A gut feeling about Complement in Early Onset Colorectal Cancer

Colorectal cancer (CRC) remains the second leading cause of cancer-related death in the United States, with a significant increase in incidence observed in young adults below the screening age. We hypothesized that differences in the immune tumor microenvironment (TME) between early-onset (≤50 years) and late-onset (≥65 years) CRC drives tumor progression and responses to treatment. Our studies in a cohort of 121 patients indicate that complement pathway genes including C7 and Complement Factor D (CFD) and the anti-apoptotic gene Bcl2 are significantly increased in early onset CRC vs late onset disease. Moreover, the immune genes in this signature also correlate with progression free survival in our cohort. Analyses of this signature in an independent TCGA cohort also shows association of these genes with progression free survival. Surprisingly, tumor intrinsic CFD gain of function experiments in preclinical mouse tumor models increased tumor burden and recapitulated a subset of the early onset human immune gene signature. Inhibition of CFD, in combination with a Bcl2 inhibitor, significantly decreased clonogenic survival in human CRC lines in vitro. Our data associates a distinct complement enhanced immune microenvironment and hints at a putative role for the microbiome in shaping this immune microenvironment in younger patients with more aggressive disease. Taken together, our work highlights complement and the innate immune response as a potential contributor to early onset CRC.

Supported by grants from NIH to SA (R01 HL137779 and R01 HL143803)

A Distinct Innate Immune Signature of Early Onset Colorectal Cancer

Despite a decrease in the prevalence of colorectal cancer (CRC) over the last 40 y, the prevalence of CRC in people under 50 y old is increasing around the globe. Early onset (≤50 y old) and late onset (≥65 y old) CRC appear to have differences in their clinicopathological and genetic features, but it is unclear if there are differences in the tumor microenvironment. We hypothesized that the immune microenvironment of early onset CRC is distinct from late onset CRC and promotes tumor progression. We used NanoString immune profiling to analyze mRNA expression of immune genes in formalin-fixed paraffin-embedded surgical specimens from patients with early (n = 40) and late onset (n = 39) CRC. We found three genes, SAA1, C7, and CFD, have increased expression in early onset CRC and distinct immune signatures based on the tumor location. After adjusting for clinicopathological features, increased expression of CFD and SAA1 were associated with worse progression-free survival, and increased expression of C7 was associated with worse overall survival. We also performed gain-of-function experiments with CFD and SAA1 in s.c. tumor models and found that CFD is associated with higher tumor volumes, impacted several immune genes, and impacted three genes in mice that were also found to be differentially expressed in early onset CRC (EGR1, PSMB9, and CXCL9). Our data demonstrate that the immune microenvironment, characterized by a distinct innate immune response signature in early onset CRC, is unique, location dependent, and might contribute to worse outcomes.

Abstract PO-031: Innate immune genes distinguish the immune microenvironment of early onset colorectal cancer

Despite a decrease in the incidence of colorectal cancer (CRC) over the last 40 years, the incidence of CRC in people under 50 years old is increasing around the globe. Early onset (≤50 years old) and late onset (≥65 years old) CRC appear to have differences in their clinicopathological and genetic features, but it is unclear if there are differences in the tumor microenvironment. We hypothesized that the immune microenvironment of early onset CRC is distinct from late onset CRC and promotes tumor progression. We used Nanostring immune profiling to analyze mRNA expression of immune genes in FFPE surgical specimens from patients with early (N=40) and late onset (N=39) CRC. We found three genes, SAA1, C7, and CFD, have increased expression in early onset colorectal cancer and distinct immune signatures based on the tumor location. After adjusting for clinicopathological features, increased expression of CFD and SAA1 were associated with worse progression free survival and increased expression of C7 was associated with worse overall survival. Our data demonstrate that the immune microenvironment in early onset CRC is unique, location dependent, and associated with worse outcomes. We propose that age specific immune signatures in the colorectal immune microenvironment can be used as biomarkers for prognosis as well as the development of targeted immune modulatory agents.

Citation Format: Ivy H. Gardner, Ragavan Siddarthan, Katherine Watson, Elizabeth Dewey, Rebecca Ruhl, Xiangnan Guan, Zheng Xia, Liana V. Tsikitis, Sudarshan Anand. Innate immune genes distinguish the immune microenvironment of early onset colorectal cancer [abstract]. In: Proceedings of the AACR Virtual Special Conference on Tumor Heterogeneity: From Single Cells to Clinical Impact; 2020 Sep 17-18. Philadelphia (PA): AACR; Cancer Res 2020;80(21 Suppl):Abstract nr PO-031.

Abstract 1423: A lncRNA MEG9 protects vasculature from DNA damage

DNA damaging agents including ionizing radiation (IR) therapy are widely used in cancer patients. Previous studies have suggested that the tumor vasculature, specifically endothelial cell (ECs) dictate responses to IR. We recently showed how IR, among other DNA damaging agents, induced changes in microRNA programs and impacted tumor angiogenesis. Here, we describe how different DNA damaging agents affect long noncoding RNA (lncRNA) programs in vascular cells. Specifically, we identify lncRNA MEG9 (Maternally Expressed Gene 9 in humans, Mirg in mouse) as one of the most differentially expressed lncRNAs in angiogenic stimuli and stress responses. MEG9 is robustly induced by DNA damaging agents and suppressed by vascular growth factors. MEG9 is located in the DLK1-DIO3 imprinted cluster. Previous studies have shown how DLK1-DIO3 genes are associated with stem cell biology and with the pathogenesis of several diseases, such as cancer. Other studies have shown that microRNAs in this cluster are regulated by methylation. Consistent with this observation, we found that inhibition of DNA methylation either via 5-azacytidine or silencing of DNMT3b significantly upregulated de novo expression of MEG9. Gain and loss of function assays indicated an anti-apoptotic role of MEG9 via caspase 3/7 pathways in cultured ECs. Similarly, MEG9 inhibition decreased angiogenesis in a 3D sprouting angiogenesis assay. Interestingly, MEG9 inhibition in ECs accelerated fibrin formation suggesting a regulatory role for this lncRNA in thrombosis. Moreover, we observed that MEG9 inhibition affects vascular permeability in vitro and in vivo in bFGF-Matrigel plugs. Finally, systemic delivery of RNAi targeting Mirg (mouse MEG9) decreased tumor burden in a mouse model of triple negative mammary carcinoma. Our mechanistic studies indicated that MEG9 in ECs impacts pathways related to inflammation and thrombosis, both critical mediators of tumor responses to radiation. Taken together, our results show MEG9 as a novel DNA damage induced lncRNA with a protective role in the tumor vasculature functioning via multiple distinct mechanisms. Therefore, we propose that disruption of lncRNA MEG9 is a potent anti-angiogenic strategy that can synergize with DNA damaging agents.

Citation Format: Cristina Espinosa-Diez, Eugenia Fraile-Bethencourt, Clayton Hudson, Rebecca Ruhl, Sudarshan Anand. A lncRNA MEG9 protects vasculature from DNA damage [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 1423.

Immune microenvironments of early onset vs late onset colorectal cancers

Over the past 40 years, the incidence of rectal cancer in patients 20–39 years old has quadrupled. The immune microenvironment in colorectal cancer is a key player in disease progression, therapy response, and overall survival. However, the role of the immune microenvironment in early onset rectal cancer (less than 50 years old) has not been elucidated. We profiled the immune microenvironments of a cohort of early onset vs late onset (over 65 years) colorectal cancers from FFPE surgical specimens and biopsies from patients. We compared our dataset to a publicly available database (GSE8721) of gene expression profiles for 203 rectal cancer and 160 matched normal mucosa samples. We identified genes that were differentially expressed between early and late onset rectal cancer groups and validated our results with qPCR. Interestingly, we noted differences in immune signatures depending on the anatomical site (colon vs rectum). Two genes, FLT3 and SAA1, were found to have increased expression in both our patient samples and the GSE8721 rectal cancer database. FLT3 codes for fms-like tyrosine kinase receptor and activating mutations of this gene are present in 30% of acute myeloid leukemia cases and is associated with a worse prognosis. SAA1 codes serum amyloid A1 which is an acute phase protein that is highly expressed in response to inflammation. While FLT3 inhibitors did not directly affect tumor cell proliferation and cell death in vitro, we observed a decrease in tumor burden in vivo. Our data indicates that there are distinct changes in the immune microenvironment between early and late onset rectal cancer. We propose that understanding these changes will enable the development of age dependent immune modulation for this disease.

Differential regulation of microRNA-15a by radiation affects angiogenesis and tumor growth via modulation of acid sphingomyelinase

Activation of acid sphingomyelinase (SMPD1) and the generation of ceramide is a critical regulator of apoptosis in response to cellular stress including radiation. Endothelial SMPD1 has been shown to regulate tumor responses to radiation therapy. We show here that the SMPD1 gene is regulated by a microRNA (miR), miR-15a, in endothelial cells (ECs). Standard low dose radiation (2 Gy) upregulates miR-15a and decreases SMPD1 levels. In contrast, high dose radiation (10 Gy and above) decreases miR-15a and increases SMPD1. Ectopic expression of miR-15a decreases both mRNA and protein levels of SMPD1. Mimicking the effects of high dose radiation with a miR-15a inhibitor decreases cell proliferation and increases active Caspase-3 & 7. Mechanistically, inhibition of miR-15a increases inflammatory cytokines, activates caspase-1 inflammasome and increases Gasdermin D, an effector of pyroptosis. Importantly, both systemic and vascular-targeted delivery of miR-15a inhibitor decreases angiogenesis and tumor growth in a CT26 murine colorectal carcinoma model. Taken together, our findings highlight a novel role for miR mediated regulation of SMPD1 during radiation responses and establish proof-of-concept that this pathway can be targeted with a miR inhibitor.

Differences in the immune microenvironment between early and late-onset colon and rectal cancer

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Background: Over the past 35 years, there has been a significant increase in the number of patients below the recommended initial screening age (50 years old) diagnosed with colorectal cancer (CRC). Early onset colorectal cancer is more likely to occur in non-white patients, be located in the rectum, be diagnosed at a more advanced stage, and have concerning pathological features. The immune microenvironment in CRC is a key player in disease progression, therapy response, and overall survival. However, the role of the immune microenvironment in early onset CRC, particularly in rectal cancer has not been investigated. This study aims to characterize the immune microenvironment of early onset ( 50 years old) and late onset ( 65 years old) colon and rectal cancer patients. Methods: We used Nanostring immune profiling to analyze FFPE surgical specimens and identified genes that were differentially expressed between early and late onset colon and rectal cancer groups. We validate our results with qPCR. The differentially expressed genes in the rectal cancer cohort were compared to our analysis of a publically available database (GSE8721) of gene expression profiles for 203 rectal cancer and 160 matched normal mucosa samples. Immunohistochemistry (IHC) was performed on FFPE colorectal specimens for CXCL3. Results: Using Nanostring, we identified two genes that were differentially expressed between early and late onset colon cancer (IFITM1, CXCL3) and two genes in the rectal cancer cohort (FLT3, SAA1). CXCL3 has increased expression in late onset colon cancer utilizing qPCR and IHC. High expression of CXCL3 in both IHC and qPCR is associated with improved disease free survival. Analysis of the GSE8721 database also showed that FLT3 and SAA1 were differentially expressed in early versus late onset rectal cancer. Using qPCR, FLT3 is increased in early onset rectal cancer specimens compare to late onset rectal cancer, early and late onset colon cancer, and normal colon. Conclusions: There are distinct differences in the immune microenvironment between early and late onset colon and rectal cancer that may hold the potential for targeted therapeutics.

Abstract 601: Radiation Therapy Induces Changes in the Endothelial Methylome Affecting Pro-angiogenic Lncrna Expression

Radiation therapy is a big part of standard of care in oncology. However, in the long- term patients treated with radiation are at higher risk of suffering cardiovascular events. It is well described that the genotoxic stress induced by Ionizing radiation in normal cardiovascular tissue triggers genetic and epigenetic changes. In addition to coding mRNAs, non-coding RNAs are also highly regulated by changes in methylation and transcription, leading to a tight regulatory response to damage. Genotoxic stress induces global hypomethylation due to decreased expression of DNA methyltransferases (DNMT). We observed that DNMT1, DNMT3A, and DNMT3b are downregulated in response to radiation treatment, in a dose-response manner in human endothelial cells. We have also observed that methylation changes produced by radiation affect a specific ncRNA cluster, DLK1-DIO3. Previous results from our lab indicate that ncRNAs from this cluster are highly responsive to different genotoxic agents, including radiation. Given the essential role of microRNAs and Long non- coding RNAs (lncRNAs) from the DLK1-DIO3 cluster in cardiovascular development and aging, we are interested in understanding how the epigenetic changes induced by radiotherapy affect to lncRNAs expression, and how they influence cardiovascular health in the long term after treatment. We have identified that a specific lncRNA from the DLK1-DIO3 cluster, MEG9, increases in ECs after exposure to ionizing radiation. Interestingly, knockdown of the individual DNMTs enzymes indicates a significant upregulation of MEG9 when DNMT3b is inhibited, more so after radiation treatment. To explore the role of this lncRNA, we performed loss-of-function studies. MEG9 inhibition not only diminished proliferation but also increased apoptosis through caspase 3/7 activation. Consistent with this phenotype, knockdown of MEG9 decreases growth factor-dependent angiogenesis in a 3D fibrin gel angiogenesis assay. Taken together, our findings illustrate how DNA methylation at particular lncRNA loci can regulate their expression and drive endothelial cell fate decisions. Our work illustrates how epigenetic changes may affect the long- term cardiovascular function of cancer patients submitted to radiation therapy.

MicroRNA regulation of the MRN complex impacts DNA damage, cellular senescence, and angiogenic signaling

MicroRNAs (miRs) contribute to biological robustness by buffering cellular processes from external perturbations. Here we report an unexpected link between DNA damage response and angiogenic signaling that is buffered by a miR. We demonstrate that genotoxic stress-induced miR-494 inhibits the DNA repair machinery by targeting the MRE11a-RAD50-NBN (MRN) complex. Gain- and loss-of-function experiments show that miR-494 exacerbates DNA damage and drives endothelial senescence. Increase of miR-494 affects telomerase activity, activates p21, decreases pRb pathways, and diminishes angiogenic sprouting. Genetic and pharmacological disruption of the MRN pathway decreases VEGF signaling, phenocopies miR-494-induced senescence, and disrupts angiogenic sprouting. Vascular-targeted delivery of miR-494 decreases both growth factor-induced and tumor angiogenesis in mouse models. Our work identifies a putative miR-facilitated mechanism by which endothelial cells can be insulated against VEGF signaling to facilitate the onset of senescence and highlight the potential of targeting DNA repair to disrupt pathological angiogenesis.

microRNA-451a regulates colorectal cancer proliferation in response to radiation

BACKGROUND

Colorectal cancer (CRC) is a leading cause of cancer-related death. The biologic response of CRC to standard of care adjuvant therapies such as chemotherapy and radiation are poorly understood. MicroRNAs (miRs) have been shown to affect CRC progression and metastasis. Therefore, we hypothesized that specific miRs modulate CRC response to chemoradiation.

METHODS

In this study, we used miR expression profiling and discovered a set of microRNAs upregulated rapidly in response to either a single 2 Gy dose fraction or a 10 Gy dose of γ-radiation in mouse colorectal carcinoma models. We used gain and loss-of-function studies in 2D and 3Dcell proliferation assays and colony formation assays to understand the role of the top miR candidate from our profiling. We used Student's T-tests for simple comparisons and two-factor ANOVA for evaluating significance.

RESULTS

The most upregulated candidate at early time points in our signature, miR-451a inhibited tumor cell proliferation and attenuated surviving fraction in longer-term cultures. Conversely, inhibition of miR-451a increased proliferation, tumorsphere formation, and surviving fraction of tumor cells. Using a bioinformatics approach, we identified four genes, CAB39, EMSY, MEX3C, and EREG, as targets of miR-451a. Transfection of miR-451a decreased both mRNA and protein levels of these targets. Importantly, we found miR-451a expression was high and CAB39, EMSY levels were low in a small subset of rectal cancer patients who had a partial response to chemoradiation when compared to patients that had no response. Finally, analysis of a TCGA colorectal cancer dataset revealed that CAB39 and EMSY are upregulated at the protein level in a significant number of CRC patients. Higher levels of CAB39 and EMSY correlated with poorer overall survival.

CONCLUSIONS

Taken together, our data indicates miR-451a is induced by radiation and may influence colorectal carcinoma proliferation via CAB39 and EMSY pathways.

miR-15a regulation of endothelial radiation sensitivity in colorectal cancer

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Background: Radiation dose escalation causes significant changes within the tumor microenvironment (TME) to enhance tumor cell death including altered microRNA (miR) levels. Among endothelial miRs, we identified miR-15a exhibits dose dependent differential regulation. miR-15a targets a key determinant of endothelial cell (EC) radiosensitivity, acid sphingomyelinase (SMPD1), an enzyme that drives rapid EC apoptosis via enhanced ceramide production. In colorectal cancer (CRC) (n = 182 patients), high miR-15a is associated with worse 5-year progression free and overall survival. miR-15a also affects immune function by promoting a pro-inflammatory TME milieu. We hypothesized miR-15a inhibition will increase tumor cell death through preservation of EC SMPD1, enhancing endothelial apoptosis and inflammatory cytokine upregulation. Methods: Using TaqMan Human miR panels, miRs were profiled in human umbilical vein ECs (HUVECs) after single 2 vs 20 Gy treatment. miR-target prediction programs identified miRs targeting SMPD1. In vitro gain and loss of function studies were performed with miR transfections in HUVECs and CT26 CRC cells. CXCL10 expression was measured by qRT-PCR. Caspase 1 activation was measured by a luminescence based assay. A CT26 syngeneic CRC flank murine model was used for in vivo miR-15a inhibitor assessment administered via tail vein injection unencapsulated or encapsulated in vascular-targeted 7C1 nanoparticles. Results: Among miRs targeting SMPD1, miR-15a exhibited the greatest differential change in HUVECs 6h post-IR between low and high dose radiation. Lower dose was associated with higher miR-15a and vice versa. Further, miR-15a levels inversely correlated with SMPD1. Exogenous miR-15a significantly decreased SMPD1 mRNA and protein. miR-15a inhibition decreased proliferation in both HUVECs and CT26 cells and increased apoptosis when combined with radiation. miR-15a inhibition increased endothelial CXCL10 expression and caspase-1 activation. Both systemic and vascular-targeted miR-15a inhibitor significantly diminished tumor growth in vivo. Conclusions: Our data suggests inhibition of vascular miR-15a is sufficient to decrease tumor growth likely due to rescue of endothelial SMPD1.

Age-related differences in gene expression in colorectal cancer (CRC)

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Background: Colorectal cancer (CRC) in young patients is increasing in incidence and is associated with worse outcomes than CRC in older patients. While distinct molecular subtypes of CRC have been recently characterized, it is unclear whether there are molecular differences between the tumors of young and old patients. We sought to identify differences in gene expression of CRC between these two groups. Our discovery analysis identified a gene signature of several differentially expressed RNAs, from which we validated PEG10. The PEG10 gene on chromosome 7q21.3 has been implicated in liver, gallbladder, thyroid, and blood cancers, and is thought to play a role in cancer cell survival and regulation of apoptosis. In hepatocellular carcinoma, increased PEG10 expression has been associated with younger patient age. Methods: RNA sequencing data was obtained from The Cancer Genome Atlas (TCGA) and analyzed for differences in gene expression between patients ≤ 45 years old and those ≥ 65 years old. The identified differentially expressed genes were then validated with qPCR using human CRC tissue from patients ≤ 45 years old and those ≥ 65 years old. Results: RNA sequencing data from patients ≤ 45 years old (n = 29) and patients ≥ 65 years old (n = 299) identified seven genes with increased expression in younger patients: ZNF334 (log2 [fold change] = 2.30), DSC3 (1.78), PEG10 (1.67), CACNA1I (1.54), PKIA (1.33), MAP9 (1.27), and EPHX3 (1.17) (p < 0.07). Validation with qPCR for PEG10 was most promising, and was performed on both young (n = 10, mean age = 39) and old patient samples ( n= 8, mean age = 72). Two cancers (20%) in the young group received radiation treatment and five (50%) received chemotherapy. One cancer (12.5%) in the old group received radiation and two (25%) received chemotherapy. PEG10 had increased expression in the young group with log2 [fold change] = 3.16 (p < 0.02). Conclusions: We have identified a potentially unique gene expression signature for CRC in young patients, which includes PEG10. Functional analysis of PEG10 and other genes is underway using in vitro cell culture, archived human tumor tissue, and mouse tumor models.

Abstract 1819: Reprogramming the tumor microenvironment by targeting endothelial DNA repair

The tumor microenvironment (TME) plays a critical role in orchestrating immune infiltration, tumor progression and response to therapeutics. Therefore, strategies to manipulate the TME including cytokine gene therapy, antibodies to reverse macrophage polarization etc are under active investigation. We have identified an alternative approach to target the TME by disrupting DNA repair in the tumor endothelial cells (ECs). We discovered a seven-microRNA (miR) signature induced in ECs in in vitro and in vivo by oxidative stress and DNA damage. The top miR candidate in this signature, miR-103 altered the TME by inducing DNA damage in ECs, eliciting type I interferons, upregulating immune costimulatory receptors and decreasing PD-L1 expressing tumor associated macrophages and granulocytes. Moreover, miR-103 treatment had a paracrine effect on the tumors and upregulated Fas and TRAIL receptors. Mechanistically, these functions of miR-103 were largely due to its downregulation of the three prime exonuclease TREX1. Local, systemic or vascular targeted delivery of miR-103 decreased both angiogenesis and tumor burden in multiple mouse tumor models.

Complementary to the role of miR-103, two additional miRs in the miR signature, miRs 494 and 99b each induced senescence in the vasculature by downregulating the Mre11a-Rad50-NBN (MRN) complex. Ectopic expression of miRs 494 or 99b decreased telomerase activity, increase p21 levels with a concomitant decrease in pRb levels. Vascular targeted delivery of miR-494 decreased angiogenesis in vivo whereas systemic delivery decreased tumor growth. Interestingly, both miR mimics and the MRN knockdowns induced the transcription of a number of senescence associated genes including CD44. Taken together these data suggest that miRs 494 and 99b targeting of the MRN complex induces senescence.

The MRN complex interacts with the ATM kinase, histone H2AX and TREX1 suggesting that the miRs we identified disrupt critical nodes of a DNA Damage Response (DDR) network. Our findings reveal a complex, miR mediated cross talk between EC DNA damage pathways, the TME and tumor cells. These interactions can be exploited for designing therapies that synergize with tumor cell killing to enhance host anti-tumor responses.

Citation Format: Cristina Espinosa-Diez, RaeAnna Wilson, Rebecca Ruhl, Nathan Kanner, Namita Chatterjee, Clay Hudson, Sudarshan Anand, Shushan Rana. Reprogramming the tumor microenvironment by targeting endothelial DNA repair [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 1819. doi:10.1158/1538-7445.AM2017-1819

Abstract 829: MicroRNA regulation of radiation sensitivity in colorectal cancer

Background Patients with locally advanced rectal cancer receive neoadjuvant chemoradiation therapy (CRT) and subsequent surgery. While 10-25% of patients have complete response to CRT, the remaining patients undergo extensive tumor excision resulting in significant quality of life issues. Response to CRT is an independent predictor of overall survival highlighting the importance of improving CRT response rates. Several tumor intrinsic factors govern responses to CRT including specific gene expression programs. Emerging evidence suggests that microRNAs (miRs) modulate gene expression programs in response to radiation and have been implicated in several pathological processes associated with colorectal cancer progression. In this context, we hypothesized that differential expression of miRs regulates colorectal cancer radiation sensitivity and can be used as a biomarker to predict radiation efficacy.

Methods To investigate the differences in miR profiles between rectal cancer patients that had either a pathological partial response (PR) or no response (NR), we isolated RNA from FFPE biopsies using the miRvana microRNA isolation kit (Life Technologies). We used the Nanostring miR profiling platform and obtained absolute counts for &gt;700 human miRs. We performed in vitro gain and loss of studies with candidate miR transfections in human CRC cell lines and used a luminescence-based assay for proliferation (Cell titer glo, Promega). Surviving fraction assays were performed by seeding cells and counting colonies stained with Crystal Violet. Eight distinct miR bioinformatic target prediction algorithms initiated miR target identification, and a RISC-Trap assay was implemented to confirm miR-target interactions. The Cancer Genome Atlas (TCGA) datasets were accessed to acquire provisional survival data on 639 colorectal adenocarcinoma patients.

Results We identified 17 miRs that were differentially expressed, and miR-451a, among the most upregulated miRs, inhibited proliferation and colony formation in 2D and 3D assays in the presence of radiation. Target prediction algorithms highlighted CAB39, EMSY, EREG, and MEX3C as prominent miR-451a targets in colorectal cancer and/or radiation. TCGA subset anaylsis found CAB39 and EMSY protein levels were found to be upregulated in 14% and 6% of cases, respectively, and upregulated co-expression of these genes significantly reduced 3 year overall survival (69% vs 78%, p &lt; 0.05). miR-target interaction was confirmed via the RISC-Trap assay with miR-451a mimic transfection resulting in robust 2.4-, 1.2-, and 2.8-fold enrichment of EREG, CAB39, and EMSY, respectively. In our partial responders patient cohort possessing upregulated miR-451a, there was significant downregulation of CAB39 and EMSY mRNA and protein compared to non-responders.

Conclusions miRs alter cell survival networks affecting radiation sensitivity and serve to identify pathways amenable to alternative therapeutic modulation

Citation Format: Shushan Rana, Katherine Kelley, Rebecca Ruhl, Charles Thomas, Liana Tsikitis, Sudarshan Anand. MicroRNA regulation of radiation sensitivity in colorectal cancer [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 829. doi:10.1158/1538-7445.AM2017-829

Colorectal Cancer Liver Metastasis: Evolving Paradigms and Future Directions

In patients with colorectal cancer (CRC) that metastasizes to the liver, there are several key goals for improving outcomes including early detection, effective prognostic indicators of treatment response, and accurate identification of patients at high risk for recurrence. Although new therapeutic regimens developed over the past decade have increased survival, there is substantial room for improvement in selecting targeted treatment regimens for the patients who will derive the most benefit. Recently, there have been exciting developments in identifying high-risk patient cohorts, refinements in the understanding of systemic vs localized drug delivery to metastatic niches, liquid biomarker development, and dramatic advances in tumor immune therapy, all of which promise new and innovative approaches to tackling the problem of detecting and treating the metastatic spread of CRC to the liver. Our multidisciplinary group held a state-of-the-science symposium this past year to review advances in this rapidly evolving field. Herein, we present a discussion around the issues facing treatment of patients with CRC liver metastases, including the relationship of discrete gene signatures with prognosis. We also discuss the latest advances to maximize regional and systemic therapies aimed at decreasing intrahepatic recurrence, review recent insights into the tumor microenvironment, and summarize advances in noninvasive multimodal biomarkers for early detection of primary and recurrent disease. As we continue to advance clinically and technologically in the field of colorectal tumor biology, our goal should be continued refinement of predictive and prognostic studies to decrease recurrence after curative resection and minimize treatment toxicity to patients through a tailored multidisciplinary approach to cancer care.

MicroRNA regulation of radiation sensitivity in colorectal cancers

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Background: Patients with locally advanced colorectal cancer (T3/T4/Node positive) receive neoadjuvant chemoradiation therapy (CRT) and subsequent surgery. While 10-25% of patients have complete response to CRT, the remaining patients undergo extensive tumor excision that leads to quality of life issues. Response to CRT is an independent predictor of overall survival highlighting the importance of improving CRT response rates. Several tumor intrinsic factors govern responses to CRT including specific gene expression programs. Emerging evidence suggests that microRNAs (miRs) modulate gene expression programs in response to radiation. Moreover, miR-processing machinery is frequently mutated in colorectal cancers (TCGA, 2016 provisional). miRs have been implicated in several pathological processes associated with colorectal cancer progression including cancer stemness and epithelial-to-mesenchymal transition (EMT). In this context, we hypothesized that differential expression of miRs regulates colorectal cancer radiation sensitivity and therefore can be used as a biomarker to predict therapeutic responses to radiation. Methods: To investigate the differences in miR profiles between rectal cancer patients that had either a pathological partial response (PR) or no response (NR), we isolated RNA from FFPE biopsies using the miRvana microRNA isolation kit (Life Technologies). We used the Nanostring miR profiling platform and obtained absolute counts for > 700 human miRs of which ~500 miRs were expressed above detection limits (cut-off of 20 counts after normalization to the top-100 miRs). We performed in vitro gain and loss of studies with miR transfections in human CRC cell lines with RNAimax reagent and used a luminescence-based assay for proliferation (Cell titer glo, Promega). We performed surviving fraction assays by seeding cells on 6 well plate and counting colonies stained with Methylene Blue. Results: We identified seventeen miRs that were differentially expressed. Among the most upregulated in this group, miR-451a, inhibited proliferation and colony formation in 2D and 3D assays in the presence of radiation. Conclusions: Our data suggests miRs may alter cell survival pathways and affect tumor radiosensitivity.

Colorectal Cancer Liver Metastasis: Evolving Paradigms and Future Directions

In patients with colorectal cancer (CRC) that metastasizes to the liver, there are several key goals for improving outcomes including early detection, effective prognostic indicators of treatment response, and accurate identification of patients at high risk for recurrence. Although new therapeutic regimens developed over the past decade have increased survival, there is substantial room for improvement in selecting targeted treatment regimens for the patients who will derive the most benefit. Recently, there have been exciting developments in identifying high-risk patient cohorts, refinements in the understanding of systemic vs localized drug delivery to metastatic niches, liquid biomarker development, and dramatic advances in tumor immune therapy, all of which promise new and innovative approaches to tackling the problem of detecting and treating the metastatic spread of CRC to the liver. Our multidisciplinary group held a state-of-the-science symposium this past year to review advances in this rapidly evolving field. Herein, we present a discussion around the issues facing treatment of patients with CRC liver metastases, including the relationship of discrete gene signatures with prognosis. We also discuss the latest advances to maximize regional and systemic therapies aimed at decreasing intrahepatic recurrence, review recent insights into the tumor microenvironment, and summarize advances in noninvasive multimodal biomarkers for early detection of primary and recurrent disease. As we continue to advance clinically and technologically in the field of colorectal tumor biology, our goal should be continued refinement of predictive and prognostic studies to decrease recurrence after curative resection and minimize treatment toxicity to patients through a tailored multidisciplinary approach to cancer care.

Abstract 1111: Reprogramming the breast cancer microenvironment using microRNAs that target DNA repair

Preclinical and clinical studies have revealed that tumor endothelium is abnormal, resistant to genotoxic stress, and as such, functions as a key determinant of therapeutic responses to radiation and chemotherapy. While it is well established that radiation and chemotherapy cause DNA damage in tumor vasculature, the molecular mechanisms leading to subsequent cell cycle arrest, apoptosis or senescence in vascular cells are poorly understood. Therefore, identifying and understanding factor(s) that mediate DNA damage responses in tumor endothelial cells will provide potential targets for sensitizing tumor vasculature to radiation and other DNA damaging agents and improve their therapeutic efficacy in cancer.

Recent data indicates that microRNAs (miRs) are potent regulators of DNA damage responses in the tumor microenvironment. miRs are short 20-22 nucleotide (nt) RNA molecules that regulate gene expression by binding to partially complementary sites in target mRNAs. Since miRs mediate several physiological processes in endothelial cells, we hypothesized that miRs regulate endothelial (EC) DNA damage responses. We used an expression screen to identify miRs induced by radiation, cisplatin or hydrogen peroxide in human ECs and identified seven specific miRs unique to intrinsic EC apoptosis pathways regulated by genotoxic stress. In vitro gain-of-function assays show that three of them, miR-21, miR-99b and miR-494 lead to endothelial senescence by impairing telomerase function and inhibit sprouting angiogenesis in vitro, in a 3D assay. Strikingly, we observed that these three miRs each target every member of the MRN (Mre11a-Rad50 and NBS1) complex, a critical part of the cellular DNA repair machinery. MRN complex plays a vital role in DNA ds break repair, replication, and telomere maintenance. Pulldown of a mutant RNA Induced Silencing Complex (RISC) from cells transfected the miR mimics enriched for the MRN mRNAs suggesting direct miRNA-MRN complex mRNA binding. Consistent with these results, knockdown of the MRN complex recapitulated the effects of the miRs, reproducing the senescence phenotype, angiogenesis inhibition and also impaired telomerase activity.

Since MRE-11a is upregulated in human breast cancer patients, we asked if there was any differential expression of miR-494 in either the tumor ECs or tumor cells. Interestingly, ISH of a breast cancer tissue array revealed a significant reduction in tumor miR-494 levels compared with the adjacent normal tissue. Furthermore, ectopic expression of miR-494 diminished breast cancer cell proliferation in 2D and 3D.

Our observations indicate that miR-494 behaves as a tumor suppressor microRNA by targeting the MRN complex, inducing senescence, cell cycle arrest and decreases angiogenesis. Therefore, we propose that restoration of these miRs targeting the MRN complex in breast cancer is likely to synergize with DNA damaging agents and decrease tumor burden.

Citation Format: Cristina Espinosa-Diez, RaeAnna Wilson, Nathan Kanner, Rebecca Ruhl, Christina M. Hipfinger, Sudarshan Anand. Reprogramming the breast cancer microenvironment using microRNAs that target DNA repair. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1111.

Novel cellular genes essential for transformation of endothelial cells by Kaposi's sarcoma-associated herpesvirus

Kaposi's sarcoma-associated herpesvirus (KSHV) is involved in the development of lymphoproliferative diseases and Kaposi's sarcoma. The oncogenicity of this virus is reflected in vitro by its ability to transform B cells and endothelial cells. Infection of dermal microvascular endothelial cells (DMVEC) transforms the cells from a cobblestone-like monolayer to foci-forming spindle cells. This transformation is accompanied by dramatic changes in the cellular transcriptome. Known oncogenes, such as c-Kit, are among the KSHV-induced host genes. We previously showed that c-Kit is an essential cellular component of the KSHV-mediated transformation of DMVEC. Here, we test the hypothesis that the transformation process can be used to discover novel oncogenes. When expression of a panel of KSHV-induced cellular transcripts was inhibited with antisense oligomers, we observed inhibition of DMVEC proliferation and foci formation using antisense molecules to RDC1 and Neuritin. We further showed that transformation of KSHV-infected DMVEC was inhibited by small interfering RNA directed at RDC1 or Neuritin. Ectopic expression of Neuritin in NIH 3T3 cells resulted in changes in cell morphology and anchorage-independent growth, whereas RDC1 ectopic expression significantly increased cell proliferation. In addition, both RDC1- and Neuritin-expressing cells formed tumors in nude mice. RDC1 is an orphan G protein-coupled receptor, whereas Neuritin is a growth-promoting protein known to mediate neurite outgrowth. Neither gene has been previously implicated in tumorigenesis. Our data suggest that KSHV-mediated transformation involves exploitation of the hitherto unrealized oncogenic properties of RDC1 and Neuritin.

Human immunodeficiency virus (HIV) type 1 Vpu induces the expression of CD40 in endothelial cells and regulates HIV-induced adhesion of B-lymphoma cells

AIDS-related B-cell non-Hodgkin's lymphoma (AIDS-NHL) is a significant cause of morbidity and mortality among individuals infected with human immunodeficiency virus type 1 (HIV-1). AIDS-NHL is clinically and histologically heterogeneous, but common features include an aggressive clinical course and frequent extranodal presentation. HIV-1 infection of nonimmune cells that interact with malignant B cells at extranodal sites may influence both the development and the clinical presentation of disease. Our previous studies have shown that coculture of B-lymphoma (BL) cells with HIV-1-infected endothelial cells (EC) leads to contact activation of EC and firm BL-cell adhesion. The key event promoting EC-BL-cell adhesion was HIV-1 upregulation of endothelial CD40, which allowed induction of vascular cell adhesion molecule 1 (VCAM-1) in a CD40-dependent manner. The present study was designed to identify the HIV-1 protein(s) that influence EC-BL-cell adhesion. When HIV-1 proteins were individually expressed in EC by using recombinant adenoviruses, cultured BL cells adhered exclusively to Vpu-transduced EC. As with HIV-infected EC, adhesive properties were linked to the capacity of Vpu to upregulate CD40, which in turn allowed efficient expression of VCAM-1. When EC were infected with an HIV-1 pseudotype lacking the Vpu gene, CD40 upregulation and BL-cell adhesive properties were lost, indicating an essential role for Vpu in EC-BL-cell interactions. Thus, these data reveal a novel function for HIV-1 Vpu and further suggest a role for Vpu in the development of AIDS-NHL at EC-rich extranodal sites.

A functional genomics approach to Kaposi's sarcoma

Kaposi's sarcoma (KS) is the most frequent malignancy afflicting acquired immune-deficiency syndrome (AIDS) patients. Tumor lesions are characterized by spindle cells of vascular origin and vascularization. Kaposi's sarcoma-associated herpes virus (KSHV) is consistently found in all forms of KS. Infection of dermal microvascular endothelial cells (DMVEC) with KSHV recapitulates spindle cell formation in vitro. We studied this transformation process by DNA microarray analysis comparing the RNA expression profiles of KSHV-infected and mock-infected DMVEC. Genes involved in tumorigenesis, angiogenesis, host defense, cell growth and differentiation, transcription, and metabolism were observed to change significantly upon infection with KSHV. One of the most consistently KSHV-induced genes was the receptor tyrosine kinase and proto-oncogene c-Kit. Inhibition of c-Kit activity with the pharmacological inhibitor of c-Kit signaling STI571 reversed the KSHV-induced morphological transformation of DMVEC. Moreover, overexpression studies showed that c-Kit was sufficient to induce spindle cell formation (Moses et al. J. Virol. 76(16): 8383-8399). These data demonstrate that microarrays are useful for the identification of pharmacological targets essential for KS tumorigenesis.

Kaposi's sarcoma-associated herpesvirus-induced upregulation of the c-kit proto-oncogene, as identified by gene expression profiling, is essential for the transformation of endothelial cells

Kaposi's sarcoma (KS), the most frequent malignancy afflicting AIDS patients, is characterized by spindle cell formation and vascularization. Infection with KS-associated herpesvirus (KSHV) is consistently observed in all forms of KS. Spindle cell formation can be replicated in vitro by infection of dermal microvascular endothelial cells (DMVEC) with KSHV. To study the molecular mechanism of this transformation, we compared RNA expression profiles of KSHV-infected and mock-infected DMVEC. Induction of several proto-oncogenes was observed, particularly the receptor tyrosine kinase c-kit. Consistent with increased c-Kit expression, KHSV-infected DMVEC displayed enhanced proliferation in response to the c-Kit ligand, stem cell factor (SCF). Inhibition of c-Kit activity with either a pharmacological inhibitor of c-Kit (STI 571) or a dominant-negative c-Kit protein reversed SCF-dependent proliferation. Importantly, inhibition of c-Kit signal transduction reversed the KSHV-induced morphological transformation of DMVEC. Furthermore, overexpression studies showed that c-Kit was sufficient to induce spindle cell formation. Together, these data demonstrate an essential role for c-Kit in KS tumorigenesis and reveal a target for pharmacological intervention.

Long-term infection and transformation of dermal microvascular endothelial cells by human herpesvirus 8

Human herpesvirus 8 (HHV8) infects Kaposi's sarcoma (KS) spindle cells in situ, as well as the lesional endothelial cells considered to be spindle cell precursors. The HHV8 genome contains several oncogenes, suggesting that infection of endothelial and spindle cells could induce cellular transformation and tumorigenesis and promote the formation of KS lesions. To investigate the potential of HHV8 infection of endothelial cells to contribute to the development of KS, we have developed an in vitro model utilizing dermal microvascular endothelial cells that support significant HHV8 infection. In contrast to existing in vitro systems used to study HHV8 pathogenesis, the majority of dermal endothelial cells are infected with HHV8 and the viral genome is maintained indefinitely. Infection is predominantly latent, with a small percentage of cells supporting lytic replication, and latency is responsive to lytic induction stimuli. Infected endothelial cells develop a spindle shape resembling that of KS lesional cells and show characteristics of a transformed phenotype, including loss of contact inhibition and acquisition of anchorage-independent growth. These results describe a relevant model system in which to study virus-host interactions in vitro and demonstrate the ability of HHV8 to induce phenotypic changes in infected endothelial cells that resemble characteristics of KS spindle cells in vivo. Thus, our results are consistent with a direct role for HHV8 in the pathogenesis of KS.

Unconventional approaches to drug therapy in severe asthma

Asthma is now considered as an inflammatory disease. A subset of severe asthmatic patients requires large doses of daily systemic steroids to achieve some control of the inflammation of the airways. To minimize the daily absorption of glucocorticoids, a number of medicaments have been studied for the last three decades. Methotrexate, dapsone, hydroxychloroquine, ciclosporine A, gold salts, intravenous gammaglobulins, ketotifen, triacetyloleandomycin, all demonstrated some positive effects in a small number of studies. However, our impression is that most "steroid-sparing" medications are either poorly effective in large series and/or have intolerable side effects in these chronically ill patients; many are very expensive. A revised, adjusted therapeutic strategy, using currently recommended anti-asthmatic drugs, making a major use of inhaled topical corticosteroids, should limit the number of "cortico-dependent" asthmatic patients.