Alterations in regulatory T cells and immune checkpoint molecules in pancreatic cancer patients receiving FOLFIRINOX or gemcitabine plus nab-paclitaxel

PURPOSE This pilot study aimed on generating insight on alterations in circulating immune cells during the use of FOLFIRINOX and gemcitabine/nab-paclitaxel in pancreatic ductal adenocarcinoma (PDAC). PATIENTS AND METHODS Peripheral blood mononuclear cells were isolated before and 30~days after initiation of chemotherapy from 20 patients with advanced PDAC. Regulatory T cells (FoxP3+) and immune checkpoints (PD-1 and TIM-3) were analyzed by flow cytometry and immunological changes were correlated with clinical outcome. RESULTS Heterogeneous changes during chemotherapy were observed in circulating T-cell subpopulations with a pronounced effect on PD-1+ CD4+/CD8+ T cells. An increase in FoxP3+ or PD-1+ T cells had no significant effect on survival. An increase in TIM3+/CD8+ (but not TIM3+/CD4+) T cells was associated with a significant inferior outcome: median progression-free survival in the subgroup with an increase of TIM-3+/CD8+ T cells was 6.0 compared to 14.0~months in patients with a decrease/no change (p = 0.026); corresponding median overall survival was 13.0 and 20.0~months (p = 0.011), respectively. CONCLUSIONS Chemotherapy with FOLFIRNOX or gemcitabine/nab-paclitaxel induces variable changes in circulating T-cell populations that may provide prognostic information in PDAC

Proteomic Identification of the C/EBPalpha Multiprotein Complex Reveals That JNK1, an Activator of C/EBPalpha, Is Inactive in Acute Myeloid Leukemia.

Abstract CCAAT Enhancer Binding Protein Alpha (C/EBPalpha) is one of the key myeloid transcription factors whose function is impaired in Acute Myeloid Leukemia (AML). This is either due to mutation or inhibition by other proteins via protein-protein interaction. Here, we hypothesised that protein-protein interaction of C/EBPalpha with other proteins might be important for its activation. Based on our hypothesis, we analysed the multiprotein complex of C/EBPalpha. After GST-pull down from U937 nuclear extract and using a proteomic approach we were able to identify JNK1, PAK6, MADP, ZNF45 and others as interacting proteins of C/EBPalpha. Following confirmation of physical interaction of JNK1 with C/EBPalpha, we were able to show that JNK1 phosphorylates C/EBPalpha, increases its protein half-life and thereby enhances its transactivation and DNA binding capacity. However, in various AML subtypes, JNK1 mRNA and Phospho-JNK1 protein expression is downregulated as compared with normal bone marrow which is one of the possible reasons why C/EBPalpha is inactive in AML. Thus, here we report that C/EBPalpha is impaired in AML due to inactivation of JNK1.</jats:p

Proteomic Discovery of Max as a Novel Interacting Partner of C/EBPa: A Myc/Max/Mad Link.

Abstract In the present study, we sought to identify novel C/EBPa interacting proteins in vivo through immunoprecipitation using mass spectrometry-based proteomic techniques. We identified Max, a heterodimeric partner of Myc, as one of the interacting proteins of C/EBPa in our screen. We confirmed the in vivo interaction of C/EBPa with Max and showed that this interaction involves the basic region of C/EBPa. Endogenous C/EBPa and Max, but not Myc and Max co-localize in intranuclear structures during granulocytic differentiation of myeloid U937 cells. Max enhanced the transactivation capacity of C/EBPa on a minimal promoter. A chromatin-immunoprecipitation assay revealed occupancy of the human C/EBPa promoter in vivo by Max under cellular settings and by C/EBPa and Max under retinoic acid induced granulocytic differentiation. Interestingly, enforced expression of Max and C/EBPa, results in granulocytic differentiation of the human hematopoietic CD34+ cells as evidenced by CD11b and CD15 expression and by real-time PCR for various genes. Silencing of Max by short hairpin RNA in CD34+ and U937 cells strongly reduced the differentiation-inducing potential of C/EBPa, indicating the importance of C/EBPa-Max in myeloid progenitor differentiation. Taken together, our data reveal Max as a novel co-activator of C/EBPa functions thereby suggesting a possible link between CEBPa and Myc-Max-Mad network.</jats:p

Proteomic identification of the MYST domain histone acetyltransferase TIP60 (HTATIP) as a co-activator of the myeloid transcription factor C/EBPalpha.

The transcription factor C/EBPalpha (CEBPA) is a key player in granulopoiesis and leukemogenesis. We have previously reported the interaction of C/EBPalpha with other proteins (utilizing mass spectrometry) in transcriptional regulation. In the present study, we characterized the association of the MYST domain histone acetyltransferase Tat-interactive protein (TIP) 60 (HTATIP) with C/EBPalpha. We show in pull-down and co-precipitation experiments that C/EBPalpha and HTATIP interact. A chromatin immunoprecipitation (ChIP) and a confirmatory Re-ChIP assay revealed in vivo occupancy of the C/EBPalpha and GCSF-R promoter by HTATIP. Reporter gene assays showed that HTATIP is a co-activator of C/EBPalpha. The co-activator function of HTATIP is dependent on its intact histone acetyltransferase (HAT) domain and on the C/EBPalpha DNA-binding domain. The resulting balance between histone acetylation and deacetylation at the C/EBPalpha promoter might represent an important mechanism of C/EBPalpha action. We observed a lower expression of HTATIP mRNA in undifferentiated U937 cells compared to retinoic acid-induced differentiated U937 cells, and correlated expression of CEBPA and HTATIP mRNA levels were observed in leukemia samples. These findings point to a functional synergism between C/EBPalpha and HTATIP in myeloid differentiation and suggest that HTATIP might be an important player in leukemogenesis

Proteomic identification of C/EBP-DBD multiprotein complex: JNK1 activates stem cell regulator C/EBPalpha by inhibiting its ubiquitination.

Functional inactivation of transcription factors in hematopoietic stem cell development is involved in the pathogenesis of acute myeloid leukemia (AML). Stem cell regulator C/enhancer binding protein (EBP)alpha is among such transcription factors known to be inactive in AML. This is either due to mutations or inhibition by protein-protein interactions. Here, we applied a mass spectrometry-based proteomic approach to systematically identify putative co-activator proteins interacting with the DNA-binding domain (DBD) of C/EBP transcription factors. In our proteomic screen, we identified c-Jun N-terminal kinase (JNK) 1 among others such as PAK6, MADP-1, calmodulin-like skin proteins and ZNF45 as proteins interacting with DBD of C/EBPs from nuclear extract of myelomonocytic U937 cells. We show that kinase JNK1 physically interacts with DBD of C/EBP alpha in vitro and in vivo. Furthermore, we show that active JNK1 inhibits ubiquitination of C/EBP alpha possibly by phosphorylating in its DBD. Consequently, JNK1 prolongs C/EBP alpha protein half-life leading to its enhanced transactivation and DNA-binding capacity. In certain AML patients, however, the JNK1 mRNA expression and its kinase activity is decreased which suggests a possible reason for C/EBP alpha inactivation in AML. Thus, we report the first proteomic screen of C/EBP-interacting proteins, which identifies JNK1 as positive regulator of C/EBP alpha

Plasmodium falciparum Isolates in India Exhibit a Progressive Increase in Mutations Associated with Sulfadoxine-Pyrimethamine Resistance

The combination of sulfadoxine-pyrimethamine (SP) is used as a second line of therapy for the treatment of uncomplicated chloroquine-resistant Plasmodium falciparum malaria. Resistance to SP arises due to certain point mutations in the genes for the dihydrofolate reductase (DHFR) and dihydropteroate synthetase (DHPS) enzymes of the parasite. We have analyzed these mutations in 312 field isolates of P. falciparum collected from different parts of India to assess the effects of drug pressure. The rate of mutation in the gene for DHFR was found to be higher than that in the gene for DHPS, although the latter had mutations in more alleles. There was a temporal rise in the number of isolates with double dhfr mutations and single dhps mutations, resulting in an increased total number of mutations in the loci for DHFR and DHPS combined over a 5-year period. During these 5 years, the number of isolates with drug-sensitive genotypes decreased and the number of isolates with drug-resistant genotypes (double DHFR mutations and a single DHPS mutation) increased significantly. The number of isolates with the triple mutations in each of the genes for the two enzymes (for a total of six mutations), however, remained very low, coinciding with the very low rate of SP treatment failure in the country. There was a regional bias in the mutation rate, as isolates from the northeastern region (the state of Assam) showed higher rates of mutation and more complex genotypes than isolates from the other regions. It was concluded that even though SP is prescribed as a second line of treatment in India, the mutations associated with SP resistance continue to be progressively increasing

HSP90 inhibition overcomes ibrutinib resistance in mantle cell lymphoma.

The Bruton tyrosine kinase (BTK) inhibitor ibrutinib induces responses in 70% of patients with relapsed and refractory mantle cell lymphoma (MCL). Intrinsic resistance can occur through activation of the nonclassical NF-&kappa;B pathway and acquired resistance may involve the BTK C481S mutation. Outcomes after ibrutinib failure are dismal, indicating an unmet medical need. We reasoned that newer heat shock protein 90 (HSP90) inhibitors could overcome ibrutinib resistance by targeting multiple oncogenic pathways in MCL. HSP90 inhibition induced the complete degradation of both BTK and I&kappa;B kinase &alpha; in MCL lines and CD40-dependent B cells, with downstream loss of MAPK and nonclassical NF-&kappa;B signaling. A proteome-wide analysis in MCL lines and an MCL patient-derived xenograft identified a restricted set of targets from HSP90 inhibition that were enriched for factors involved in B-cell receptor and JAK/STAT signaling, the nonclassical NF-&kappa;B pathway, cell-cycle regulation, and DNA repair. Finally, multiple HSP90 inhibitors potently killed MCL lines in vitro, and the clinical agent AUY922 was active in vivo against both patient-derived and cell-line xenografts. Together, these findings define the HSP90-dependent proteome in MCL. Considering the disappointing clinical activity of HSP90 inhibitors in other contexts, trials in patients with MCL will be essential for defining the efficacy of and mechanisms of resistance after ibrutinib failure