Early epigenetic downregulation of WNK2 kinase during pancreatic ductal adenocarcinoma development

Pancreatic ductal adenocarcinoma (PDAC) is usually incurable. Contrary to genetic mechanisms involved in PDAC pathogenesis, epigenetic alterations are ill defined. Here, we determine the contribution of epigenetically silenced genes to the development of PDAC. We analyzed enriched, highly methylated DNAs from PDACs, chronic pancreatitis (CP) and normal tissues using CpG island microarrays and identified WNK2 as a prominent candidate tumor suppressor gene being downregulated early in PDAC development. WNK2 was further investigated in tissue microarrays, methylation analysis of early pancreatic intraepithelial neoplasia (PanIN), mouse models for PDAC and pancreatitis, re-expression studies after demethylation, and cell growth assays using WNK2 overexpression. Demethylation assays confirmed the link between methylation and expression. WNK2 hypermethylation was higher in tumor than in surrounding inflamed tissues and was observed in PanIN lesions as well as in a PDAC mouse model. WNK2 mRNA and protein expressions were lower in PDAC and CP compared with normal tissues both in patients and mouse models. Overexpression of WNK2 led to reduced cell growth, and WNK2 expression in tissues correlated negatively with pERK1/2 expression, a downstream target of WNK2 responsible for cell proliferation. Downregulation of WNK2 by promoter hypermethylation occurs early in PDAC pathogenesis and may support tumor cell growth via the ERK-MAPK pathway.

P4-01-07: Combining Hedgehog Inhibitor, GDC-0449 with Tamoxifen Overcomes Tamoxifen-Resistance in In-Vitro and In-Vivo Studies of Estrogen-Receptor Positive Breast Cancer

Aims: Approximately 30–40% of patients with estrogen receptor positive (ER+) invasive breast cancer relapse despite targeted endocrine therapy with tamoxifen. Dependency of ER+ breast tumors shifts from estrogen to alternative cell survival mechanisms aberrantly activated over time facilitating drug-resistance and survival. We have identified Hedgehog (Hhg) signaling pathway as one such alternative pathway of survival activated in ER+ tumors that are resistant to tamoxifen. We sought to determine if treating such tumors with Hhg inhibitor and tamoxifen would improve outcomes.

Methods: Using MCF7 cell lines that are either sensitive (parental) or resistant to tamoxifen (4-hydroxy tamoxifen resistant-OHTR) and other ER+ cell lines, expression of Hhg markers (SHH, PTCH, SMO, GLI1, GLI2 and GLI3) and Hhg targets (SNAIL, MYC, BMI1 and FOXM1) was analyzed by Real-time RT-PCR, Western blotting and immunocytochemistry. GLI1 transactivation potential was measured using 8XGLI-Luciferase reporter plasmid. GLI1 was depleted in OHTR and T47D cells using GLI1siRNA. The GLI1 depleted cells were exposed to tamoxifen and assessed for i) cell viability by MTT assay, ii) extent of apoptosis by TUNEL assay and PARP/Caspase cleavage (Western blot), iii) cell cycle profile by flow cytometry and iv) presence of tumor initiating cells (TICs) by mammosphere formation assay. Effect of GDC-0449, a small molecule inhibitor of SMO was tested on OHTR cell induced xenografts in athymic nude mice by monitoring tumor growth and distant metastasis. Correlation of GLI1 expression in primary breast tumor tissues (assessed by immunohistochemistry) and disease-free interval was studied in women enrolled on an ongoing clinical trial (OSU 0483) in premenopausal women with ER+ breast cancer undergoing adjuvant oophorectomy and tamoxifen.

Results: Expression of Hhg signaling molecules and the targets are significantly activated in OHTR cells resistant to 0.5 and 1μM tamoxifen. Serial passage of the resistant cells in mice resulted in aggressive transformation of tumors that micro-metastasized to lung and liver. Concurrent increase in Hhg marker expression, TICs and acquisition of epithelial mesenchymal transition were observed in the cells derived from these tumors. Depletion of GLI1 in OHTR cells resulted in reduced proliferation, colony formation and mammosphere formation and increased apoptosis in presence of tamoxifen. Treatment of OHTR cells with GDC-0449 and tamoxifen inhibited cell proliferation in vitro and supressed tumor growth and distant metastasis of tamoxifen resistant xenografts in mice. Primary human breast tumors expressing higher level of GLI1 demonstrated a trend towards increased risk of recurrence (p= 0.08) after tamoxifen therapy.

Conclusions: Our work has demonstrated for the first time that activated Hhg signaling is an alternate survival mechanism for tamoxifen resistant breast cancer. Furthermore, targeting these tumors with a combination of tamoxifen and anti-Hhg therapy inhibited tumor growth and development of distant metastases demonstrating efficacy of this approach. Clinical trials using this combination in patients with advanced ER+ breast cancer are warranted and are under development.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P4-01-07.

Neural correlates of 'pessimistic' attitude in depression

BACKGROUND

Preparing for potentially threatening events in the future is essential for survival. Anticipating the future to be unpleasant is also a cognitive key feature of depression. We hypothesized that 'pessimism'-related emotion processing would characterize brain activity in major depression.MethodDuring functional magnetic resonance imaging, depressed patients and a healthy control group were cued to expect and then perceive pictures of known emotional valences--pleasant, unpleasant and neutral--and stimuli of unknown valence that could have been either pleasant or unpleasant. Brain activation associated with the 'unknown' expectation was compared with the 'known' expectation conditions.

RESULTS

While anticipating pictures of unknown valence, activation patterns in depressed patients within the medial and dorsolateral prefrontal areas, inferior frontal gyrus, insula and medial thalamus were similar to activations associated with expecting unpleasant pictures, but not with expecting positive pictures. The activity within a majority of these areas correlated with the depression scores. Differences between healthy and depressed persons were found particularly for medial and dorsolateral prefrontal and insular activations.

CONCLUSIONS

Brain activation in depression during expecting events of unknown emotional valence was comparable with activation while expecting certainly negative, but not positive events. This neurobiological finding is consistent with cognitive models supposing that depressed patients develop a 'pessimistic' attitude towards events with an unknown emotional meaning. Thereby, particularly the role of brain areas associated with the processing of cognitive and executive control and of the internal state is emphasized in contributing to major depression.

A case of late onset leukoencephalopathy with cerebral calcifications and cysts in a 59-year-old woman

BACKGROUND

Leukoencephalopathy with cerebral calcifications and cysts (LCC) is a recently described, very rare entity, clinically characterized by progressive neurological deficits such as cognitive decline, epileptic seizures, pyramidal, extrapyramidal and cerebellar symptoms/signs. With the exception of two patients with adult onset, in all previously described cases symptoms onset occurred between early infancy and adolescence.

RESULTS

We report a case of late onset LCC in a 59-year-old woman presenting with urinary and fecal incontinence and behavioural changes, then rapid progression with hemianopia, hemiparesis, ataxia and cognitive decline. Extensive work-up was performed, including brain magnetic resonance imaging, magnetic resonance spectroscopy, cyst fluid analysis and brain biopsy, confirming the final diagnosis of LCC.

CONCLUSION

Our case supports the existence of a late onset adult form of LCC.