Catherine Mitchell

Loss of CDKN2A expression is a frequent event in primary invasive melanoma and correlates with sensitivity to the CDK4/6 inhibitor PD0332991 in melanoma cell lines

We have investigated the potential for the p16‐cyclin D‐CDK4/6‐retinoblastoma protein pathway to be exploited as a therapeutic target in melanoma. In a cohort of 143 patients with primary invasive melanoma, we used fluorescence in situ hybridization to detect gene copy number variations (CNVs) in CDK4, CCND1, and CDKN2A and immunohistochemistry to determine protein expression. CNVs were common in melanoma, with gain of CDK4 or CCND1 in 37 and 18% of cases, respectively, and hemizygous or homozygous loss of CDKN2A in 56%. Three‐quarters of all patients demonstrated a CNV in at least one of the three genes. The combination of CCND1 gain with either a gain of CDK4 and/or loss of CDKN2A was associated with poorer melanoma‐specific survival. In 47 melanoma cell lines homozygous loss, methylation or mutation of CDKN2A gene or loss of protein (p16INK4A) predicted sensitivity to the CDK4/6 inhibitor PD0332991, while RB1 loss predicted resistance.

A signature predicting poor prognosis in gastric and ovarian cancer represents a coordinated macrophage and stromal response.

Purpose: Gene-expression profiling has revolutionized the way we think about cancer and confers the ability to observe the synchronous expression of thousands of genes. The use of putative genome-level expression profiles has allowed biologists to observe the complex interactions of genes that constitute recognized biologic pathways. We used gastric and ovarian datasets to identify gene-expression signatures and determine any functional significance. Experimental Design: Microarray data of 94-tumor and 45-benign samples derived from patients with gastric cancer were interrogated using Hierarchical Ordered Partitioning and Collapsing Hybrid analysis identifying clusters of coexpressed genes. Clusters were further characterized with respect to biologic significance, gene ontology, and ability to discriminate between normal and tumor tissue. Tumor tissues were separated into epithelial and stromal compartments and immunohistochemical analysis performed to further elucidate specific cell lineages expressing genes contained in the signature. Results: We identified a “stromal-response” expression signature, highly enriched for inflammatory, extracellular matrix, cytokine, and growth factor proteins. The majority of genes in the signature are expressed in the tumor-associated stroma but were absent in associated premalignant conditions. In gastric cancer, this module almost perfectly differentiates tumor from nonmalignant gastric tissue and hence can be regarded as a highly tumor-specific gene-expression signature. Conclusions: We show that these genes are consistently coexpressed across a range of independent gastric datasets as well as other cancer types suggesting a conserved functional role in cancer. In addition, we show that this signature can be a surrogate marker for M2 macrophage activity and has significant prognostic implications in gastric and ovarian high-grade serous cancer. Clin Cancer Res; 20(10); 2761–72. ©2014 AACR.

A phase Ib/II translational study of sunitinib with neoadjuvant radiotherapy in soft-tissue sarcoma.

Background:Preoperative radiotherapy (RT) is commonly used to treat localised soft-tissue sarcomas (STS). Hypoxia is an important determinant of radioresistance. Whether antiangiogenic therapy can ‘normalise’ tumour vasculature, thereby improving oxygenation, remains unknown.Methods:Two cohorts were prospectively enrolled. Cohort A evaluated the implications of hypoxia in STS, using the hypoxic tracer 18F-azomycin arabinoside (FAZA-PET). In cohort B, sunitinib was added to preoperative RT in a dose-finding phase 1b/2 design.Results:In cohort A, 13 out of 23 tumours were hypoxic (FAZA-PET), correlating with metabolic activity (r2=0.85; P<0.001). Two-year progression-free (PFS) and overall (OS) survival were 61% (95% CI: 0.44–0.84) and 87% (95% CI: 0.74–1.00), respectively. Hypoxia was associated with radioresistance (P=0.012), higher local recurrence (Hazard ratio (HR): 10.2; P=0.02), PFS (HR: 8.4; P=0.02), and OS (HR: 41.4; P<0.04). In Cohort B, seven patients received sunitinib at dose level (DL): 0 (50 mg per day for 2 weeks before RT; 25 mg per day during RT) and two patients received DL: −1 (37.5 mg per day for entire period). Dose-limiting toxicities were observed in 4 out of 7 patients at DL 0 and 2 out of 2 patients at DL −1, resulting in premature study closure. Although there was no difference in PFS or OS, patients receiving sunitinib had higher local failure (HR: 8.1; P=0.004).Conclusion:In STS, hypoxia is associated with adverse outcomes. The combination of sunitinib with preoperative RT resulted in unacceptable toxicities, and higher local relapse rates.

Loss of PML cooperates with mutant p53 to drive more aggressive cancers in a gender-dependent manner

p53 mutations and downregulation of promyelocytic leukemia (PML) are common genetic alterations in human cancers. In healthy cells these two key tumor suppressors exist in a positive regulatory loop, promoting cell death and cellular senescence. However, the influence of their interplay on tumorigenesis has not been explored directly in vivo. The contribution of PML to mutant p53 driven cancer was evaluated in a mouse model harboring a p53 mutation (p53wild-type/R172H) that recapitulates a frequent p53 mutation (p53R175H) in human sporadic and Li-Fraumeni cancers. These mice with PML displayed perturbation of the hematopoietic compartment, manifested either as lymphoma or extramedullary hematopoiesis (EMH). EMH was associated with peripheral blood leucocytosis and macrocytic anemia, suggestive of myeloproliferative- myelodysplastic overlap. In contrast, a complete loss of PML from these mice resulted in a marked alteration in tumor profile. While the incidence of lymphomas was unaltered, EMH was not detected and the majority of mice succumbed to sarcomas. Further, males lacking PML exhibited a high incidence of soft tissue sarcomas and reduced survival, while females largely developed osteosarcomas, without impact on survival. Together, these findings demonstrate that PML is an important tumor suppressor dictating disease development in a pertinent mouse model of human cancer. Key Points: (1) A mutant p53 allele disrupts hematopoiesis in mice, by promoting lymphomas and myeloproliferative / myelodysplastic overlap. (2) Coincidental p53 allele mutation and PML loss shifts the tumor profile toward sarcoma formation, which is paralleled in human leiomyosarcomas (indicated by immunohistochemistry; IHC).

Multiparametric 3T MRI in the evaluation of intraglandular prostate cancer: Correlation with histopathology

Prostate cancer is common and may be treated immediately or managed conservatively by observation. We sought to determine how reliable multiparametric MRI is in the detection of intraprostatic prostate cancer and what role it has in risk stratification.

Molecular changes in the phosphatidylinositide 3‐kinase (PI3K) pathway are common in gastric cancer

The phosphatidylinositide 3‐kinase (PI3K) pathway is an important signalling pathway that is frequently activated in cancer cells. This has led to the emergence of PI3K inhibitors as potential new treatment modalities for many cancers. We have investigated the frequency of molecular changes in the PI3K pathway in gastric cancer.

Cell density in prostate histopathology images as a measure of tumor distribution

We have developed an automatic technique to measure cell density in high resolution histopathology images of the prostate, allowing for quantification of differences between tumour and benign regions of tissue. Haemotoxylin and Eosin (H&E) stained histopathology slides from five patients were scanned at 20x magnification and annotated by an expert pathologist. Colour deconvolution and a radial symmetry transform were used to detect cell nuclei in the images, which were processed as a set of small tiles and combined to produce global maps of cell density. Kolmogorov-Smirnov tests showed a significant difference in cell density distribution between tumour and benign regions of tissue for all images analyzed (p < 0.05), suggesting that cell density may be a useful feature for segmenting tumour in un-annotated histopathology images. ROC curves quantified the potential utility of cell density measurements in terms of specificity and sensitivity and threshold values were investigated for their classification accuracy. Motivation for this work derives from a larger study in which we aim to correlate ground truth histopathology with in-vivo multiparametric MRI (mpMRI) to validate tumour location and tumour characteristics. Specifically, cell density maps will be registered with T2-weighted MRI and ADC maps from diffusion-weighted MRI. The validated mpMRI data will then be used to parameterise a radiobiological model for designing focal radiotherapy treatment plans for prostate cancer patients.

Clinical problem-solving. Spot diagnosis.

From the Victorian Clinical Genetics Service, Murdoch Childrens Research Institute (Z.S.), University of Melbourne (L.J.C., P.A.J., J.A.H., A.B., C.L., A.H.T.), and Children’s Cancer Centre, Royal Children’s Hospital (J.A.H.), Parkville; the Victorian Cancer Cytogenetics Service, St. Vincent’s Hospital, Fitzroy (L.J.C.); and the Departments of Pathology (C.M.) and Surgery (A.B., C.L.) and Familial Cancer Service (P.A.J., A.H.T.), Peter MacCallum Cancer Centre, East Melbourne — all in Victoria, Australia. Address reprint requests to Dr. Stark at the Victorian Clinical Genetics Service, 4th Fl., Murdoch Childrens Research Institute, Flemington Rd., Parkville VIC 3052, Australia, or at zornitza.stark@vcgs.org.au.

Molecular changes in the phosphatidylinositide 3-kinase (PI3K) pathway are common in gastric cancer

The phosphatidylinositide 3‐kinase (PI3K) pathway is an important signalling pathway that is frequently activated in cancer cells. This has led to the emergence of PI3K inhibitors as potential new treatment modalities for many cancers. We have investigated the frequency of molecular changes in the PI3K pathway in gastric cancer.

Updates of prostate cancer staging: Prostate-specific membrane antigen

The ability to accurately stage prostate cancer in both the primary and secondary staging setting can have a major impact on management. Until recently radiological staging has relied on computer tomography, magnetic resonance imaging, and nuclear bone scans to evaluate the extent of disease. However, the utility of these imaging technologies has been limited by their sensitivity and specificity especially in detecting early recurrence. Functional imaging using positron-emission tomography with a radiolabeled ligand targeted to prostate-specific membrane antigen has transformed the prostate cancer imaging landscape. Initial results suggest that it is a substantial improvement over conventional imaging in the setting of recurrence following primary therapy by having a superior ability to detect disease and to do so at an earlier stage. Additionally, it appears that the benefits seen in the secondary staging setting may also exist in the primary staging setting.