Targeting the Inducible T-cell Costimulator (ICOS) in Patients with Relapsed/Refractory T-follicular Helper Phenotype Peripheral T-cell and Angioimmunoblastic T-cell Lymphoma.

PURPOSE: Proliferation of T-follicular helper (TFH) CD4+ T cells is a postulated pathogenic mechanism for T-cell non-Hodgkin lymphomas (T-NHL). The inducible T-cell costimulator (ICOS) is highly expressed by TFH, representing a potential target. MEDI-570 is a monoclonal antibody against ICOS, which eliminates ICOS+ cells in preclinical models. PATIENTS AND METHODS: We report the safety, pharmacokinetics (PK), pharmacodynamics (PD), and clinical activity of MEDI-570 in T-NHL. NCI-9930 is a phase I, first-in-human study of MEDI-570 in relapsed/refractory malignant T-NHL known to express ICOS. MEDI-570 was administered intravenously every 3 weeks for up to 12 cycles. Primary endpoints were safety, dose-limiting toxicities (DLT), and recommended phase II dose (RP2D). Secondary and exploratory endpoints included efficacy parameters and various correlative studies. This study is supported by the National Cancer Institute (NCT02520791). RESULTS: Twenty-three patients were enrolled and received MEDI-570 at five dose levels (0.01-3 mg/kg). Sixteen (70%) had angioimmunoblastic T-cell lymphoma (AITL); median age was 67 years (29-86) and the median prior lines of therapies was 3 (1-16). Most common grade 3 or 4 adverse events were decreased CD4+ T cells (57%), lymphopenia (22%), anemia (13%), and infusion-related reactions (9%). No DLTs were observed. The RP2D was determined at 3 mg/kg. Analysis of T-cell subsets showed reductions in CD4+ICOS+ T cells reflecting its effects on TFH cells. The response rate in AITL was 44%. CONCLUSIONS: MEDI-570 was well tolerated and showed promising clinical activity in refractory AITL. MEDI-570 resulted in sustained reduction of ICOS+ T lymphocytes.

Liver kinase B1 expression (LKB1) is repressed by estrogen receptor alpha (ERα) in MCF-7 human breast cancer cells.

BACKGROUND: Liver kinase 1 (LKB1) is emerging as a multifunctional protein, acting as a key metabolic enzyme, regulator of cell polarity, and transcription factor. Altered LKB1 expression has been linked with various cancers and may be a potential prognostic marker. While the functional role of LKB1 continues to undergo intensive investigation, the molecular mechanisms that regulate its expression remain to be defined more clearly. Recent reports have established a possible link between estrogen receptor alpha (ERα) signaling and LKB1 in MCF-7 human breast cancer cells. The current study aimed to investigate whether LKB1 is transcriptionally regulated by ERα in MCF-7 cells. METHODS: siRNA transfections were used to transiently knock down LKB1 and ERα. LKB1 and ERα mRNA and protein levels were evaluated by real-time PCR and Western blotting, respectively. An approximately 3 kilobase pair human LKB1 promoter construct and various truncations were generated, transfected into MCF-7 cells, and luciferase reporter assays were performed. Cells were also treated with various doses of 17-ß-estradiol (E2) to evaluate the effect on LKB1 and ERα mRNA levels. RESULTS: LKB1 mRNA and protein levels were significantly lower in ERα-positive MCF-7 compared to ERα-negative MDA-MB-231 breast cancer cells, suggesting that ERα may act as a repressor. siRNA-mediated knock-down of ERα in MCF-7 cells significantly increased LKB1 promoter activity and expression at the mRNA and protein levels, and computational analysis revealed the presence of several putative estrogen response element (ERE) DNA binding sites in the LKB1 promoter region. In addition, treatment with E2 led to an increase in LKB1 expression, concomitant with decreased expression of ERα in MCF-7 cells. The E2-mediated increase was abrogated by pretreatment with actinomycin D, supporting that the observed changes in LKB1 levels were transcriptionally regulated. CONCLUSIONS: ERα repressively modulates the expression of LKB1 at the transcriptional level. Targeting the expression of LKB1 by modulating ERα signaling may provide a potential approach to further evaluate its function in ERα-positive breast cancers.

Establishing a relationship between prolactin and altered fatty acid ß-oxidation via carnitine palmitoyl transferase 1 in breast cancer cells.

BACKGROUND: Mammary carcinomas have been associated with a high-fat diet, and the rate of breast cancer in overweight post-menopausal women is up to 50% higher than in their normal-weight counterparts. Epidemiological studies suggest that prolactin (PRL) plays a role in the progression of breast cancer. The current study examined breast cancer as a metabolic disease in the context of altered fatty acid catabolism by examining the effect of PRL on carnitine palmitoyl transferase 1 (CPT1), an enzyme that shuttles long-chain fatty acids into the mitochondrial matrix for ß-oxidation. The effect of PRL on the adenosine 5'-monophosphate-activated protein kinase (AMPK) energy sensing pathway was also investigated. METHODS: MCF-7 and MDA-MB-231 breast cancer cells and 184B5 normal breast epithelial cells treated with 100 ng/ml of PRL for 24 hr were used as in vitro models. Real-time PCR was employed to quantify changes in mRNA levels and Western blotting was carried out to evaluate changes at the protein level. A non-radioactive CPT1 enzyme activity assay was established and siRNA transfections were performed to transiently knock down specific targets in the AMPK pathway. RESULTS: PRL stimulation increased the expression of CPT1A (liver isoform) at the mRNA and protein levels in both breast cancer cell lines, but not in 184B5 cells. In response to PRL, a 20% increase in CPT1 enzyme activity was observed in MDA-MB-231 cells. PRL treatment resulted in increased phosphorylation of the α catalytic subunit of AMPK at Thr172, as well as phosphorylation of acetyl-CoA carboxylase (ACC) at Ser79. A siRNA against liver kinase B1 (LKB1) reversed these effects in breast cancer cells. PRL partially restored CPT1 activity in breast cancer cells in which CPT1A, LKB1, or AMPKα-1 were knocked down. CONCLUSIONS: PRL enhances fatty acid ß-oxidation by stimulating CPT1 expression and/or activity in MCF-7 and MDA-MB-231 breast cancer cells. These PRL-mediated effects are partially dependent on the LKB1-AMPK pathway, although the regulation of CPT1 is also likely to be influenced by other mechanisms. Ultimately, increased CPT1 enzyme activity may contribute to fueling the high energy demands of cancer cells. Targeting metabolic pathways that are governed by PRL, which has already been implicated in the progression of breast cancer, may be of therapeutic benefit.