SET oncoprotein overexpression in B-cell chronic lymphocytic leukemia and non-Hodgkin lymphoma: a predictor of aggressive disease and a new treatment target.

B-cell chronic lymphocytic leukemia (CLL), an incurable leukemia, is characterized by defective apoptosis. We found that the SET oncoprotein, a potent inhibitor of the protein phosphatase 2A (PP2A) tumor suppressor, is overexpressed in primary CLL cells and B-cell non-Hodgkin lymphoma (NHL) cell line cells. In CLL, increased levels of SET correlated significantly with disease severity (shorter time to treatment and overall survival). We developed SET antagonist peptides that bound SET, increased cellular PP2A activity, decreased Mcl-1 expression, and displayed selective cytotoxicity for CLL and NHL cells in vitro. In addition, shRNA for SET was cytotoxic for NHL cells in vitro. The SET antagonist peptide COG449 inhibited growth of NHL tumor xenografts in mice. These data demonstrate that SET is a new treatment target in B-cell malignancies and that SET antagonists represent novel agents for treatment of CLL and NHL.

Perifosine treatment in chronic lymphocytic leukemia: results of a phase II clinical trial and in vitro studies.

Abstract Because of the importance of the phosphoinositide 3-kinase (PI3K)/AKT pathway in chronic lymphocytic leukemia (CLL), we evaluated in vitro cytotoxicity induced by perifosine, an AKT inhibitor, in CLL lymphocytes and found that the mean 50% effective dose (ED50) was 313 nM. We then performed a phase II trial of perifosine in patients with relapsed/refractory CLL to assess response, outcomes, toxicity and ex vivo correlative measures. After 3 months of treatment, six of eight patients showed stable disease, one achieved a partial response and one had progressive disease. Median event-free survival and overall survival in all patients treated were 3.9 and 9.7 months. Adverse events included hematologic, infectious/fever, pain, gastrointestinal and constitutional toxicities. Unexpectedly, AKT phosphorylation in CLL lymphocytes from treated patients was not correlated with response. Additionally, perifosine did not inhibit AKT phosphorylation in cultured CLL lymphocytes. Perifosine is cytotoxic to CLL cells in vitro, and largely induces stabilized disease in vivo, with an AKT-independent mechanism.

Phase II study of cenersen, an antisense inhibitor of p53, in combination with fludarabine, cyclophosphamide and rituximab for high-risk chronic lymphocytic leukemia.

Patients with chronic lymphocytic leukemia (CLL) with deletion or mutation of TP53 have exceedingly poor clinical outcomes. Cenersen, an oligonucleotide targeting TP53, has been shown to abrogate the activity of TP53 gain-of-function mutants and to increase sensitivity of lymphoma cells to cytotoxic chemotherapy in vitro. We combined cenersen with fludarabine, cyclophosphamide and rituximab (FCR) as treatment for patients with high-risk CLL. The purpose of this phase II study was to determine the overall response rate, response duration and toxicity of cenersen administered in combination with FCR. Twenty patients with relapsed or high-risk CLL were evaluated. Nineteen patients were previously treated. The complete response rate was 18%; the overall response rate was 53%. Median progression-free and overall survival was 5.3 and 10.6 months, respectively. The most common serious adverse events were neutropenia and thrombocytopenia. In this single arm phase II study, cenersen combined with FCR yielded clinical responses with acceptable toxicity in patients with high-risk CLL.