or clinical response may not be a good indicator of this resistance.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 4054.

Renal cell carcinoma in allograft kidney - a case report with unusual findings at autopsy

A 30-year old male who had a non-related cadaveric renal transplant at the age of 12 years, presented with generalised CNS symptoms and meningeal enhancement on CT scan of the brain, 18 years after the transplantation. Autopsy revealed renal cell carcinoma in the transplanted kidney and metastatic tumour in a variety of organs including the brain. Prior ultrasound scans done at various post-transplant periods had all been normal.

Deferiprone, an orally deliverable iron chelator, ameliorates experimental autoimmune encephalomyelitis

The iron chelator, Desferal, suppressed disease activity of experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis (MS), and it has been tested in pilot trials for MS. The administration regimen of Desferal is cumbersome and prone to complications. Orally-deliverable, iron chelators have been developed that circumvent these difficulties, and the objective of this study was to test an oral chelator in EAE. SJL mice with active EAE were randomly assigned to receive deferiprone (150 mg/kg) or vehicle (water) 2×/day via gavage. EAE mice given deferiprone had significantly less disease activity and lower levels of inflammatory cell infiltrates (revealed by H&E staining) than EAE mice administered vehicle. T-cell infiltration, assessed by anti-CD3 immunohistochemical staining, also was reduced, although not significantly. Splenocytes cultured from naïve SJL mice were stimulated with anti-CD3 and anti-CD28 with or without 250 μM deferiprone. While ~39% of costimulated splenocytes without deferiprone underwent division, only ~2.8% of costimulated splenocytes with deferiprone divided and the latter cells were only 53% as viable as the former. Deferiprone had no effect on proliferation or viability of cells that were not costimulated. In summary, deferiprone effectively suppressed active EAE disease and it inhibited T-cell function. Multiple Sclerosis 2007; 13: 1118—1126. http://msj.sagepub.com

High grade glioma in a focal cortical dysplastic lesion

A 61-year-old woman presented in 1999 with a recent onset of left-sided focal clonic seizures with associated vague speech arrests. A computerised tomography (CT) scan revealed a hypoattenuated non-enhancing lesion within her right temporal lobe which was biopsied and the histopathological features were reported to be consistent with a hamartoma, reminiscent of tuberous sclerosis. Her seizures remained partially controlled with phenytoin and carbamazepine. She presented again 2 years later with an increase in the frequency of her seizures. A magnetic resonance scan of her brain demonstrated a homogenously enhancing mass lesion in her right temporo-parietal lobe. An initial lobectomy showed a hamartomatous lesion on histology but a subsequent sample obtained from a wide resection carried out when there was further worsening of her condition revealed a grade IV astrocytoma within a focal cortical dysplastic lesion. Our case highlights the importance of considering the possibility of a cortical dysplastic lesion harbouring a malignancy and the need for further research to explore the behaviour of these malformative lesions.

Cervical spine metastasis from adrenal pheochromocytoma

Metastatic tumours are the most common type of tumours in the spine of which only 10% occur in the cervical spine. We report a rare presentation of metastatic pheochromocytoma of the cervical spine which was successfully treated operatively. Adequate precautions should be taken during surgery as the tumour is very vascular. Radiotherapy is useful in the treatment of residual tumour.

Gorham's disease of skull base and cervical spine--confusing picture in a two year old

The unusual presentation of Gorham's disease of skull base and cervical spine in a two-year-old female child with radiological signs mimicking those of raised intracranial pressure is discussed. The differential diagnosis consists of skull base tumours, meningitis, osteomyelitis of the base of skull, congenital hydrocephalaus and congenital syndromes involving the skull base. Pathologically it can be very difficult to differentiate it from lymphangioma of the bone. Difficulty in establishing the diagnosis is discussed along with failure of radiotherapy and palmidronate therapy to cause arrest of the disease process and failure of surgery to provide stabilisation. We describe the course of the disease in this child over the period of last eight years. To the best of our knowledge this is the youngest case of Gorham's described so far.

Intracranial non-Hodgkin's MALT lymphoma mimicking a large convexity meningioma

Primary presentation of an intradural Non-Hodgkin's lymphoma is rare. Recently these B cell lymphomas of mucosa associated lymphoid tissue (MALT) have gained acceptance as an important pathological subtype and are distinguishable from other primary CNS lymphomas that exhibit aggressive behaviour. Over the past decade a number of these lesions have been reported to resemble a meningioma both intra-operatively and radiologically. The authors outline such a case of marginal zone B cell lymphoma that clinically and radiologically resembled a meningioma. This case illustrates the rare occurrence of low grade dural B cell lymphoma and the need to consider this entity in the differential diagnosis of CNS lesions, if appropriate targeted therapy is to be administered.

Management of Vascular Injuries in a Forward Hospital

BACKGROUND

Management of vascular injuries poses a challenging problem under warlike conditions. Several authorities recommend limb revascularisation only within first 6-8 hours, as the outcome after delayed revascularisation is poor.

METHODS

A retrospective analysis of 61 consecutive patients with vascular injury in a forward hospital over a 25- month period was carried out.

RESULTS

Vascular injuries constituted 3.1% of all injuries. The mean injury to treatment delay (lag time) was 11 hours, and 10 patients received treatment after 12 hours. The overall amputation rate was 15%, but only 6.5% for those revascularised within 12 hours and 44% for those undergoing surgery after 12 hours (Chi-square 4.59, p < 0.05). Presence of associated fractures was associated with an adverse outcome (Chi-square 4.24, p < 0.05), as was ligation in comparison to revascularisation (Chi-square 7.86, p < 0.005). Popliteal injuries were associated with a high amputation rate.

CONCLUSIONS

Failure to revascularise (ligation of artery), presence of associated fracture, and restoration of circulation beyond 12 hours are associated with a high amputation rate.