LIGHT (TNFSF14) Costimulation Enhances Myeloid Cell Activation and Antitumor Immunity in the Setting of PD-1/PD-L1 and TIGIT Checkpoint Blockade

Coinhibition of TIGIT (T cell immunoreceptor with Ig and ITIM domains) and PD-1/PD-L1 (PD-1/L1) may improve response rates compared with monotherapy PD-1/L1 blockade in checkpoint naive non-small cell lung cancer with PD-L1 expression >50%. TIGIT mAbs with an effector-competent Fc can induce myeloid cell activation, and some have demonstrated effector T cell depletion, which carries a clinical liability of unknown significance. TIGIT Ab blockade translates to antitumor activity by enabling PVR signaling through CD226 (DNAM-1), which can be directly inhibited by PD-1. Furthermore, DNAM-1 is downregulated on tumor-infiltrating lymphocytes (TILs) in advanced and checkpoint inhibition-resistant cancers. Therefore, broadening clinical responses from TIGIT blockade into PD-L1low or checkpoint inhibition-resistant tumors, may be induced by immune costimulation that operates independently from PD-1/L1 inhibition. TNFSF14 (LIGHT) was identified through genomic screens, in vitro functional analysis, and immune profiling of TILs as a TNF ligand that could provide broad immune activation. Accordingly, murine and human bifunctional fusion proteins were engineered linking the extracellular domain of TIGIT to the extracellular domain of LIGHT, yielding TIGIT-Fc-LIGHT. TIGIT competitively inhibited binding to all PVR ligands. LIGHT directly activated myeloid cells through interactions with LTβR (lymphotoxin β receptor), without the requirement for a competent Fc domain to engage Fcγ receptors. LIGHT costimulated CD8+ T and NK cells through HVEM (herpes virus entry mediator A). Importantly, HVEM was more widely expressed than DNAM-1 on T memory stem cells and TILs across a range of tumor types. Taken together, the mechanisms of TIGIT-Fc-LIGHT promoted strong antitumor activity in preclinical tumor models of primary and acquired resistance to PD-1 blockade, suggesting that immune costimulation mediated by LIGHT may broaden the clinical utility of TIGIT blockade.

494 Phase 1 dose escalation and dose expansion study of an agonist redirected checkpoint (ARC) fusion protein, SL-279252 (PD1-Fc-OX40L), in subjects with advanced solid tumors or lymphomas

Background

PD1-Fc-OX40L, is a hexameric, bi-functional fusion protein with an extracellular domain (ECD) of PD-1 (70 pM affinity to PD-L1) linked to the ECD of OX40L (324 pM affinity to OX40) through an Fc linker. The therapeutic activity of mPD1-Fc-OX40L in murine tumors was superior to PD1 blocking, OX40 agonist or combination antibody therapy.1

Methods

The first-in-human, Phase 1 dose escalation study is evaluating SL-279252 as monotherapy in patients (pts) with advanced solid tumors or lymphomas. Objectives include evaluation of safety, dose-limiting toxicity (DLT), recommended phase 2 dose (RP2D), pharmacokinetic (PK) parameters, pharmacodynamic (PD) effects, and anti-tumor activity per iRECIST.

Results

As of 11 June 2021, 43 pts were enrolled and dosed intravenously with SL-279252 (median age 64 years; 56% male; median [range] of 3 [0–5] prior systemic therapies for metastatic disease): 30 pts were treated on schedule 1 (day 1, 8, 15, 29, then every 2 weeks ) from dose level 0.0001–6 mg/kg, and 13 pts treated on schedule 2 (weekly) from dose level 0.3–3 mg/kg. 58% of pts were PD-1/L1 inhibitor experienced, and most tumors lacked PD-L1 expression. Common (>15%) treatment emergent adverse events (AEs) of any grade (G) were constipation in 11 (26%) pts, back pain 8 (19%) pts, anemia 7 (16%) pts and decreased appetite 7 (16%) pts. Infusion-related reactions (G1/2) were noted in 3 (7%) pts. G3 treatment-related AEs (TRAEs) were neutropenia (2%) and hypercalcemia (2%); no G4/5 TRAEs or DLTs occurred. SL-279252 Cmax and AUC increased linearly up to 3mg/kg, and greater than proportional increase in AUC was observed at 6 mg/kg. The preliminary T½ was ~23 hours. Dose-dependent receptor occupancy on CD4+OX40+ T cells persisted for >7 days and these cells rapidly marginated from the peripheral blood post infusion. Increases in the number of proliferating central and/or effector memory T cells were seen in some pts at doses of ≥1mg/kg. Analysis of paired tumor biopsies is ongoing. Best response was 1 durable confirmed iPR (ocular melanoma, 4 prior systemic regimens) in a pt who remained on treatment for >1 yr, and iSD in 12 pts (1 unconfirmed iPR). iSD for > 24 wks occurred in 6/12 pts.

Conclusions

SL-279252 is well-tolerated in pts with refractory solid tumors with no maximum tolerated dose (MTD) reached. OX40-dependent PD effects and durable anti-tumor activity was observed. Trends for PK/PD effects at ≥1 mg/kg suggests dose exploration in PD-L1 expressing cancers is warranted beyond 6 mg/kg.

Acknowledgements

Thanks are extended to study participants; Takeda Pharmaceutical Company, Boston, MA, United States; Cathrine Leonowens, PhD, Nuventra Pharma Sciences, Durham, NC, United States and Cadence Communications and Research, Thousand Oaks, CA, United States. This study is funded by Shattuck Labs, Inc. Austin, TX and Durham, NC, United States.

Trial Registration

NCT03894618

References

Fromm G, de Silva S, Johannes K, Patel A, Hornblower JC, Schreiber TH. Agonist redirected checkpoint, PD1-Fc-OX40L, for cancer immunotherapy. J Immunother Cancer 2018;6: 1–16.

Ethics Approval

This study is being conducted in full conformity with the Declaration of Helsinki and was approved by all IRBs/ethics committees from each clinical site participating in the study. Specific approval numbers can be provided upon request.

3 Development of an integrated method to quantify receptor occupancy for agonist immunotherapeutics that stimulate target cells to migrate from the peripheral blood

Background

One of the pharmacodynamic measures of biologic compounds is an assessment of target receptor/ligand occupancy (RO). If the primary mechanism for drug clearance is through target binding, drug exposure may increase once RO is saturated. SL-172154 (SIRPα-Fc-CD40L) and SL-279252 (PD1-Fc-OX40L) are two bi-functional fusion proteins in phase I clinical trials (NCT04406623 and NCT03894618). The binding interaction between a biologic compound and its targets (CD47 or PD-L1) typically does not stimulate migration from the blood, allowing direct measurement of drug and target. Evaluation of RO for immune agonists (CD40 and OX40) is challenging because agonists can stimulate lymphocytes to rapidly extravasate from the peripheral blood following infusion, thus precluding direct RO measurement as target cells are no longer present in the blood (figure 1a).

Methods

To assess full receptor engagement of CD40 or OX40, the formula shown in figure 1b was derived. The formula captures cells that rapidly migrated from the blood, combined with those that remained in the blood within 2 hours post infusion using multiparameter FACS analysis. SAS JMP was used to calculate and visualize all parameters.

Results

Within 2 hours of SL-172154 infusion at 1 mg/kg (n=3), CD40+ B cell counts decreased from a pre-dose average by 87%. Of the CD40+ B cells remaining in the blood, ~95% were bound with SL-172154. CD40+ B cell counts recovered in the blood by the next dose, and as counts increased so did the proportion of cells that were bound with SL-172154. Similarly, within 2 hours of SL-279252 infusion at 1 mg/kg (n=10), CD4+OX40+ T cell counts decreased from a pre-dose average by 41.5% (range 0 – 70%). Of the CD4+OX40+ cells remaining in the blood, ~32% were bound with SL-279252. CD4+OX40+ cells returned to pre-treatment numbers over a 7-day interval and nearly all cells remained bound with SL-279252. Taken together, these data demonstrate that a large proportion of CD40+ (SL-172154) or OX40+ (SL-279252) cells bind drug immediately post infusion, migrate from the blood, and slowly return to the blood with drug still bound to the cell surface.

Abstract 3 Figure 1

CD4+ OX40+ T cells and SL-279252

Conclusions

Administration of SL-172154 (CD40) and SL-279252 (OX40) stimulated rapid egress of target cells from the blood. An integrated assessment, termed ‘receptor engagement’, was developed to derive RO both on circulating cells and those that rapidly marginated. When CD40+ or OX40+ cells returned to the blood, they remained drug-bound, indicating that the compounds may piggy-back on target cells into tissues.

Acknowledgements

Thanks are extended to study participants; Takeda Pharmaceutical Company, Boston, MA, United States; Cathrine Leonowens, PhD, Nuventra Pharma Sciences, Durham, NC, United States and Cadence Communications and Research, Thousand Oaks, CA, United States. This study is funded by Shattuck Labs, Inc. Austin, TX and Durham, NC, USA

Ethics Approval

This study is being conducted in full conformity with the Declaration of Helsinki and was approved by all IRBs/ethics committees from each clinical site participating in the study. Specific approval numbers can be provided upon request.

429 Phase 1 dose escalation study of the agonist redirected checkpoint, SL-172154 (SIRPα-Fc-CD40L) in subjects with platinum-resistant ovarian cancer

Background

SIRPα-Fc-CD40L is a hexameric, bi-functional fusion protein consisting of SIRPα (binding affinity to CD47 is 0.628 nM) linked to CD40L (binding affinity to CD40 is 4.74 nM) through an Fc linker protein.1 By augmenting antigen processing and promoting antigen presenting cell (APC) maturation, this molecule is designed to bridge innate and adaptive immunity, enhancing tumor cell phagocytosis and antigen cross-presentation to CD8 T cells.

Methods

The first-in-human, Phase 1 dose escalation study is evaluating SL-172154 as monotherapy in patients (pts) with platinum resistant ovarian, fallopian tube and primary peritoneal cancers. Objectives include evaluation of safety, dose-limiting toxicity (DLT) and recommended phase 2 dose (RP2D), pharmacokinetic (PK) parameters, pharmacodynamic (PD) effects and antitumor activity based on RECIST.

Results

As of 6 July 2021, 14 heavily pretreated pts (median age, 67 years) were enrolled and treated with intravenous (IV) administration of SL-172154 across 4 dose levels on 2 schedules: schedule 1 (day 1, 8, 15, 29, Q2 weeks) at 0.1, 0.3 mg/kg and schedule 2 (weekly) at 0.3, 1.0, 3.0 mg/kg. The most common treatment-related (>20%) adverse events (AEs) of any grade (G) were fatigue (n=7, 50%), infusion-related reactions (IRR) (n=6, 43%), nausea (n=4, 29%), and decreased appetite (n=3, 21%). Treatment-related IRRs (G1/G2) generally occurred near the end of infusion or immediately post-infusion; the full dose was able to be delivered in each IRR event, and subsequent infusions in patients having IRRs were managed with pre-medications. No treatment related ≥G3 AEs or DLTs have occurred. CD47 receptor occupancy (RO) on leukocytes approached 90% at 1.0 and 3.0 mg/kg. Minimal binding to CD47+ red blood cells was observed at all dose levels. CD40 RO on B cells was >60% at doses ≥0.1 mg/kg and 75%–100% at 1.0 and 3.0 mg/kg. Rapid, transient B cell and monocyte margination was observed following infusion of SL-172154 and was consistent with dose-dependent increases in IL-12, MCP-1, MIP-1β, MIP-1α, and MDC. No appreciable increases in IL-6 or TNFα were noted and there was no correlation between IRRs and cytokine increases. Among 12 evaluable pts, the best response was stable disease in 3 pts.

Conclusions

SL-172154 has been well tolerated with no evidence of anemia, thrombocytopenia, liver dysfunction or cytokine release syndrome. A unique serum cytokine signature consistent with CD40 RO and activation has been observed and this signature is maintained following repeat dosing. Dose escalation is ongoing.

Acknowledgements

Thanks are extended to study participants; Cathrine Leonowens, PhD, Nuventra Pharma Sciences, Durham, NC, United States and Cadence Communications and Research, Thousand Oaks, CA, United States. This study is funded by Shattuck Labs, Inc. Austin, TX and Durham, NC, United States.

Trial Registration

NCT04406623

References

de Silva S, Fromm G, Shuptrine CW, Johannes K, Patel A, Yoo KJ, et al. CD40 enhances type I interferon responses downstream of CD47 blockade, bridging innate and adaptive immunity. Cancer Immunol Res 2020; 8: 230–245.

Ethics Approval

This study is being conducted in full conformity with the Declaration of Helsinki and was approved by all IRBs/ethics committees from each clinical site participating in the study. Specific approval numbers can be provided upon request.

Abstract 1697: The development of an in vivo model of checkpoint acquired resistance, reveals a program of interferon hyperstimulation, resulting in dysregulation of MHC class I, protein translation/trafficking, and other unique pathways, that may be useful for guiding clinical strategy in patients with phenotypic similarities

Approximately 20-40% of cancer patients who initially benefit from PD-1/L1 checkpoint blockade later develop progressive disease, which is associated with genetic and/or phenotypic changes in tumor cells that enable acquired resistance. Tumors from patients who have developed acquired resistance to checkpoint blockade (CPI-AR) typically demonstrate downregulation of specific antigens or proteins involved in antigen presentation on MHC class I, and dysregulation of interferon response pathways. With increasing CPI use across a large number of tumor types, the proportion of cancer patients with CPI-AR is increasing. Pre-clinical tumor models which mimic CPI-AR in humans are needed. We generated in vivo CPI-AR tumor models by serially passaging common CPI responsive murine syngeneic tumor cell lines (i.e. CT26) in vivo, followed by the excision and ex vivo expansion of the tumors that failed to respond to anti-PD1. This was repeated until passaged tumors no longer responded to anti-PD1 therapy. Transcriptomes of CT26 parental, CT26/CPI-AR, and B16.F10 melanoma (considered CPI primary resistant, CPI-PR) tumors were sequenced either under normal culture conditions or following 24 hour exposure to IFNg to assess interferon responsiveness. Here we present the genomic characterization of the CPI -PR and -AR models. Paradoxically, CPI-AR tumors maintain a state of type I/II IFN gene hyperactivation and increased expression of genes involved in MHC class I mediated antigen presentation/processing. Despite this transcriptional hyperactivity, CPI-AR tumor cells have a decreased capacity to translate and traffic these associated proteins to the cell membrane. Interestingly, upon challenge with IFNg, CPI-AR tumors down-regulate gene expression for PD-L1, TAP1, TAP2, β2M and other key pathways typically up-regulated by IFN stimulation. Collectively, the CPI-AR and -PR tumor models reflect many of the genomic and phenotypic changes reported in CPI-AR cancer patients. The CT26/CPI-AR tumors reproduce a state of IFN hypo-responsiveness and genetic/protein dysregulation. These clinically relevant models can be used to screen therapeutics that may translate to meaningful benefit for CPI-AR cancer patients.

Citation Format: George J. Fromm, Danish Memon, Suresh de Silva, Kyung Jin Yoo, Kellsey Johannes, Casey Shuptrine, Jaya Miriyala, Arpita Patel, Fatima Rangwala, Zachary Opheim, Thuy-Ai Nguyen, Louis Gonzalez, Fatima Rangwala, Taylor H. Schreiber, Matthew D. Hellmann, Martin L. Miller, Taylor H. Schreiber. The development of an in vivo model of checkpoint acquired resistance, reveals a program of interferon hyperstimulation, resulting in dysregulation of MHC class I, protein translation/trafficking, and other unique pathways, that may be useful for guiding clinical strategy in patients with phenotypic similarities [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1697.

BRAF-Mutant Transcriptional Subtypes Predict Outcome of Combined BRAF, MEK, and EGFR Blockade with Dabrafenib, Trametinib, and Panitumumab in Patients with Colorectal Cancer

PURPOSE

The influence of the transcriptional and immunologic context of mutations on therapeutic outcomes with targeted therapy in cancer has not been well defined. BRAF V600E-mutant (BM) colorectal cancer comprises two main transcriptional subtypes, BM1 and BM2. We sought to determine the impact of BM subtype, as well as distinct biological features of those subtypes, on response to BRAF/MEK/EGFR inhibition in patients with colorectal cancer.

PATIENTS AND METHODS

Paired fresh tumor biopsies were acquired at baseline and on day 15 of treatment from all consenting patients with BM colorectal cancer enrolled in a phase II clinical trial of dabrafenib, trametinib, and panitumumab. For each sample, BM subtype, cell cycle, and immune gene signature expression were determined using RNA-sequencing (RNA-seq), and a Cox proportional hazards model was applied to determine association with progression-free survival (PFS).

RESULTS

Confirmed response rates, median PFS, and median overall survival (OS) were higher in BM1 subtype patients compared with BM2 subtype patients. Evaluation of immune contexture identified greater immune reactivity in BM1, whereas cell-cycle signatures were more highly expressed in BM2. A multivariate model of PFS incorporating BM subtype plus immune and cell-cycle signatures revealed that BM subtype encompasses the majority of the effect.

CONCLUSIONS

BM subtype is significantly associated with the outcome of combination dabrafenib, trametinib, and panitumumab therapy and may serve as a standalone predictive biomarker beyond mutational status. Our findings support a more nuanced approach to targeted therapeutic decisions that incorporates assessment of transcriptional context.

Combined BRAF, EGFR, and MEK Inhibition in Patients with BRAFV600E-Mutant Colorectal Cancer

Although BRAF inhibitor monotherapy yields response rates >50% in BRAFV600-mutant melanoma, only approximately 5% of patients with BRAFV600E colorectal cancer respond. Preclinical studies suggest that the lack of efficacy in BRAFV600E colorectal cancer is due to adaptive feedback reactivation of MAPK signaling, often mediated by EGFR. This clinical trial evaluated BRAF and EGFR inhibition with dabrafenib (D) + panitumumab (P) ± MEK inhibition with trametinib (T) to achieve greater MAPK suppression and improved efficacy in 142 patients with BRAFV600E colorectal cancer. Confirmed response rates for D+P, D+T+P, and T+P were 10%, 21%, and 0%, respectively. Pharmacodynamic analysis of paired pretreatment and on-treatment biopsies found that efficacy of D+T+P correlated with increased MAPK suppression. Serial cell-free DNA analysis revealed additional correlates of response and emergence of KRAS and NRAS mutations on disease progression. Thus, targeting adaptive feedback pathways in BRAFV600E colorectal cancer can improve efficacy, but MAPK reactivation remains an important primary and acquired resistance mechanism.Significance: This trial demonstrates that combined BRAF + EGFR + MEK inhibition is tolerable, with promising activity in patients with BRAFV600E colorectal cancer. Our findings highlight the MAPK pathway as a critical target in BRAFV600E colorectal cancer and the need to optimize strategies inhibiting this pathway to overcome both primary and acquired resistance. Cancer Discov; 8(4); 428-43. ©2018 AACR.See related commentary by Janku, p. 389See related article by Hazar-Rethinam et al., p. 417This article is highlighted in the In This Issue feature, p. 371.

Dabrafenib and Trametinib Treatment in Patients With Locally Advanced or Metastatic BRAF V600-Mutant Anaplastic Thyroid Cancer

Purpose We report the efficacy and safety of dabrafenib (BRAF inhibitor) and trametinib (MEK inhibitor) combination therapy in BRAF V600E-mutated anaplastic thyroid cancer, a rare, aggressive, and highly lethal malignancy with poor patient outcomes and no systemic therapies with clinical benefit. Methods In this phase II, open-label trial, patients with predefined BRAF V600E-mutated malignancies received dabrafenib 150 mg twice daily and trametinib 2 mg once daily until unacceptable toxicity, disease progression, or death. The primary end point was investigator-assessed overall response rate. Secondary end points included duration of response, progression-free survival, overall survival, and safety. Results Sixteen patients with BRAF V600E-mutated anaplastic thyroid cancer were evaluable (median follow-up, 47 weeks; range, 4 to 120 weeks). All patients had received prior radiation treatment and/or surgery, and six had received prior systemic therapy. The confirmed overall response rate was 69% (11 of 16; 95% CI, 41% to 89%), with seven ongoing responses. Median duration of response, progression-free survival, and overall survival were not reached as a result of a lack of events, with 12-month estimates of 90%, 79%, and 80%, respectively. The safety population was composed of 100 patients who were enrolled with seven rare tumor histologies. Common adverse events were fatigue (38%), pyrexia (37%), and nausea (35%). No new safety signals were detected. Conclusion Dabrafenib plus trametinib is the first regimen demonstrated to have robust clinical activity in BRAF V600E-mutated anaplastic thyroid cancer and was well tolerated. These findings represent a meaningful therapeutic advance for this orphan disease.

Understanding the mechanisms of action of antiangiogenic agents in metastatic colorectal cancer: a clinician's perspective

Multiple clinical trials using bevacizumab, ziv-aflibercept, and regorafenib have recently demonstrated efficacy for patients with metastatic colorectal cancer. While the net clinical benefit of each of these therapies in the second-line and refractory disease setting appears to be similar, important distinctions exist between the agents at the pharmacodynamic, tumor microenvironment, and clinical levels. The purpose of this review is to survey the preclinical evidence regarding the mechanisms of action of these novel antiangiogenic agents and provide an overview of their respective clinical activity, while highlighting distinctions between therapies. Fundamental understanding of these distinctions may aid in clinical decisions and choice of antiangiogenic therapies.

Phase I study of capecitabine, oxaliplatin, bevacizumab, and everolimus in advanced solid tumors

PURPOSE

To define maximum tolerated dose (MTD), toxicities, and pharmacodynamics of capecitabine, oxaliplatin, bevacizumab, and everolimus in advanced solid tumor patients.

DESIGN

This was a standard "3 + 3" dose-escalation trial. All subjects received bevacizumab 7.5 mg/kg on day 1 of each cycle. Doses for capecitabine, oxaliplatin and everolimus were modified per dose limiting toxicity (DLT). Baseline and on-treatment plasma biomarkers were analyzed. Archived tumor mRNA levels were evaluated for NRP1, NRP2 and VEGF-A isoforms.

RESULTS

Twenty-nine patients were evaluable for toxicity and 30 for efficacy. Two DLTs were observed in cohort 1 and one DLT each was observed in cohort -1 and -1b. Grade ≥3 toxicities included neutropenia, hypertension, perforation/fistula/hemorrhage, hypertriglyceridemia, diarrhea, and thromboembolism. Twelve subjects experienced partial response (PR); 12 had stable disease as best response. Three of seven chemorefractory metastatic colorectal cancer (mCRC) subjects experienced PR; 8 of 15 chemonaive mCRC subjects experienced PR. Plasma TβRIII and IL-6 increased on treatment but without correlation to outcome. Increased VEGF165 levels significantly correlated with longer progression free survival.

CONCLUSIONS

Everolimus with full dose capecitabine, oxaliplatin, and bevacizumab had unacceptable toxicity. MTD was: everolimus 5 mg daily; capecitabine 680 mg/m(2) BID days 1-14; oxaliplatin 100 mg/m(2) and bevacizumab 7.5 mg/kg, day 1. Activity was noted in mCRC.

Differential effects of arsenic trioxide on chemosensitization in human hepatic tumor and stellate cell lines

BACKGROUND

Crosstalk between malignant hepatocytes and the surrounding peritumoral stroma is a key modulator of hepatocarcinogenesis and therapeutic resistance. To examine the chemotherapy resistance of these two cellular compartments in vitro, we evaluated a well-established hepatic tumor cell line, HepG2, and an adult hepatic stellate cell line, LX2. The aim was to compare the chemosensitization potential of arsenic trioxide (ATO) in combination with sorafenib or fluorouracil (5-FU), in both hepatic tumor cells and stromal cells.

METHODS

Cytotoxicity of ATO, 5-FU, and sorafenib, alone and in combination against HepG2 cells and LX2 cells was measured by an automated high throughput cell-based proliferation assay. Changes in survival and apoptotic signaling pathways were analyzed by flow cytometry and western blot. Gene expression of the 5-FU metabolic enzyme, thymidylate synthase, was analyzed by real time PCR.

RESULTS

Both HepG2 and LX2 cell lines were susceptible to single agent sorafenib and ATO at 24 hr (ATO IC(50): 5.3 μM in LX2; 32.7 μM in HepG2; Sorafenib IC(50): 11.8 μM in LX2; 9.9 μM in HepG2). In contrast, 5-FU cytotoxicity required higher concentrations and prolonged (48-72 hr) drug exposure. Concurrent ATO and 5-FU treatment of HepG2 cells was synergistic, leading to increased cytotoxicity due in part to modulation of thymidylate synthase levels by ATO. Concurrent ATO and sorafenib treatment showed a trend towards increased HepG2 cytotoxicity, possibly due to a significant decrease in MAPK activation in comparison to treatment with ATO alone.

CONCLUSIONS

ATO differentially sensitizes hepatic tumor cells and adult hepatic stellate cells to 5-FU and sorafenib. Given the importance of both of these cell types in hepatocarcinogenesis, these data have implications for the rational development of anti-cancer therapy combinations for the treatment of hepatocellular carcinoma (HCC).

Histoplasmosis and penicilliosis among HIV-infected Thai patients: a retrospective review

Histoplasmosis and penicilliosis are fungal infections with similar clinical presentation and laboratory findings that were reported mainly in the era prior to highly active antiretroviral therapy. We conducted a retrospective review at two hospitals in Central Thailand of the medical records of HIV-positive patients with microbiologic evidence of histoplasmosis or penicilliosis between January 2003 to September 2007 when antiretrovirals became widely available in Thailand. Fifty patients met inclusion criteria; 36 had histoplasmosis, and 14 had penicilliosis. Symptoms and laboratory findings on presentation were similar between the two infections except for a greater incidence of tachypnea and neutropenia among patients with histoplasmosis (both p < 0.05). For histoplasmosis, blood culture had a significantly lower yield for detecting infection compared to tissue microscopic examination highlighting the importance of obtaining tissue for diagnosis (p < 0.05).

Gastrointestinal symptoms in cancer patients with advanced disease: new methodologies, insights, and a proposed approach

PURPOSE OF REVIEW

This review summarizes recent developments in the management of gastrointestinal symptoms experienced by cancer patients and provides a framework for education, assessment and monitoring, and treatment.

RECENT FINDINGS

Although many viable treatment options exist, gastrointestinal symptoms - particularly nausea and vomiting, constipation, and diarrhea - continue to challenge both patients and clinicians. Current clinical guidelines now recommend that patients treated with moderate emetic risk chemotherapy regimens be preferentially treated with the 5-hydroxytryptamine type 3 (5-HT3) receptor antagonist, palonosetron, in combination with dexamethasone. A large randomized trial has also recently validated that single-dose fosaprepitant is equivalent to the standard 3-day, aprepitant regimen. New medications, such as skin patch delivery of granisetron for nausea or methylnaltrexone for constipation, show promise in both the management of symptoms and as preventive agents. The integration of complementary and alternative therapies, such as relaxation techniques, ginger, and electroacupuncture may also assist with symptom relief. Accurate assessment is essential, but often problematic, especially as the patient's experience of gastrointestinal distress is often disproportionate with objective measures. New methodologies that harness technology to collect patient-reported outcomes may improve the accuracy of assessment, provide a better picture of the patient's experience of gastrointestinal symptoms, and deliver a means to simultaneously monitor symptoms, educate patients, and collect longitudinal data.

SUMMARY

Palliative management of gastrointestinal symptoms in advanced cancer patients requires a multipronged approach that entails effective assessment, judicious use of latest evidence-based approaches, and monitoring that incorporates both clinical measures and patient-reported outcomes. When combined with refinements in the overall clinical approach to symptom management, standardized instruments that streamline data collection and enable data warehousing will support better symptom management.

Hedgehog signaling antagonist promotes regression of both liver fibrosis and hepatocellular carcinoma in a murine model of primary liver cancer

OBJECTIVE

Chronic fibrosing liver injury is a major risk factor for hepatocarcinogenesis in humans. Mice with targeted deletion of Mdr2 (the murine ortholog of MDR3) develop chronic fibrosing liver injury. Hepatocellular carcinoma (HCC) emerges spontaneously in such mice by 50-60 weeks of age, providing a model of fibrosis-associated hepatocarcinogenesis. We used Mdr2(-/-) mice to investigate the hypothesis that activation of the hedgehog (Hh) signaling pathway promotes development of both liver fibrosis and HCC.

METHODS

Hepatic injury and fibrosis, Hh pathway activation, and liver progenitor populations were compared in Mdr2(-/-) mice and age-matched wild type controls. A dose finding experiment with the Hh signaling antagonist GDC-0449 was performed to optimize Hh pathway inhibition. Mice were then treated with GDC-0449 or vehicle for 9 days, and effects on liver fibrosis and tumor burden were assessed by immunohistochemistry, qRT-PCR, Western blot, and magnetic resonance imaging.

RESULTS

Unlike controls, Mdr2(-/-) mice consistently expressed Hh ligands and progressively accumulated Hh-responsive liver myofibroblasts and progenitors with age. Treatment of aged Mdr2-deficient mice with GDC-0449 significantly inhibited hepatic Hh activity, decreased liver myofibroblasts and progenitors, reduced liver fibrosis, promoted regression of intra-hepatic HCCs, and decreased the number of metastatic HCC without increasing mortality.

CONCLUSIONS

Hh pathway activation promotes liver fibrosis and hepatocarcinogenesis, and inhibiting Hh signaling safely reverses both processes even when fibrosis and HCC are advanced.

Increased production of sonic hedgehog by ballooned hepatocytes

Ballooned hepatocytes distinguish non-alcoholic steatohepatitis (NASH) from steatosis. Such cells contain dilated endoplasmic reticulum and ubiquitin aggregates, characteristics of endoplasmic reticulum stress. Hepatocyte ballooning increases the risk for fibrosis in NASH, suggesting that ballooned hepatocytes release pro-fibrogenic factors. Hedgehog ligands function as pro-fibrogenic factors in liver diseases, but mechanisms for hedgehog ligand production remain poorly understood. We evaluated the hypothesis that endoplasmic reticulum stress induces hepatocyte production of hedgehog ligands that provide paracrine pro-fibrogenic signals to neighbouring cells. In livers from NASH patients, keratin 8/18 and ubiquitin staining demonstrated enlarged, keratin 8/18-negative/ubiquitin-positive hepatocytes (ballooned hepatocytes) that were positive for Sonic hedgehog. In order to model endoplasmic reticulum stress in vitro, primary mouse hepatocytes were treated with tunicamycin. Compared to vehicle, tunicamycin significantly increased Sonic hedgehog and Indian hedgehog expression. Furthermore, conditioned medium from tunicamycin-treated hepatocytes increased Gli-luciferase reporter activity 14-fold more than conditioned medium from vehicle-treated hepatocytes. Cyclopamine (hedgehog signalling inhibitor) abrogated the effect of conditioned medium from tunicamycin-treated hepatocytes, verifying that soluble hepatocyte-derived factors activate hedgehog signalling. Ballooned hepatocytes in NASH patients did not express the hedgehog target gene, Gli2, α-smooth muscle actin or vimentin, but were surrounded by Gli2-positive stromal cells expressing these myofibroblast markers. Trichrome staining demonstrated the accumulation of ballooned hepatocytes in areas of matrix deposition, and numbers of Sonic hedgehog-positive hepatocytes correlated with the degree of ballooning and fibrosis stage. Hepatocytes undergoing endoplasmic reticiulum stress generate hedgehog ligands which act as paracrine pro-fibrogenic factors for hedgehog-responsive stromal cells. These results help to explain why fibrosis stage correlates with hepatocyte ballooning in NASH.

Malignant peripheral nerve sheath tumors with high and low Ras-GTP are permissive for oncolytic herpes simplex virus mutants

BACKGROUND

Malignant peripheral nerve sheath tumors (MPNSTs) occur most frequently in patients with neurofibromatosis type 1 and are often fatal. Current therapy relies upon radical surgical resection, which often fails to completely remove the tumor. To address the need for novel treatment approaches for this disease, we sought to determine if human MPNST-derived cell lines are sensitive to oncolytic Herpes simplex virus (oHSV) infection. Activation of the Ras pathway and its inhibitory effects on protein kinase R (PKR) activation have been shown to dictate cellular permissivity to oHSV mutants. Because NF-1-associated MPNSTs possess inherent hyperactive Ras, we hypothesized these tumors would be ideal therapeutic targets for oHSVs.

PROCEDURE

Human MPNST-derived cell lines were examined for sensitivity to oHSV-mediated gene transduction, virus replication, cytotoxicity, and apoptosis. These parameters were correlated with PKR activation following oHSV infection and compared with normal human Schwann cells (NHSCs) without hyperactive Ras.

RESULTS

MPNST-derived cell lines were efficiently transduced, supported virus replication and were killed by the oncolytic HSV mutants, including sporadic MPNSTs without hyperactive Ras. In contrast to the highly sensitive MPNST cell lines, NHSCs did not support mutant virus replication.

CONCLUSIONS

MPNSTs are susceptible to lysis by oncolytic HSV mutants, regardless of Ras status. Tumor-selective virus replication in MPNST cells appears to be mediated by both cellular expression of ribonucleotide reductase and prevention of eIF2alpha phosphorylation. Virus-induced cytotoxicity of MPNST cell lines was caused by both direct lysis and apoptosis. Our data suggest the use of oncolytic HSV mutants may represent a novel treatment approach for patients with MPNSTs.

Large-scale molecular comparison of human schwann cells to malignant peripheral nerve sheath tumor cell lines and tissues

Malignant peripheral nerve sheath tumors (MPNST) are highly invasive soft tissue sarcomas that arise within the peripheral nerve and frequently metastasize. To identify molecular events contributing to malignant transformation in peripheral nerve, we compared eight cell lines derived from MPNSTs and seven normal human Schwann cell samples. We found that MPNST lines are heterogeneous in their in vitro growth rates and exhibit diverse alterations in expression of pRb, p53, p14(Arf), and p16(INK4a) proteins. All MPNST cell lines express the epidermal growth factor receptor and lack S100beta protein. Global gene expression profiling using Affymetrix oligonucleotide microarrays identified a 159-gene molecular signature distinguishing MPNST cell lines from normal Schwann cells, which was validated in Affymetrix microarray data generated from 45 primary MPNSTs. Expression of Schwann cell differentiation markers (SOX10, CNP, PMP22, and NGFR) was down-regulated in MPNSTs whereas neural crest stem cell markers, SOX9 and TWIST1, were overexpressed in MPNSTs. Previous studies have implicated TWIST1 in apoptosis inhibition, resistance to chemotherapy, and metastasis. Reducing TWIST1 expression in MPNST cells using small interfering RNA did not affect apoptosis or chemoresistance but inhibited cell chemotaxis. Our results highlight the use of gene expression profiling in identifying genes and molecular pathways that are potential biomarkers and/or therapeutic targets for treatment of MPNST and support the use of the MPNST cell lines as a primary analytic tool.

Role of TC21/R-Ras2 in enhanced migration of neurofibromin-deficient Schwann cells

The neurofibromatosis type 1 tumor suppressor protein neurofibromin, is a GTPase activating protein for H-, N-, K-, R-Ras and TC21/R-Ras2 proteins. We demonstrate that Schwann cells derived from Nf1-null mice have enhanced chemokinetic and chemotactic migration in comparison to wild-type controls. Surprisingly, this migratory phenotype is not inhibited by a farnesyltransferase inhibitor or dominant-negative (dn) (N17)H-Ras (which inhibits H-, N-, and K-Ras activation). We postulated that increased activity of R-Ras and/or TC21/R-Ras2, due to loss of Nf1, contributes to increased migration. Mouse Schwann cells (MSCs) express R-Ras and TC21/R-Ras2 and their specific guanine exchange factors, C3G and AND-34. Infection of Nf1-null MSCs with a dn(43N)R-Ras adenovirus (to inhibit both R-Ras and TC21/R-Ras2 activation) decreases migration by approximately 50%. Conversely, expression of activated (72L)TC21/R-Ras2, but not activated (38V)R-Ras, increases migration, suggesting a role of TC21/R-Ras2 activation in the migration of neurofibromin-deficient Schwann cells. TC21/R-Ras2 preferentially couples to the phosphatidylinositol 3-kinase (PI3-kinase) and MAP kinase pathways. Treatment with a PI3-kinase or MAP kinase inhibitor reduces Nf1-null Schwann cell migration, implicating these TC21 effectors in Schwann cell migration. These data reveal a key role for neurofibromin regulation of TC21/R-Ras2 in Schwann cells, a cell type critical to NF1 tumor pathogenesis.

Neuronal alpha-bungarotoxin receptors differ structurally from other nicotinic acetylcholine receptors

We have characterized the alpha-bungarotoxin receptors (BgtRs) found on the cell surface of undifferentiated pheochromocytoma (PC12) cells. The PC12 cells express a homogeneous population of alpha7-containing receptors that bind alpha-Bgt with high affinity (Kd = 94 pM). The BgtRs mediate most of the response elicited by nicotine, because the BgtR-specific antagonists methyllycaconitine and alpha-Bgt block approximately 90% of the whole-cell current. The binding of nicotinic agonists to cell-surface BgtRs was highly cooperative with four different agonists showing Hill coefficients in the range of 2.3-2.4. A similar agonist binding cooperativity was observed for BgtR homomers formed from chimeric alpha7/5HT3 subunits expressed in tsA 201 cells. Two classes of agonist binding sites, in the ratio of 4:1 for PC12 cell BgtRs and 3:1 for alpha7/5HT3 BgtRs, were revealed by bromoacetylcholine alkylation of the reduced sites on both PC12 BgtRs and alpha7/5HT3 BgtRs. We conclude from this data that PC12 BgtRs and alpha7/5HT3 homomers contain at least three distinguishable agonist binding sites and thus are different from other nicotinic receptors.