Eomesodermin promotes a central memory phenotype in CD8+ T cells through the induction of IL-10

Following an immune response, a fraction of antigen-specific T cells persist as memory cells. Of these, central memory CD8+ T cells (TCM), which express secondary lymphoid organ-homing molecules and self-renew efficiently, are critical for maintaining long term memory. High levels of the T-box transcription factor Eomesodermin (Eomes) are associated with the TCM phenotype, but the mechanisms by which Eomes controls different aspects of TCM function are poorly understood. Using Eomes-knockout (EKO) CD8+ T cells, we demonstrate that Eomes regulates the expression of a number of TCM-associated markers including Bcl6, Ly6C and CD62L. In addition, we found that Eomes promotes the expression of IL-10 in activated CD8+ T cells. Interestingly, the addition of exogenous IL-10 was sufficient to upregulate CD62L expression in WT cells. Taken together, our data suggest that Eomes uses IL-10 to promote at least part of the central memory phenotype in CD8+ T cells. Consistent with this model, we find that TCM are secreting IL-10 in vivo, without additional re-stimulation. These findings warrant a modified model of TCM differentiation which includes distinct roles for Eomes and IL-10 in a T cell-intrinsic program driving TCM formation.

Abstract 363: STAT5 inhibition induces apoptosis in peripheral T cell lymphoma

Peripheral T cell lymphoma (PTCL) is a heterogeneous malignancy with extremely poor prognosis. Five-year overall survival is <40% and can be as low as 12% for specific subtypes. There is, therefore, an urgent need to identify and develop novel therapeutic targets and approaches. A number of recent sequencing studies, including a whole exome sequencing analysis of primary PTCL patients conducted by our laboratory, have revealed recurrent oncogenic driver mutations in the common gamma chain/JAK/STAT signaling pathway, resulting in the aberrant activation of the transcriptional regulator STAT5. STAT5 has additionally been found to be upregulated or contain activating mutations in 30-40% of PTCL cases of specific subtypes. These findings highlight STAT5 as an oncogenic driver of PTCL and suggest a role for it in novel therapeutic approaches. Based on these data, we aimed to evaluate STAT5 mechanistically as a therapeutic target in PTCL.

The drug, pimozide, which is an FDA approved neuroleptic agent, was recently identified by drug screen to be a STAT5 inhibitor. We assessed the efficacy of pimozide in PTCL using resazurin dye assay, Fluorescence Activated Cell Sorting (FACS), and immunoblot analysis. Our data demonstrate a concentration dependent reduction in STAT5 activity and the number of viable cells in PTCL cell lines after culture with pimozide. This is shown to be due to an increase in cell death by apoptosis. To verify that pimozide’s efficacy is due to its inhibition of STAT5 activity, we transduced PTCL cell lines with anti-STAT5 shRNA to knock down STAT5 and assessed PTCL cell survival and proliferation. We show that STAT5 knockdown results in a three-fold reduction in PTCL cell viability, which occurs due to an increase in apoptosis. Furthermore, our data supports a TRAIL dependent mechanism for induction of apoptosis shown by an upregulation of TRAIL by PTCL cells after STAT5 knockdown or culture with pimozide. Mitochondrial membrane potential is also disrupted. These findings have potential clinical implications, as we further demonstrate that pimozide inhibits STAT5 phosphorylation, reduces cell viability, and induces apoptosis in primary PTCL patient samples ex vivo.

This research supports further exploration of STAT5 as a therapeutic target in PTCL and the development of STAT5 inhibition in the treatment of PTCL. To facilitate the development of non-chemotherapeutic dependent therapeutic approaches for PTCL, we are now assessing STAT5 inhibition in combination with small molecule inducers of apoptosis including TRAIL pathway and PARP inhibitors. PARP inhibitors have shown efficacy in malignancies with DNA damage response pathway mutations, which have been identified in up to half of cases of certain subtypes of PTCL. We also aim to further investigate the use of JAK inhibitors, kinases responsible for STAT5 activation, in combination in PTCL, as several have demonstrated clinical efficacy in other hematologic malignancies.

Citation Format: Haley M. Simpson, Aki Furusawa, Kavitha Sadashivaiah, Arnob Banerjee. STAT5 inhibition induces apoptosis in peripheral T cell lymphoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 363. doi:10.1158/1538-7445.AM2017-363

Eomesodermin is required for antitumor immunity mediated by 4-1BB-agonist immunotherapy

CD8⁺ T cells in progressing tumors frequently fail to mount an effective antitumor response often in association with the expression of inhibitory receptors, including programmed cell death-1 (PD-1) and lymphocyte-activation gene 3 (Lag3). Using a lymphoma tumor model, we demonstrate that tumor-infiltrating CD8⁺ T cells from growing tumors co-express inhibitory receptors and co-stimulatory receptors, including 4-1BB (TNFRSF9) as well as high levels of 2 transcription factors, Eomesodermin (Eomes) and T-bet (Tbx21), critical determinants of CD8⁺ T cell fate. Immunotherapy with an agonistic anti-4–1-BB antibody altered the ratio of Eomes to T-bet expression in tumor-infiltrating CD8⁺ T cells by increasing Eomes and decreasing T-bet expression. 4-1BB-agonist immunotherapy was also associated with downregulated expression of the inhibitory receptors PD-1 and Lag3 on tumor-infiltrating CD8⁺ T cells, a molecular phenotype associated with subsequent attenuation of tumor growth. Furthermore, 4-1BB-agonist immunotherapy failed to effect tumor progression in mice with Eomes deficient T cells. However, upon resumption of tumor growth, tumor-infiltrating CD8⁺ T cells from treated animals continued to express high levels of Eomes as well as elevated levels of the inhibitory receptors PD-1 and Lag3. Our data suggest that tumor-infiltrating CD8⁺ T cells are poised between activation and inhibition as dictated by expression of both co-stimulatory receptors and inhibitory receptors and demonstrate that T cell expression of Eomes is necessary, but not sufficient, for efficacious 4-1BB-agonist-mediated immunotherapy.

Promising noninvasive cellular phenotype in prostate cancer cells knockdown of matrix metalloproteinase 9

Cell surface interaction of CD44 and MMP9 increases migration and invasion of PC3 cells. We show here that stable knockdown of MMP9 in PC3 cells switches CD44 isoform expression from CD44s to CD44v6 which is more glycosylated. These cells showed highly adhesive morphology with extensive cell spreading which is due to the formation of focal adhesions and well organized actin-stress fibers. MMP9 knockdown blocks invadopodia formation and matrix degradation activity as well. However, CD44 knockdown PC3 cells failed to develop focal adhesions and stress fibers; hence these cells make unstable adhesions. A part of the reason for these changes could be caused by silencing of CD44v6 as well. Immunostaining of prostate tissue microarray sections illustrated significantly lower levels of CD44v6 in adenocarcinoma than normal tissue. Our results suggest that interaction between CD44 and MMP9 is a potential mechanism of invadopodia formation. CD44v6 expression may be essential for the protection of non-invasive cellular phenotype. CD44v6 decrease may be a potential marker for prognosis and therapeutics.

Regulation of sealing ring formation by L-plastin and cortactin in osteoclasts

The aim of this study is to identify the exact mechanism(s) by which cytoskeletal structures are modulated during bone resorption. In this study, we have shown the possible role of different actin-binding and signaling proteins in the regulation of sealing ring formation. Our analyses have demonstrated a significant increase in cortactin and a corresponding decrease in L-plastin protein levels in osteoclasts subjected to bone resorption for 18 h in the presence of RANKL, M-CSF, and native bone particles. Time-dependent changes in the localization of L-plastin (in actin aggregates) and cortactin (in the sealing ring) suggest that these proteins may be involved in the initial and maturation phases of sealing ring formation, respectively. siRNA to cortactin inhibits this maturation process but not the formation of actin aggregates. Osteoclasts treated as above but with TNF-α demonstrated very similar effects as observed with RANKL. Osteoclasts treated with a neutralizing antibody to TNF-α displayed podosome-like structures in the entire subsurface and at the periphery of osteoclast. It is possible that TNF-α and RANKL-mediated signaling may play a role in the early phase of sealing ring configuration (i.e. either in the disassembly of podosomes or formation of actin aggregates). Furthermore, osteoclasts treated with alendronate or αv reduced the formation of the sealing ring but not actin aggregates. The present study demonstrates a novel mechanistic link between L-plastin and cortactin in sealing ring formation. These results suggest that actin aggregates formed by L-plastin independent of integrin signaling function as a core in assembling signaling molecules (integrin αvβ3, Src, cortactin, etc.) involved in the maturation process.

Evaluation of intra-uterine contraception in selected mission hospitals in India

Intra-uterine contraception is a useful method of fertility control, because of its applicability at all levels of socio-economic development and it has been the mainstay of the fertility control programme in many countries.

The present evaluation is based on the hospital follow-up records of 4067 IUD cases from randomly selected mission hospitals for the years 1967 and 1968. Of the insertions, 97·7% were non-post-partum, and 60% of the acceptors were from the age group 25–34 years with a median age of 29·8 years; nearly 70% had fewer than four living children. The pattern of distribution by religion is similar to that of the 1961 census figures.

The average number of women months (6·7) of IUD use is very low in a follow-up study of 24 months but is more or less consistent, both by age and parity.

The incidence of expulsion, removal and pregnancy was 8·2, 12·9 and 0·6 respectively for all ages and although these rates were higher with the 27½-mm loop than the 30-mm loop the differences are not statistically significant.

The rates of expulsion, removals and complaints were greatest during the first 6 months of use and decreased gradually with increase in duration of use.

Bleeding, or other symptoms associated with bleeding, were the main reasons for the removals.

Incidence of re-insertion was higher among those aged <25 years than among those aged ≥25 years and the difference in the proportion of re-insertions between the two age groups is statistically significant.

The size of the loop seems to have no bearing on the incidence of re-insertions.

Total termination rates at the end of 6, 12, 18 and 24 months were 9·9, 15·2, 25·0 and 55·9 per 100 first insertions respectively.