Improving precise counting of mitotic cells in mantle cell lymphoma using phosphohistone H3 (PHH3) antibody.

AIMS: Mantle cell lymphoma (MCL) has a highly heterogeneous clinical course ranging from indolent, to aggressive and rapidly progressive disease. Proliferation is a strong predictor for disease outcome. In routine clinical practice, Ki-67 expression is used as a measure of proliferation. However, several studies have documented a high degree of inter-laboratory and inter-observer variation with Ki-67 immunohistochemistry. Phosphorylation of histone H3 occurs specifically during mitosis and hence serves as a specific marker for cells in mitosis. METHODS AND RESULTS: We investigated phosphohistone H3 (PHH3) immunohistochemistry as a proliferation maker in 28 tissue biopsies of MCL and compared the PHH3 results (as evaluated by direct microscopic visualisation and image analysis-aided scoring) with morphological subtyping, mitotic counts and Ki-67 index. We found PHH3-mitotic count was about sixfold higher than H&E-mitotic count (mitoses in 10 high power fields). Furthermore, PHH3-mitotic count in aggressive morphological variants of MCL was significantly higher than in usual MCL. The PHH3-mitotic count showed a strong linear correlation with PHH3-mitotic index (percentage positive cells). CONCLUSIONS: We found PHH3 immunohistochemistry, a reliable mitosis-specific marker, in MCL. Performing precise counts and evaluating precise proliferation indices is easier with PHH3 immunohistochemistry. This contrasts with the conventional estimation of Ki-67 percentages by 'eye-balling'.

Phase I study of GSK461364, a specific and competitive Polo-like kinase 1 inhibitor, in patients with advanced solid malignancies.

PURPOSE: GSK461364 is an ATP-competitive inhibitor of polo-like kinase 1 (Plk1). A phase I study of two schedules of intravenous GSK461364 was conducted. EXPERIMENTAL DESIGN: GSK461364 was administered in escalating doses to patients with solid malignancies by two schedules, either on days 1, 8, and 15 of 28-day cycles (schedule A) or on days 1, 2, 8, 9, 15, and 16 of 28-day cycles (schedule B). Assessments included pharmacokinetic and pharmacodynamic profiles, as well as marker expression studies in pretreatment tumor biopsies. RESULTS: Forty patients received GSK461364: 23 patients in schedule A and 17 in schedule B. Dose-limiting toxicities (DLT) in schedule A at 300 mg (2 of 7 patients) and 225 mg (1 of 8 patients) cohorts included grade 4 neutropenia and/or grade 3-4 thrombocytopenia. In schedule B, DLTs of grade 4 pulmonary emboli and grade 4 neutropenia occurred at 7 or more days at 100 mg dose level. Venous thrombotic emboli (VTE) and myelosuppression were the most common grade 3-4, drug-related events. Pharmacokinetic data indicated that AUC (area under the curve) and C(max) (maximum concentration) were proportional across doses, with a half-life of 9 to 13 hours. Pharmacodynamic studies in circulating tumor cells revealed an increase in phosphorylated histone H3 (pHH3) following drug administration. A best response of prolonged stable disease of more than 16 weeks occurred in 6 (15%) patients, including 4 esophageal cancer patients. Those with prolonged stable disease had greater expression of Ki-67, pHH3, and Plk1 in archived tumor biopsies. CONCLUSIONS: The final recommended phase II dose for GSK461364 was 225 mg administered intravenously in schedule A. Because of the high incidence (20%) of VTE, for further clinical evaluation, GSK461364 should involve coadministration of prophylactic anticoagulation.