Napabucasin (BBI 608), a potent chemoradiosensitizer in rectal cancer

BACKGROUND

The induction of reactive oxygen species (ROS) represents a viable strategy for enhancing the activity of radiotherapy. The authors hypothesized that napabucasin would increase ROS via its ability to inhibit NAD(P)H:quinone oxidoreductase 1 and potentiate the response to chemoradiotherapy in rectal cancer via distinct mechanisms.

METHOD

Proliferation studies, colony formation assays, and ROS levels were measured in HCT116 and HT29 cell lines treated with napabucasin, chemoradiation, or their combination. DNA damage (pγH2AX), activation of STAT, and downstream angiogenesis were evaluated in both untreated and treated cell lines. Finally, the effects of napabucasin, chemoradiotherapy, and their combination were assessed in vivo with subcutaneous mouse xenograft models.

RESULTS

Napabucasin significantly potentiated the growth inhibition of chemoradiation in both cell lines. Napabucasin increased ROS generation. Inhibition of ROS by N-acetylcysteine decreased the growth inhibitory effect of napabucasin alone and in combination with chemoradiotherapy. Napabucasin significantly increased pγH2AX in comparison with chemoradiotherapy alone. Napabucasin reduced the levels of pSTAT3 and VEGF and inhibited angiogenesis through an ROS-mediated effect. Napabucasin significantly potentiated the inhibition of growth and blood vessel formation by chemoradiotherapy in mouse xenografts.

CONCLUSION

Napabucasin is a radiosensitizer with a novel mechanism of action: increasing ROS production and inhibiting angiogenesis. Clinical trials testing the addition of napabucasin to chemoradiotherapy in rectal cancer are needed.

Feasibility of a collaborative palliative and oncology care intervention to improve symptoms and coping during head and neck chemoradiation

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Background: Patients receiving curative chemoradiation treatment (CRT) for head and neck cancer (HNC) undergo one of the most intensive treatments in oncology, resulting in immense physical and psychological symptoms. Integrated palliative care can improve symptoms and coping in patients with advanced cancer, but has not been evaluated in patients with curable solid tumors. Thus, we are conducting the first pilot study of a collaborative palliative and oncology care intervention among patients receiving CRT to assess feasibility and acceptability. Methods: Eligible participants include newly diagnosed HNC patients starting curative-intent CRT. The intervention entails weekly in-person palliative care (PC) visits integrated with standard oncology care during CRT, followed by 4 weekly phone calls after CRT ends. The PC visits are conducted primarily by a PC RN, with a supervising MD or NP available. Visits focus on coping and managing prominent symptoms during CRT. PC clinicians also receive a weekly patient-reported symptom assessment. Acceptability of the intervention is assessed at 1 month post CRT. The primary outcome is feasibility, defined as a >50% enrollment rate with >70% of participants attending at least half of the PC visits. Planned accrual is 20 patients. Results: We have enrolled 88% (14/16) of eligible patients to date. 11/14 (79%) have p16+ disease. All 14 have completed CRT and are evaluable for feasibility. Participants attended 98% (94/96) of all possible PC visits and completed 99% (95/96) of weekly symptom assessments. PC clinicians spent an average of 35.5 minutes (SD 15.1) per visit with participants. Among the 10 participants who completed the intervention and are evaluable for acceptability, 100% found the intervention “very helpful” and would “definitely recommend” it to others undergoing CRT. Conclusions: An integrated PC intervention to improve symptoms and coping during CRT for HNC is both feasible and acceptable with a high enrollment rate, excellent intervention compliance, and high patient satisfaction. Future studies will evaluate the effects of the integrated intervention on patient-reported outcomes and health care utilization. Clinical trial information: NCT03760471.

Comprehensive analysis of radiographic, clinical, and inflammatory markers demonstrating changes in lean muscle correlate with outcome in patients (pts) with metastatic pancreatic adenocarcinoma (mPDAC) who undergo taxane-based chemotherapy (CT)

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Background: MPDAC is associated with a poor prognosis. The mechanisms of carcinogenesis are complex; involve multiple signaling pathways and inflammatory cytokines that may promote cachexia, a major cause of morbidity and mortality in mPDAC. The purpose of this study is to understand factors related to skeletal muscle changes, and its effect on outcomes in pts with mPDAC. Methods: Pt and clinical data were obtained from a recent prospective clinical trial in mPDAC where all pts received first-line taxane-based CT. We examined changes in modified Glasgow prognostic score, neutrophil lymphocyte ratio, a 32-cytokine panel, weight, and skeletal muscle area (SMA), determined by validated methodology with computed tomography, at baseline and cycle 3. We defined > 6cm2 in SMA, correlating to 1kg of skeletal muscle gain (SMG), as significant. Univariate and multivariate Cox regression models were used to determine the association between laboratory, radiographic and clinical findings with progression free survival (PFS) and overall survival (OS). Results: 66 evaluable pts were included. Independent of clinical response, an OS advantage was seen in pts who experienced significant SMG (p = 0.023) and in patients with nominal SMG (p = 0.012). A numerical benefit in PFS was observed with SMG. Decreases in IFN-a (p = 0.024), IFN-g (p = 0.001) and IL-6 (p = 0.042) were inversely associated with SMG. A comprehensive analysis incorporating all relevant laboratory, radiographic and clinical assessments demonstrated a 4.62-month OS advantage in pts with favorable characteristics vs. those with poor prognostic factors (11.47 versus 6.84 mos., p = 0.0029). Conclusions: SMG, or the reversal of cachexia confers an OS advantage in pts with mPDAC treated with taxane-based CT regardless of clinical response. A comprehensive assessment of muscle change is a precise measurement that can identify pts at greatest risk for muscle loss, which could predict for trmt response and pt outcomes. This merits further investigation as a tool and in trials directed at reversing the process of cachexia.

Leptin, BMI, and a Metabolic Gene Expression Signature Associated with Clinical Outcome to VEGF Inhibition in Colorectal Cancer

VEGF (vascular endothelial growth factor) signaling inhibitors are widely used in different cancer types; however, patient selection remains a challenge. Analyses of samples from a phase III clinical trial in metastatic colorectal cancer testing chemotherapy versus chemotherapy with the small molecule VEGF receptors inhibitor cediranib identified circulating leptin levels, BMI, and a tumor metabolic and angiogenic gene expression signature associated with improved clinical outcome in patients treated with cediranib. Patients with a glycolytic and hypoxic/angiogenic profile were associated with increased benefit from cediranib, whereas patients with a high lipogenic, oxidative phosphorylation and serine biosynthesis signature did not gain benefit. These findings translated to pre-clinical tumor xenograft models where the same metabolic gene expression profiles were associated with in vivo sensitivity to cediranib as monotherapy. These findings suggest a link between patient physiology, tumor biology, and response to antiangiogenics, which may guide patient selection for VEGF therapy in the future.

Abstract 4278: Soy isoflavones and their metabolites modulate IL-12-induced NK cell IFN-γ production

Soybeans and foods derived from them are a rich source of phytochemcials that have gained attention due to their ability to affect obesity, metabolism, cancer, and inflammation. Soy isoflavones (genistein and daidzein) have also been shown to be differentially metabolized between individuals. This is presumably due to differences in gut microbiota, and can lead to production of terminal isoflavone metabolites such as O-desmethylangolensin (ODMA) and equol. In a prior phase-I clinical study conducted by our group, patients with prostate cancer received a novel soy-enriched bread product. Analysis of blood and urine following soy intervention revealed that men clustered into distinct groups based on their ability to metabolize daidizein into either ODMA or equol. Reduced pro-inflammatory cytokines and percentages of Tregs and MDSC were also observed in the blood of patients after 8 weeks of soy bread intervention as compared to baseline. Given these differences, we hypothesized that individual isoflavones and metabolites would have unique immunomodulatory effects upon human natural killer (NK) cell function. Although a limited number of prior studies have evaluated how soy isoflavones or their metabolites modulate inflammation and different immune subsets (monocytes, macrophages, DCs), their role in NK cell biology remains poorly defined. Understanding the role of soy isoflavones and their metabolites in regulating NK cell activity is critical due to NK cells’ importance in the anti-tumor response and immunosurveillance. We found that the soy isoflavones and their metabolites did not affect the viability of healthy donor PBMC (n = 3) at concentrations as high as 25μM. However, pre-treatment of healthy donor PBMC (n = 3) with genistein (mean 7.1 ng/ml ±1.3) or equol (mean 6.7 ng/ml ±1.8) for 4 hours and then stimulated with IL-12/18 for 72 hours decreased IFN-γ production compared to unstimulated controls (mean 26.7 ng/ml ±16.1). In contrast, daidzein and ODMA had no effect. We next utilized intracellular flow cytometry to determine the cellular subset(s) that were modulated by soy isoflavones or their metabolites. These data revealed that only genistein and equol decreased the percentage of IL-12/18 induced IFN-γ producing NK cells (CD56+CD3-) by 30% and 53%, respectively. There was no observed difference in other IFN-γ producing immune subsets (T and NKT cells) when cultured with the soy isoflavones or metabolites. Furthermore, we found soy isoflavones and metabolites altered in vitro cytotoxicity of human IL-12 stimulated NK cells. Ongoing studies in our laboratory are elucidating the precise signaling pathways downstream of IL-12 in human NK cells that are modulated in response to soy isoflavones and their bioactive metabolites. This study provides critical insight regarding the impact of dietary soy on NK cell mediated responses potentially informing the use of soy during chemopreventive or immune based therapies.

Citation Format: Thomas A. Mace, Samantha King, Matthew Farren, Elizabeth McMichael, Steven Scoville, William E. Carson, Gregory Young, Jennifer Thomas-Ahner, Kenneth M. Riedl, Steven Schwartz, Steven K. Clinton, Gregory Lesinski. Soy isoflavones and their metabolites modulate IL-12-induced NK cell IFN-γ production. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4278. doi:10.1158/1538-7445.AM2015-4278

Abstract 4695: Dual targeting of MEK and PI3K pathways can act via tumor-intrinsic mechanisms to overcome resistance and tumor-extrinsic mechanisms to modulate immunity and limit cancer cachexia

Prior studies by our group have shown that single-agent MEK inhibitors have clinical activity in cholangiocarcinoma (CC), including objective responses. Yet no relationship was found between clinical benefit, and oncogenic driver mutations such as KRAS or BRAF. Strategies to expand upon MEKi have focused on combinations with agents targeting resistance, such as the PI3K/Akt pathway. CC patients treated with MEKi also had reduced pro-inflammatory cytokines and weight gain with restoration of muscle mass. These findings are clinically significant, and led us to hypothesize that MEKi act via tumor-extrinsic mechanisms to modulate immunity and limit cancer cachexia, while overcoming tumor-intrinsic resistance. We used the colon-26 adenocarcinoma model to evaluate the effect of single and combined treatment with MEK162 (30mg/kg) and buparlisib (25mg/kg) on muscle wasting, tumor growth, and immune modulation. This murine model depends on interleukin-6 (IL-6) and recapitulates the cancer cachexia syndrome. Single agent MEK162 inhibited growth initially, but after 14 days, tumor volume was comparable between MEKi and vehicle treated mice, possibly from acquired MEK162 resistance. Despite these data, reduced serum IL-6 and splenic Gr1+CD11b+ cells were evident compared to control mice (mean = 358 pg/mL to 43 pg/mL, and 13.8% to 8.4%, respectively), while body weight from MEK162 treated mice was spared (mean = 24.0g to 20.5g in control mice). In addition, markers of muscle catabolism, including the E3 ubiquitin ligases Atrogin-1 (from 1 to 0.043 in combo) and MuRF1 (from 1 to 0.03 in combo), and the autophagy gene, Bnip3, were all reduced in tibialis anterior muscles from tumor-bearing mice treated with MEK162. Similar to our clinical data, these results suggest MEK162 modulates immune biomarkers, and acts as an anti-cachexia agent. Since cross talk between MAPK and PI3K/AKT pathways promotes resistance to monotherapy, we next investigated the effects of MEK162 combined with buparlisib in the colon-26 model. As before, single agent MEK162 had a modest growth inhibitory effect, yet rescued body weight. Consistent with in vitro studies, single agent buparlisib was cytostatic, but not as effective as MEK162 in rescuing weight loss. However, dual treatment with MEK162 + buparlisib significantly inhibited tumor growth. This combination also significantly reduced splenic MDSC (mean = 37% to 9% in control mice) and increased CD4+ and CD8+ (mean = 24% to 6%, and 7.7% to 2%, respectively) T cells. These results suggest that dual inhibition of MEK and PI3K has efficacy, while MEKi may have under-appreciated tumor-extrinsic mechanisms of activity that can be leveraged to benefit patients with advanced malignancy. This treatment combination will be evaluated in CC patients in the setting of a Phase II clinical trial.

Citation Format: Jennifer Yang, Erin Talbert, Omar Elnaggar, Priyani Rajasekera, Thomas Mace, Matthew Farren, Zheng Che, Benjamin Swanson, Gregory Young, Ericka Haverick, Cynthia Timmers, Mark Bloomston, Tanios Bekaii-Saab, Denis Guttridge, Gregory Lesinski. Dual targeting of MEK and PI3K pathways can act via tumor-intrinsic mechanisms to overcome resistance and tumor-extrinsic mechanisms to modulate immunity and limit cancer cachexia. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4695. doi:10.1158/1538-7445.AM2015-4695

Abstract 2656: Combined inhibition of MEK and PI3K elicits anti-tumor activity in human cholangiocarcinoma

Cholangiocarcinoma (CC) responds poorly to chemo- and immunotherapy and is nearly always fatal within one year. In recent years we have gained important insight into the signaling pathways that drive this cancer. These cancers are characterized by deregulated mitogen-activated protein kinase (MAPK), PI3 kinase/Akt and a dependence on the IL-6 axis of signal transduction. Importantly, we previously reported clinical responses for CC patients receiving single agent MEK inhibitors, indicating these agents have activity in this disease. We hypothesized that dual targeting of these pathways in CC using MEK162 and buparlisib would lead to potent antitumor and immunomodulatory activity, possibly circumventing resistance to single agent MEK162. In a panel of n = 7 human CC cell lines with diverse genetic profiles, constitutive phosphorylation of ERK (7/7) and Akt (2/7) was observed. Human CC cell lines displayed variable sensitivity to the growth inhibitory and pro-apoptotic effects of single agent MEK162 or buparlisib. CC cell lines with basal AKT phosphorylation (WITT, Mz-Cha-1) showed greater sensitivity to growth inhibition by buparlisib (IC50 10-20 μM), as compared to CC lines lacking pAKT (HuCCT1, HuH28, IC50 > 20μM). Immunoblot analysis confirmed decreased phosphorylated ERK (pERK) in the HuCCT1 and SNU-478 CC cell lines following treatment with MEK162. Culture supernatants from four separate human CC cell lines displayed significant reductions in IL-6, VEGF, and GM CSF in a concentration-dependent manner after treatment with MEK162. Immunomodulatory effects of MEK162 were also evident, independent of its tumor-intrinsic effects upon CC cell lines. Namely, it significantly reduced IL 6/GM-CSF driven MDSC differentiation (HLA-DRlo CD11b+ CD33+) from healthy normal donor PBMC in vitro. These observations were not due to cytotoxic activity as treatment with MEK162 for 72 hours did not reduce viability of bulk human PBMCs. Finally, to evaluate the effect of this treatment combination, in vivo studies were conducted in athymic mice bearing Mz-Cha1 or SNU-478 xenografts. Tumor bearing mice received daily oral administration of MEK162 (30 mg/kg), buparlisib (25 mg/kg), or both agents combined. Vehicle treated animals served as negative controls. Inhibition of tumor growth was observed following administration of single agent MEK162 or buparlisib as compared to control animals. This effect was further enhanced in the combination treated animals. Body weight of animals indicated this regimen was well-tolerated. Together, these data suggest that dual PI3K and MEK inhibition can target CC with varying genotypes and represents a promising therapeutic regimen with potential for direct antitumor activity and immunomodulation in CC.

Citation Format: Jennifer Yang, Omar Elnaggar, Thomas Mace, Matthew Farren, Gregory Young, Patrice Lee, Kaitlin Keenan, Zheng Che, Jacob Kaufman, Denis Guttridge, David Carbone, Cynthia Timmers, Tanios Bekaii-Saab, Gregory Lesinski. Combined inhibition of MEK and PI3K elicits anti-tumor activity in human cholangiocarcinoma. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2656. doi:10.1158/1538-7445.AM2015-2656

Maternal Obesity and Neck Circumference

Obese women are more likely to require general anaesthesia for an obstetric intervention than non-obese. Difficult tracheal intubation and oxygen desaturation is more common in pregnancy. Failed tracheal intubation has been associated with an increase in neck circumference (NC). We studied the relationship between maternal obesity and NC as pregnancy advanced in women attending a standard antenatal clinic. Of the 96 women recruited, 13.5% were obese. The mean NC was 36.8cm (SD 1.9) in the obese women compared with 31.5cm (SD 1.6) in women with a normal BMI (p < 0.001) at 18-22 weeks gestation. In the obese women it increased on average by 1.5cm by 36-40 weeks compared with an increase of 1.6 cm in women with a normal BMI. The antenatal measurement of NC is a simple, inexpensive tool that is potentially useful for screening obese women who may benefit from an antenatal anaesthetic assessment.

Mild cold stress resulting from standard housing conditions for laboratory mice influences baseline dendritic cell properties (TUM2P.896)

The ability of dendritic cells (DC) to stimulate and regulate T cells is critical for effective anti-tumor immunity. Therefore, it is important to recognize any inherent factors which may influence DC function under experimental conditions, especially in laboratory mice which are commonly used to model anti-tumor immunity. Recent data shows that CD8+ T cell frequency within the tumor microenvironment and anti-tumor function is dependent upon the ambient temperature used to house laboratory mice. As DC function is crucial for CD8+ T cell activation, we hypothesized that DC function is also dependent upon housing temperature. We observed increased numbers of splenic DCs (CD11c+ ) in tumor-bearing mice at housed at standard temperature (ST; 22°C) vs. mice housed at a thermoneutral temperature (TT; 30°C) which alleviates the mild cold stress experienced at ST. Despite increased frequency, DCs from mice at ST primarily display immature phenotypes (MHC II+CD86- ), likely rendering them tolerogenic and unable to activate T cells. Further, splenocytes from tumor-bearing mice at ST were unable to induce T cell proliferation following tumor inoculation while DCs from mice at TT elicited T cell activation. These findings likely contribute to faster tumor growth observed in mice at ST vs. TT. This data strongly suggests that the housing temperature can affect fundamental properties of DC function which in turn influence the ability of DCs to regulate the anti-tumor immune response.

Tumor stromal architecture can define the intrinsic tumor response to VEGF-targeted therapy

PURPOSE

The aim of the study was to investigate the vascular and stromal architecture of preclinical tumor models and patient tumor specimens from malignancies with known clinical outcomes to VEGFi treatment, to gain insight into potential determinants of intrinsic sensitivity and resistance.

EXPERIMENTAL DESIGN

The tumor stroma architecture of preclinical and clinical tumor samples were analyzed by staining for CD31 and α-smooth muscle actin (α-SMA). Tumor models representative of each phenotype were then tested for sensitivity to the VEGFR2-blocking antibody DC101.

RESULTS

Human tumor types with high response rates to VEGF inhibitors (e.g., renal cell carcinoma) have vessels distributed amongst the tumor cells (a "tumor vessel" phenotype, TV). In contrast, those malignancies where single-agent responses are lower, such as non-small cell lung cancer (NSCLC), display a complex morphology involving the encapsulation of tumor cells within stroma that also supports the majority of vessels (a "stromal vessel" phenotype). Only 1 of 31 tumor xenograft models displayed the stromal vessel phenotype. Tumor vessel models were sensitive to VEGFR2-blocking antibody DC101, whereas the stromal vessel models were exclusively refractory. The tumor vessel phenotype was also associated with a better Response Evaluation Criteria in Solid Tumors (RECIST) response to bevacizumab + chemotherapy in metastatic colorectal cancer (CRC).

CONCLUSION

The tumor stromal architecture can differentiate between human tumor types that respond to a VEGF signaling inhibitor as single-agent therapy. In addition to reconciling the clinical experience with these agents versus their broad activity in preclinical models, these findings may help to select solid tumor types with intrinsic sensitivity to a VEGFi or other vascular-directed therapies.

Autocrine GM-CSF transcription in the leukemic progenitor cell line KG1a is mediated by the transcription factor ETS1 and is negatively regulated through SECTM1 mediated ligation of CD7

BACKGROUND

CD7 expression is found on ~30% of acute myeloblastic leukemias (AML). The leukemic progenitor cell line KG1a (CD7+) constitutively expresses GM-CSF while the parental KG1 (CD7-) cell line does not. This study focuses on the molecular basis of CD7 mediated GM-CSF regulation.

METHODS

KG1a cells were treated with recombinant SECTM1-Fc protein, the PI3K kinase inhibitors wortmannin, LY292004, or PI4K activator spermine. Stable KG1-CD7+, KG1a-shCD7, KG1a-shETS1 as well as KG1a-GFP, KG1a-PKCβII-GFP cell lines were generated and the levels of CD7, GM-CSF and ETS-1 mRNA and protein were compared by real-time-PCR, western blotting, flow cytometry and ELISA.

RESULTS

SECTM1 is expressed in Human Bone Marrow Endothelial Cells (HBMEC) and its expression can be upregulated by both IFN-γ. KG1a cells demonstrated high expression levels of CD7 and ETS-1 allowing a constitutative signaling through the PI3K/Atk pathway to promote GM-CSF expression, while KG1 cells with low expression of CD7 and ETS-1 showed low GM-CSF expression. On KG1a cells GM-CSF expression could be negatively regulated by PI3K inhibitors or by recombinant SECTM1-Fc. Overexpression of CD7 in KG1 cells was insufficient to promote GM-CSF expression, while silencing of CD7 or ETS-1 resulted in reduced GM-CSF expression levels. Differentiation capable KG1a cells overexpressing PKCβII illustrated complete loss of CD7, but maintained normal levels of both ETS-1 and GM-CSF expression.

CONCLUSION

These findings add an additional layer to the previously described autocrine/paracrine signaling between leukemic progenitor cells and the bone marrow microenvironment and highlight a role for SECTM1 in both normal and malignant hematopoiesis.

GENERAL SIGNIFICANCE

This work shows that SECTM1 secreted from bone marrow stromal cells may interact with CD7 to influence GM-CSF expression in leukemic cells.

A randomised prospective trial of intra-operative oesophageal Doppler-guided fluid administration in major gynaecological surgery

Intra-operative oesophageal Doppler monitor-guided fluid management has been associated with improved postoperative length of hospital stay and morbidity in gastrointestinal and orthopaedic surgery. We designed a randomised controlled trial to test the hypothesis that this approach to intra-operative fluid management in major elective open gynaecological surgery would shorten the length of postoperative stay, defined as time to readiness for hospital discharge. Postoperative morbidity was evaluated as a secondary outcome. The oesophageal Doppler monitor group underwent intra-operative fluid management using an oesophageal Doppler-guided stroke volume optimisation algorithm. Control group (conventional fluid therapy) intra-operative fluid management was based on conventional haemodynamic indices. In a single centre, 102 patients were randomly assigned: 51 to the oesophageal Doppler monitor group (51 analysed) and 51 to the control group (50 analysed). Evaluators who were blinded to patient assignment collected postoperative outcome data. There was no difference in the length of postoperative hospital stay between the groups: median (IQR [range]) number of days until ready for discharge was 6 (5-8 [4-25]) days in the oesophageal Doppler monitor group compared with 7 (5-9 [4-42]) days in the control group, p = 0.5. There was no difference between the groups in postoperative morbidity survey scores on postoperative days 1, 3 or 5. Seven patients in the oesophageal Doppler monitor group and 11 in the control group experienced postoperative complications (p = 0.41). These findings question whether intra-operative oesophageal Doppler-guided fluid therapy is of benefit in patients undergoing open gynaecological surgery.

Tumor stromal architecture can define the intrinsic tumor response to VEGF-targeted therapy

PURPOSE

The aim of the study was to investigate the vascular and stromal architecture of preclinical tumor models and patient tumor specimens from malignancies with known clinical outcomes to VEGFi treatment, to gain insight into potential determinants of intrinsic sensitivity and resistance.

EXPERIMENTAL DESIGN

The tumor stroma architecture of preclinical and clinical tumor samples were analyzed by staining for CD31 and α-smooth muscle actin (α-SMA). Tumor models representative of each phenotype were then tested for sensitivity to the VEGFR2-blocking antibody DC101.

RESULTS

Human tumor types with high response rates to VEGF inhibitors (e.g., renal cell carcinoma) have vessels distributed amongst the tumor cells (a "tumor vessel" phenotype, TV). In contrast, those malignancies where single-agent responses are lower, such as non-small cell lung cancer (NSCLC), display a complex morphology involving the encapsulation of tumor cells within stroma that also supports the majority of vessels (a "stromal vessel" phenotype). Only 1 of 31 tumor xenograft models displayed the stromal vessel phenotype. Tumor vessel models were sensitive to VEGFR2-blocking antibody DC101, whereas the stromal vessel models were exclusively refractory. The tumor vessel phenotype was also associated with a better Response Evaluation Criteria in Solid Tumors (RECIST) response to bevacizumab + chemotherapy in metastatic colorectal cancer (CRC).

CONCLUSION

The tumor stromal architecture can differentiate between human tumor types that respond to a VEGF signaling inhibitor as single-agent therapy. In addition to reconciling the clinical experience with these agents versus their broad activity in preclinical models, these findings may help to select solid tumor types with intrinsic sensitivity to a VEGFi or other vascular-directed therapies.

RNA-Seq Differentiates Tumour and Host mRNA Expression Changes Induced by Treatment of Human Tumour Xenografts with the VEGFR Tyrosine Kinase Inhibitor Cediranib

Pre-clinical models of tumour biology often rely on propagating human tumour cells in a mouse. In order to gain insight into the alignment of these models to human disease segments or investigate the effects of different therapeutics, approaches such as PCR or array based expression profiling are often employed despite suffering from biased transcript coverage, and a requirement for specialist experimental protocols to separate tumour and host signals. Here, we describe a computational strategy to profile transcript expression in both the tumour and host compartments of pre-clinical xenograft models from the same RNA sample using RNA-Seq. Key to this strategy is a species-specific mapping approach that removes the need for manipulation of the RNA population, customised sequencing protocols, or prior knowledge of the species component ratio. The method demonstrates comparable performance to species-specific RT-qPCR and a standard microarray platform, and allowed us to quantify gene expression changes in both the tumour and host tissue following treatment with cediranib, a potent vascular endothelial growth factor receptor tyrosine kinase inhibitor, including the reduction of multiple murine transcripts associated with endothelium or vessels, and an increase in genes associated with the inflammatory response in response to cediranib. In the human compartment, we observed a robust induction of hypoxia genes and a reduction in cell cycle associated transcripts. In conclusion, the study establishes that RNA-Seq can be applied to pre-clinical models to gain deeper understanding of model characteristics and compound mechanism of action, and to identify both tumour and host biomarkers.

Tumor-induced STAT3 hyperactivation creates a dendritic cell differentiation block by significantly downregulating protein kinase C βII expression (P2003)

Tumor mediated blockade of dendritic cell (DC) differentiation is a large component of cancer induced immunosuppression, contributing to tumor outgrowth. Tumors impair DC differentiation via factors that hyperactivate STAT3 in DC progenitors, though the mechanisms by which this occurs are largely unknown. PKCβII is essential in DC differentiation, and we test here if tumor driven STAT3 hyperactivation downregulates PKCβII expression, and if this is the mechanism underlying impaired DC differentiation. Myeloid cells from tumor bearing mice have significantly decreased PKCβII expression. Culture in tumor conditioned media (TCM) significantly decreased PKCβII expression and significantly impaired phorbol ester driven DC differentiation in human monocytes and in a human cell line model (KG1). In KG1, this was dependent on PKCβII downregulation: enforced PKCβII expression preserved phorbol ester driven DC differentiation in the face of TCM. Interestingly, PKCβII overexpression and/or activation also antagonized TCM-driven STAT3 activation. STAT3 drives this decreased PKCβII expression: TCM induced STAT3 activation and drove 4.5 fold higher STAT3 binding to the PKCβ promoter (compared to media control, p&lt;0.001). Mutation of a STAT3 consensus binding site in the promoter eliminates the ability of STAT3 to impair PKCβ promoter activity. Together, these observations argue that tumor driven STAT3 hyperactivation inhibits DC differentiation by downregulating PKCβII.

CD28 promotes long lived plasma cell survival, sustained antibody responses and upregulation of BLIMP-1 expression through its distal proline motif. (P1475)

Durable humoral immunity is dependent upon the long term maintenance of serum antibody titers. Evidence now suggests that antibody levels are maintained by a distinct subset of bone marrow resident long lived plasma cells (LLPC). However, the molecular basis for the longevity of LLPC is largely uncharacterized. We have recently shown that CD28 signaling supports the survival and function of LLPC but not short lived splenic PC (SLPC). We have now extended these studies by characterizing the signaling pathways and molecular targets downstream of CD28 in PCs using CD28 knock-in mice in which the CD28 cytoplasmic tail is mutated at either the Y170MNM (CD28-Y170F) or P187YAP190 (CD28-AYAA) regions, resulting in loss of downstream PI3K or Grb2-Vav signaling, respectively. Interestingly, only the CD28-AYAA animals had significantly diminished LLPC numbers with no effect on SLPC numbers in vivo, consistent with the inability of CD28 activation to rescue CD28-AYAA LLPC from serum starvation-induced death in vitro. Further characterization of the CD28 (PYAP)-Vav-NFκB pathway in PC uncovered a previously undescribed regulation of the central transcription regulator BLIMP-1 through a CD28 responsive element in the prdm1 promoter. These results demonstrate that CD28 (PYAP)-Vav-NFκB activation in LLPC but not SLPC induces BLIMP-1 expression, which then can regulate the broader transcriptional reprogramming allowing for LLPC function and survival.

Expression of stromal genes associated with the angiogenic response are not differentiated between human tumour xenografts with divergent vascular morphologies

Human tumour xenografts have commonly been used to explore the mechanisms of tumour angiogenesis and the interaction of tumour cells with their microenvironment, as well as predict potential utility of anti-angiogenic inhibitors across different tumour types. To investigate how well human tumour xenografts can be used to differentiate the effects of stromal targeting agents we performed a comparative assessment of the murine angiogenic response across a panel of pre-clinical tumour xenografts. By analysing a panel of 22 tumour xenografts with a range of vascular morphologies, micro-vessel densities and levels of fibroblast and inflammatory infiltrate, we have examined the relationship between angiogenic stroma and human tumour models. These models were studied using a combination of immunohistochemistry and species specific mRNA profiling to differentiate the tumour and stromal transcript mRNA profiles. Principal Component Analysis (PCA) and regression analysis was used to investigate the transcriptional relationships between the individual models and the correlation with the stromal architecture. We found the human tumour cell expressed factors to be independent of the murine host responses such as microvessel density, and fibroblast or macrophage cellular infiltrate. Moreover mRNA profiling of the mouse stroma suggested that the host response to the different tumours was relatively uniform despite differences in stromal structures within the tumour. Supporting this, models with different stromal compositions responded similarly to cediranib, a small molecule inhibitor of VEGF signalling. The data indicate that although the angiogenic response to the tumour results in reproducible stromal architectures, these responses are not differentiated at the level of gene expression.

Abstract B127: Establishment and characterization of in vitro co-culture assays comprising tumor and fibroblast cells that more closely model the cell/stroma interactions of human tumors

Human solid tumours are comprised of epithelial cells interacting with a surrounding stroma or microenvironment. The stroma consists of several cell types including immune cells, endothelial cells and fibroblasts as well as macromolecules constituting the extracellular matrix. It has become clear from both pre-clinical and clinical studies that the tumour stroma plays a critical role in tumour progression and response to therapeutics. TGF-b is one of a number of pivotal regulators of the tumour microenvironment. Among its roles, TGF-b drives the cross-talk between tumour cells and fibroblasts resulting in a cancer associated fibroblast phenotype. This activated CAF state is linked to increased progression and survival of tumour cells and response of tumours to therapeutics.

Modeling this cross-talk is challenging however we have developed in vitro assays using tumour cells from a range of tissue types, for example NSCLC, breast, pancreatic and prostate, co-cultured with normal human fibroblasts and assessed cell/cell and cell/extracellular matrix interactions using a range of end-points including -smooth muscle actin and fibronectin. We have further characterized the assays, for NSCLC cell lines, using pharmacologically active agents to modulate canonical and non-canonical TGF-beta signaling pathways and assessed the effects on tumour cell growth, fibroblast activation and secretion of key growth factors, cytokines and proteases. We have also used RNA expression profiling of a selection of genes to investigate signaling pathways activated in tumour and fibroblast co-cultures compared to when the cells are grown as monocultures.

We will describe the development of methods to establish and quantify the different end-points explored in tumour and fibroblast co-culture assays and show data using inhibitors to validate these methods with NSCLC cell lines. We will show data from further comparison of monocultures and co-cultures by analysis of RNA and protein in cell lysates and conditioned media samples.

The development of more complex in vitro assays with more than a single cell type allows greater insight into the various tumour-stromal interactions that take place in tumours in vivo. This allows early understanding and testing of agents which may provide therapeutic benefit in limiting tumour-stromal interactions and signalling in patients.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr B127.

Abstract A13: Characterization of CRC primary explant models in comparison to standard human tumor cell-line-derived CRC xenografts

Primary tumor xenograft models (PTX) are established in immunodeficient mice by implantation of material directly from patient tumors. These models are propagated in vivo so that they are not subjected to additional selection pressures within tissue culture. The models reputedly reflect a greater genetic diversity of disease than can be recapitulated within tumor cell line derived xenografts and may have morphological differences. Consequently, such models may be of greater relevance for the evaluation of drug efficacy.

To verify differences versus cell line derived xenograft models, we have examined samples of 42 CRC PTX models, derived from Dukes stage A-D tumor samples, which were obtained from European contract research organisations) Characterisation included analysis of common genetic mutations (KRas, BRAF, PI3Ka, PTEN, P53 and APC), mRNA expression via microarray platforms (Affymetrics HG_U133_plus_2), high-throughput RT-PCR of specific probes (mouse and human) to examine stromal genes, and the activation of particular proteins using reverse phase antibody arrays and immunohistochemistry. Comparisons were made with 6 commonly used CRC cell line derived xenografts.

The PTX models overall represent a broader range of molecular pathology - for example the inclusion of wild-type Kras tumors. Histopathological characterisation also confirmed that the PTX models have a higher stromal content that is routinely observed in cell line derived xenografts, and a more complex morphology with higher tumor cell differentiation.

PTX models may potentially complement drug discovery activities by providing a wider platform in which to test preclinical hypotheses - based upon a defined biological mechanism and/or a genetic determinant of sensitivity.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr A13.

Abstract 1564: Investigating the interaction of tumor xenografts with their microenvironment by combining human- and mouse- specific assays with high throughput RT-qPCR

Tumour growth is governed by the interaction with its microenvironment through pathways that regulate tumour cell function, angiogenesis, and recruitment of associated stromal cells and immune infiltrate. These complicated biological networks can be studied in tumour xenografts using a combination of gene expression, protein and histological analysis. The majority of gene expression studies either probe expression of specific transcripts by RT-qPCR, or use broad Affymetrix microarrays to examine 1000s of genes. RT-PCR experiments may be too focussed studying the interaction of a small number of pathways, while Affymetrix is often not sensitive enough to detect low abundance transcripts, or is limited by species specificity of the probe sets. For example studying tumour stromal and endothelial cells can be challenging because these cells comprise only a small proportion of the tumour. In this study we have used high throughput RT-qPCR to specifically analyse 180 human and mouse genes (or orthologues) thought to regulate key stromal/tumour interactions in a broad xenograft panel. This approach enabled us to determine the expression patterns of potential angiogenic, migratory and survival drives of a diverse range of tumour xenograft models. Across the xenograft panel these genes distinguished tumours with an Epithelial and Mesenchymal phenotype. Interestingly we find that the transcript profile of the supporting stroma (all murine transcripts) is similar between models and key genes cluster with physiological characteristics such vessel, stromal or inflammatory phenotypes. We also used this approach to assess pharmacodynamic changes in gene expression in the tumour and host compartments in response to a VEGF signalling inhibitor. Surprisingly there was little modulation in the expression of genes in the tumour cell compartment. However, there was a clear down regulation of transcripts corresponding to endothelial cells with a concomitant reduction in the tumour vasculature. This approach has enabled us to gain insight into pre-clinical models and the response to a host targetted therapy. The data provides information that enhances understanding that can be derived using histological analysis and standard protein expression.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1564. doi:10.1158/1538-7445.AM2011-1564

A molecular mechanism of tumor mediated suppression of dendritic cell differentiation (66.41)

Cancer-induced immunosuppression contributes to tumor outgrowth and occurs, in part, via tumor-mediated dysregulation of DC-differentiation, resulting in immunosuppressive immature myeloid cells and fewer dendritic cells (DCs). Tumors impair DC-differentiation via factors that hyperactivate STAT3 in DC progenitors, though the mechanisms by which this inhibits DC-differentiation are poorly defined. PKCβII is essential in DC-differentiation. Here, we hypothesize that tumor driven STAT3 activity inhibits DC-differentiation by downregulating PKCβII expression. In most breast cancer patients tested, circulating myeloid cells had significantly decreased PKCβII expression (p&lt;0.03). Myeloid cells from tumor bearing mice also had decreased PKCβII expression. In vitro, culture in tumor conditioned media (TCM) decreased PKCβII protein levels (~50%), significantly decreased PKCβII mRNA levels (p&lt;0.01) and decreased phorbol ester driven DC-differentiation (p&lt;0.01) in a human model (KG1). TCM also significantly reduced PKCβ promoter activity (p&lt;0.01). TCM drove rapid STAT3 activation and STAT3 binding to the PKCβ promoter, suggesting that STAT3 downregulates PKCβII promoter activity. Clones stably expressing a constitutive active STAT3 construct had significantly decreased PKCβII expression (p&lt;0.05), an effect blocked by STAT3 inhibitors. This argues that tumor-driven STAT3 hyperactivation downregulates PKCβII expression in DC progenitor cells, inhibiting DC-differentiation.