Prostate cancer is the most common type of cancer diagnosed and the second leading cause of cancer-related death in American men. Natural Killer (NK) cells are the first line of defense against cancer and infections. NK cell function is regulated by a delicate balance between signals received through activating and inhibitory receptors. Previously, we identified Lectin-like transcript-1 (LLT1/OCIL/CLEC2D) as a counter-receptor for the NK cell inhibitory receptor NKRP1A (CD161). Interaction of LLT1 expressed on target cells with NKRP1A inhibits NK cell activation. In this study, we have found that LLT1 was overexpressed on prostate cancer cell lines (DU145, LNCaP, 22Rv1 and PC3) and in primary prostate cancer tissues both at the mRNA and protein level. We further showed that LLT1 is retained intracellularly in normal prostate cells with minimal cell surface expression. Blocking LLT1 interaction with NKRP1A by anti-LLT1 mAb on prostate cancer cells increased the NK-mediated cytotoxicity of prostate cancer cells. The results indicate that prostate cancer cells may evade immune attack by NK cells by expressing LLT1 to inhibit NK cell-mediated cytolytic activity through LLT1-NKRP1A interaction. Blocking LLT1-NKRP1A interaction will make prostate cancer cells susceptible to killing by NK cells and therefore may be a new therapeutic option for treatment of prostate cancer.

Acute lymphoblastic leukemia (ALL) represents the most common pediatric cancer. Most patients (85%) develop B-cell ALL; however, T-cell ALL tends to be more aggressive. We have previously identified 2B4 (SLAMF4), CS1 (SLAMF7) and LLT1 (CLEC2D) that can activate or inhibit NK cells upon the interaction with their ligands. In this study, the expression of 2B4, CS1, LLT1, NKp30 and NKp46 was determined. The expression profiles of these immune receptors were analyzed in the peripheral blood mononuclear cells of B-ALL and T-ALL subjects by single-cell RNA sequencing data obtained from the St. Jude PeCan data portal that showed increased expression of LLT1 in B-ALL and T-ALL subjects. Whole blood was collected from 42 pediatric ALL subjects at diagnosis and post-induction chemotherapy and 20 healthy subjects, and expression was determined at the mRNA and cell surface protein level. A significant increase in cell surface LLT1 expression in T cells, monocytes and NK cells was observed. Increased expression of CS1 and NKp46 was observed on monocytes of ALL subjects at diagnosis. A decrease of LLT1, 2B4, CS1 and NKp46 on T cells of ALL subjects was also observed post-induction chemotherapy. Furthermore, mRNA data showed altered expression of receptors in ALL subjects pre- and post-induction chemotherapy treatment. The results indicate that the differential expression of the receptors/ligand may play a role in the T-cell- and NK-cell-mediated immune surveillance of pediatric ALL.

Chronic lymphocytic leukemia (CLL) is the most common type of leukemia in western countries and typically occurs in elderly individuals. There will be an estimated 21,250 newly diagnosed cases in the United States this year and 4,320 deaths. Due to the highly variable clinical course of this disease, prognostication and risk stratification methods are necessary for guiding decisions on clinical management. Integrated prognostic models incorporating laboratory testing for multiple molecular, cytogenetic, and other biomarkers have recently been proposed by major clinical guidelines to classify patients into risk subgroups. The current NCCN Guidelines for Chronic Lymphocytic Leukemia/Small Lymphocytic Leukemia describe such an integrated prognostic model known as the Rossi model that includes TP53, NOTCH1, SF3B1, and BIRC3 mutations along with the cytogenetic abnormalities detected by fluorescence in situ hybridization (FISH) to classify CLL patients into 4 distinct prognostic subgroups: high-risk (TP53 and/or BIRC3 abnormalities), intermediate-risk (NOTCH1 and/or SF3B1 mutations and/or deletion 11q), low-risk (trisomy 12 and wild-type for all genetic lesions), and very low-risk (deletion 13q only). The 10-year survival rates for these subgroups are 29%, 37%, 57%, and 69%, respectively. To assess the clinical value of an integrated biomarker testing approach, we analyzed results of 651 consecutive cases submitted to our clinical diagnostic laboratory for testing on our integrated panel of molecular and cytogenetic biomarkers for CLL. Our panel includes detection of genomic alterations by FISH (deletion 6q, 13q, 11q, 17p, trisomy 12, IGH rearrangement, and IGH/CCND1 translocation) and detection of sequence variants in BIRC3, BTK, MYD88, NOTCH1, PCLG2, SF3B1, and TP53 by next-generation sequencing (NGS). In total, 472 cases had positive findings by either FISH (90%) or NGS (46%) for a detection rate of 72.5%. Using the Rossi integrated prognostic model, 17.5% of cases fell into the high-risk subgroup, 20% of cases fell into the intermediate-risk subgroup, 43.5% of cases fell into the low-risk subgroup, and 19% of cases fell into the very low-risk subgroup. Importantly, among cases with positive FISH findings, 40.1% of cases also had positive molecular findings. In approximately 84% of cases belonging to the low-risk cytogenetic subgroups by FISH assessment alone, the incorporation of molecular findings resulted in reclassification into a higher-risk subgroup. Among the FISH-negative cases, 17% were classified as high-risk or intermediate-risk based on the molecular findings. Together, these findings support the clinical value of an integrative biomarker testing approach that includes both molecular and cytogenetic biomarkers to stratify CLL patients into risk subgroups to help guide decisions on clinical management. Disclosures Prathapam: Quest Diagnostics: Current Employment. Maharjan: Quest Diagnostics: Current Employment. Powers: Quest Diagnostics: Current Employment. Freitas: Quest Diagnostics: Current Employment. Sun: Quest Diagnostics: Current Employment. Tan: Quest Diagnostics: Current Employment. Gupta: Quest Diagnostics: Current Employment. Hucthagowder: Quest Diagnostics: Current Employment. Graham: Quest Diagnostics: Current Employment. Whitman: Quest Diagnostics: Current Employment. Khadgi: Quest Diagnostics: Current Employment. Daniel: Quest Diagnostics: Current Employment. Racke: Quest Diagnostics: Current Employment. Champion: Quest Diagnostics: Current Employment.