Sporadic Cancer Research Articles

Use of Microfluidic Assays to Develop Reliable and Economic Nucleic Acid Application Technologies, Employing MicroRNAs for the Diagnostic Screening of Colon Cancer in Human Stool in Low-Resource Settings

Isolation methods that employ readily-available inexpensive supplies on the open market, which are reliable, as well as economical, such as nucleic acid amplification techniques (NAAT) based on microfluidic technology in low-resource research settings (LRRS) that meets the ASSURED guidelines are essential to develop a noninvasive diagnostic colon cancer screen in stool using micro(mi)RNA molecules. A combination of a microfluidic-based MiRNA stool test with a reliable rolling circle amplification/detection method applied to the quantification of miRNA molecules, result in an affordable sensitive and specific isothermal method for the noninvasive quantitative detection of miRNAs in LRRS. Scientists and engineers have become interested in miRNAs, and they have intensified their efforts to apply emerging simple detection tools to the important bioanalytical challenge of quantifying these small 18-26 nt long molecules. Some of the proposed approaches incorporate novel material, such as simple centrifuges and methods based on microfluidic technology, while others utilize the interesting biological properties of these molecules, such as forming branched RCA structures, allowing for the detection of these biomarker molecules at an attomolar "aM" concentration level, using low cost extraction and isothermal amplification methods in LRRS. We have been interested in studying colorectal cancer (CRC) because it is the 3rd most common malignancy worldwide, and stool can be obtained noninvasively from the patients. We have focused in this research on colon cancer (CC) because it is more common in the USA than rectal cancer (RC). The innovation of our approach lies in the exploratory use of an affordable, quantitative miRNA profiling in noninvasive stool samples in LRRS, whose extracted fragile total RNA is stabilized shortly after excretion from stool by commercially available kits, so it does not ever fragment, followed by quantitative standardized analytical tests that are neither labor intensive, nor require expensive instrumentation, in order to develop apanel of novel miRNA genes for the noninvasive diagnostic screening of early left and right sporadic colon cancers, more economically, and with higher sensitivity and specificity than any other colon cancer screening test currently available on the market. To show the clinical sensitivity and specificity of the proposed quantitative miRNA test using simple methodologies in LRRS,the miRNA results are to be correlated with FOBT, colonoscopy, and pathology data. Standardization establishes test’s performance criteria (sample selection, optimal sample running conditions, preservation and storage), in order to ensure that the assay will perform the same way in any laboratory, by any trained personnel, anywhere in low-resource laboratory settings worldwide.

Gene Mutations in Hereditary Breast Cancer- A Review

The most prevalent form of cancer in females is breast cancer. Roughly 5%-10% of breast cancers are hereditary, and they are associated with Germline gene mutations, inherited from parents. Germline gene mutations increase the risk of developing cancer earlier in life compared to noninherited cases (sporadic cancer). BRCA1 and BRCA2 are well-studied tumour suppressor genes associated with hereditary breast cancer. Even though mutations in BRCA1 and BRCA2 are assumed to responsible the majority of hereditary breast cancers cases, many other breast cancer susceptibility genes have been identified in the last few decades. Identification of many germline mutations was possible due to advance sequencing technologies. Most of these genes are belongs to tumour suppressors and DNA damage repair gene families (DNA double-strand break repair and DNA mismatch repair). These genes play a vital role in genomic stability and cell cycle control suggesting that any alteration in these genes trigger uncontrolled growth and tumour formation. These genes are categorized according to the penetrance level, the proportion of carriers express the associated trait of the mutated gene. Mutations in high penetrance genes such as BRCA1, BRCA2, TP53, PTEN, and SKT11 greatly increase the risk of developing breast cancer. Moderate penetrance gene such as PALB2, ATM, CHEK2, BARD1, BRIP1 and low penetrance gene such as PARP4, CASP8, TOX3 confer moderate to low increase risk of developing breast cancer. Aim of this review is to summarize genes associated with hereditary breast cancer according to their penetrance level (high, moderate and low penetrance).

WWP1 Gain-of-Function Inactivation of PTEN in Cancer Predisposition

BackgroundPatients with PTEN hamartoma tumor syndrome (PHTS) have germline mutations in the tumor-suppressor gene encoding phosphatase and tensin homologue (PTEN). Such mutations have been associated with a hereditary predisposition to multiple types of cancer, including the Cowden syndrome. However, a majority of patients who have PHTS-related phenotypes have tested negative for PTEN mutations. In a previous study, we found that the E3 ubiquitin ligase WWP1 negatively regulates the function of PTEN.MethodsIn a prospective cohort study conducted from 2005 through 2015, we enrolled 431 patients with wild-type PTEN who met at least the relaxed diagnostic criteria of the International Cowden Consortium. Patients were scanned for WWP1 germline variants. We used the Cancer Genome Atlas (TCGA) data set as representative of apparently sporadic cancers and the Exome Aggregation Consortium data set excluding TCGA (non-TCGA ExAC) and the noncancer Genome Aggregation Database (gnomAD) as representative of population controls without a reported cancer diagnosis. We established both in vitro and murine in vivo models to functionally characterize representative WWP1 variants.ResultsThe existence of germline WWP1 variants was first established in a family with wild-type PTEN who had oligopolyposis and early-onset colon cancers. A validation series indicated that WWP1 germline variants occurred in 5 of 126 unrelated patients (4%) with oligopolyposis as a predominant phenotype. Germline WWP1 variants, particularly the WWP1 K740N and N745S alleles, were enriched in patients who did not have PHTS but had prevalent sporadic cancers, including PTEN-related cancer types in TCGA (odds ratio, 1.5; 95% confidence interval, 1.1 to 2.1; P=0.01). The prioritized WWP1 variants resulted in gain-of-function effects, which led to aberrant enzymatic activation with consequent PTEN inactivation, thereby triggering hyperactive growth-promoting PI3K signaling in cellular and murine models.ConclusionsIn this study involving patients with disorders resulting in a predisposition to the development of multiple malignant neoplasms without PTEN germline mutations, we confirmed the function of WWP1 as a cancer-susceptibility gene through direct aberrant regulation of the PTEN–PI3K signaling axis. (Funded by the National Institutes of Health and others.)

Biomarkers for Pancreatic Neuroendocrine Neoplasms (PanNENs) Management-An Updated Review.

Pancreatic neuroendocrine tumors (PanNENs) are rare sporadic cancers or develop as part of hereditary syndromes. PanNENs can be both functioning and non-functioning based on whether they produce bioactive peptides. Some PanNENs are well differentiated while others—poorly. Symptoms, thus, depend on both oncological and hormonal causes. PanNEN diagnosis and treatment benefit from and in some instances are guided by biomarker monitoring. However, plasmatic monoanalytes are only suggestive of PanNEN pathological status and their positivity is typically followed by deepen diagnostic analyses through imaging techniques. There is a strong need for new biomarkers and follow-up modalities aimed to improve the outcome of PanNEN patients. Liquid biopsy follow-up, i.e., sequential analysis on tumor biomarkers in body fluids offers a great potential, that need to be substantiated by additional studies focusing on the specific markers and the timing of the analyses. This review provides the most updated panorama on PanNEN biomarkers.

Colorectal cancer screening in Lynch syndrome: Indication, techniques and future perspectives.

Lynch syndrome (LS) is an inherited predisposition to colorectal cancer (CRC), responsible for 3-5% of all CRC. This syndrome is characterized by the early occurrence of colorectal neoplastic lesions, with variable incidences depending on the type of pathogenic variants in MMR genes (MLH1, MSH2, MSH6, PMS2 and EPCAM) and demographics factors such as gender, body mass index, tobacco use and physical activity. Similar to sporadic cancers, colorectal screening by colonoscopy is efficient because it is associated with a reduction >50% of both CRC incidence and CRC related mortality. To that end, most guidelines recommend high definition screening colonoscopies in dedicated centers, starting at the age of 20-25years old, with a surveillance interval of 1-2years. In this review, we discuss the importance of high definition colonoscopies, including the compliance to specific key performance indicators, as well as the expected benefits of specific imaging modalities including virtual chromoendoscopy and dye-spray chromoendoscopy.

Strategy for identification of a potential inherited leukemia predisposition in a 299 patient’s cohort with tumor-only sequencing data

Myeloid neoplasms (MN) are usually sporadic late-onset cancers; nevertheless, growing evidence suggests that ∼5% of the cases could emerge as a consequence of inherited predisposition. Distinguishing somatic from germline variants is of vital importance, in order to establish an appropriate individualized management and counsel the patients and their relatives. Since many of the genes associated with myeloid neoplasm germline predisposition (MNGP) are also affected in sporadic MN, we intended to design a strategy to identify potentially inherited variants in a tumor only NGS panel in a cohort of 299 patients with a variety of MN. We considered as indicative of potential inherited origin, variants detected in BM sample at a ∼50% VAF classified as pathogenic, likely pathogenic or of unknown significance detected in MNGP-related genes. A total of 104 suspicious variants from 90 patients were filtered-in in tumor samples. Mutational patterns, follow-up data, and sequencing of a range of non-myeloid tissues were used for narrowing down the list of suspicious variants, and ultimately discriminate their nature. Our data supports the importance of considering variants found upon tumor-only sequencing as potentially of germline origin, and we offer a pipeline to define the nature of the variants.

RAS-mutated sporadic medullary thyroid cancer: A single-center experience.

6584 Background: Activating RAS mutations are recognized as important drivers in sporadic medullary thyroid cancer (sMTC), with a reported prevalence between 0-43%. However, few studies have looked at correlations between RAS-mutated sMTC and clinicopathologic features. Methods: Patients with sMTC diagnosed between 1992 – 2019 with NGS testing for RET and RAS mutations seen at a tertiary cancer center were retrospectively evaluated. The objective was to analyze demographic and clinical features among patients with RAS-mutated sMTC and to evaluate associations between these features and overall survival (OS). Analyses were performed to correlate patient demographics and pathologic staging with treatment characteristics, disease course, and OS. Results: We identified 42 patients (50% female) with RAS-mutated sMTC out of 218 pts with sMTC. Median age at diagnosis was 50 years (range 24-78 years). 26 (62%) patients had stage IV disease at time of diagnosis. 28 (67%) of patients had HRAS mutations and 14 (33%) had KRAS mutations. HRAS Q61R was the most common HRAS mutation type (n = 19, 45%). Median follow-up time was 64 months (range 23-274 months) during which 11 (26%) patients died. The median OS was 16.2 years, with 5- and 10- year OS of 88% and 73% respectively. Of the 20 (48%) patients who received systemic therapy, 79% had stage IV disease and tended to be older (median age 54). Median time from diagnosis to initiation of systemic therapy was 33 months. Factors associated with worse OS included distant metastases at diagnosis, shorter time interval between diagnosis and treatment, and Ctn/CEA doubling times < 6 months. HRAS Q61R mutations were associated with a better prognosis, with 100% 10-year OS compared with 10-year OS of 39% and 51% (p = 0.02) for other HRAS and KRAS mutations respectively. Conclusions: At a tertiary cancer center, patients with RAS-mutated sMTC had a 10-year OS rate of 73%, with significantly worse OS in patients with HRAS/KRAS mutations other than HRAS Q61R. In comparison, prior studies have reported 10-year OS rates between ~71-90% in sMTC and 10-year OS rates as low as 56% for more aggressive RET M918T sMTC mutations. The findings here are consistent with other studies that have suggested patients with RAS-mutated sMTC are at intermediate risk for aggressive disease, though there are limited data on OS rates in RAS or RAS-/RET- sMTC. Future research comparing outcomes between various RAS mutations and in comparison to RET+ and RAS-/RET- patients is needed, especially as systemic therapy use in RAS-mutated sMTC evolves.

Results from a phase II study of bevacizumab and erlotinib in subjects with advanced hereditary leiomyomatosis and renal cell cancer (HLRCC) or sporadic papillary renal cell cancer.

5004 Background: HLRCC is a familial cancer syndrome associated with a type 2 papillary RCC (pRCC) variant. HLRCC is caused by germline mutations in the gene for the Krebs cycle enzyme fumarate hydratase (FH). FH inactivation results in VHL-independent upregulation of hypoxia inducible factor, a reliance on aerobic glycolysis, and activation of the NRF2 pathway, features also shared by some sporadic pRCC tumors. We hypothesized that the metabolic alterations underlying these tumors would be susceptible to targeted therapy with a combination of bevacizumab and erlotinib. Methods: Patients with advanced pRCC were eligible to enroll on this phase II study. To enrich for patients with FH deficiency, those with 1) HLRCC and 2) sporadic pRCC were enrolled into parallel, independent cohorts. All patients received bevacizumab 10 mg/kg IV every 2 weeks and erlotinib 150 mg orally daily. Patients who had received no more than two agents targeting the VEGFR pathway were included. Patients remained on treatment until unacceptable toxicity or progression. The primary endpoint was overall response rate (ORR); secondary endpoints were progression free survival (PFS) and duration of response. Results: A total of 83 patients with pRCC, including 42 in the HLRCC cohort and 41 in the sporadic cohort were enrolled on study. The majority of patients were IMDC intermediate risk (53/83, 64%) and 27 (33%) had at least one prior treatment. The ORR was 51% (42/83; 95% CI, 40 – 61) in all patients, 64% (27/42; 95% CI, 49 – 77) in the HLRCC cohort, and 37% (15/41; 95% CI, 24 – 52) in the sporadic cohort. The median PFS was 14.2 months (95% CI, 11.4 – 18.6) in all patients, 21.1 months (95% CI, 15.6 – 26.6) in the HLRCC cohort, and 8.7 months (95% CI, 6.4 – 12.6) in the sporadic cohort. The majority of treatment related adverse events (TRAEs) were grade 1 or 2 with the most common being acneiform rash (92%), diarrhea (77%), proteinuria (71%), and dry skin (61%). Grade ≥3 TRAEs occurred in 47% of patients, including hypertension (34%) and proteinuria (13%), with one patient (1.2%) with a grade 5 GI hemorrhage possibly related to bevacizumab. Conclusions: The combination of bevacizumab and erlotinib is well tolerated and is associated with encouraging activity in advanced pRCC, particularly in patients with FH deficient tumors. This is the first and largest prospective study in HLRCC and provides the basis for considering bevacizumab and erlotinib as a preferred option in a patient population that has no widely accepted standard. Clinical trial information: NCT01130519 .

MON-519 In Silico Analysis of rs1042522 and rs1042522 Polymorphic Variants of TP53 Gene

The TP53 gene encodes the p53 protein which is a nuclear phosphoprotein that plays a key role in cell cycle regulation, especially in the transition from G0 to G1. It is located on chromosome 17 at position p13.1 and found at very low levels in normal cells, but it is expressed in large quantities in damaged cells. The most frequent alterations in the TP53 gene are point mutations that cause alteration in the base sequence, resulting in a defective protein. The most frequent alteration occurs in codon 72 (rs1042522). P72R shows an exon 4 polymorphism of the TP53 gene where it there is a substitution of an arginine (Arg) by a proline (Pro). This variant is associated with sporadic thyroid cancer. In addition, codon 72 variants decrease p53’s ability to activate apoptosis and are associated with some autoimmune diseases like Graves’ disease. The codon variant 47 (rs1800371) P47S has a rare polymorphism in the p53 N-terminal transactivation domain that replaces the serine-like wild-type proline (Ser). This variant is associated with impaired pro-apoptotic p53 activity therefore also increasing the risk of cancer. In order to better understand the role of SNPs (rs1042522) and (rs1800371), based on data obtained from the NCBI dbSNP database and UniProt, we evaluated the effect of amino acid alteration on protein structure. We used bioinformatics tools such as SIFT (Sorting Intolerant from Tolerant), Align GVGD, PolyPhen-2, SNAP (Screening for nonacceptable polymorphisms), PANTHER (Protein Analysis Through Evalutionary Relationships), PredictSNP, nsSNPAnalyzer, PROVEAN, SNP & GO, PMut and MuPRO. Rs1042522 and rs1800371 bioinformatic analysis suggested that the amino acid change alters protein structure (Align GVGD tool), decreases the stability (MuPro tool) and function (SNAP) of the protein. SNPs & GO confirmed an association of these polymorphisms with different diseases. We conclude that SNPs rs1042522 and rs1800371 are important in the process of tumorigenesis, corroborating findings from our group and others that suggest that they difficult the action of p53 protein.

Pathogenic Variants in CHEK2 Are Associated With an Adverse Prognosis in Symptomatic Early-Onset Breast Cancer.

Checkpoint kinase 2 (CHEK2) is frequently included in multigene panels. We describe the associated outcomes among carriers of CHEK2 pathogenic variants in young patients with symptomatic breast cancer. Participants (N = 2,344) in the Prospective Outcomes in Sporadic Versus Hereditary Breast Cancer study had a diagnosis of primary invasive breast cancer at age ≤ 40 years. Summary statistics were used to compare tumor characteristics among CHEK2+ carriers with those who were CHEK2-. Kaplan-Meier curves were used to demonstrate overall survival (OS) and distant disease-free survival. Overall, 53 of the 2,344 participants (2.3%) had a pathogenic CHEK2 variant. CHEK2+-associated tumors were significantly more likely to be grade 2, estrogen receptor and progesterone receptor-positive compared with CHEK2- tumors (grade 2, n = 28 of 52 [53.8%] v n = 803 of 2,229 [36.0%]; P = .029). CHEK2-associated tumors were significantly more likely to have nodal involvement (N1, n = 37 of 53 [69.8%] v 1,169 of 2,253 [51.9%]; P = .0098) and demonstrated a trend toward multifocality. A higher proportion of participants with CHEK2+ variants with invasive breast cancer were obese than were those with CHEK2- variant (28.3% v 18.8%; P = .039). Univariate and multivariable analyses revealed that OS and distant disease-free survival were significantly worse in CHEK2+ versus CHEK2- carriers (OS hazard ratio, 1.58; 95% CI, 1.01 to 2.48; P = .043). This work highlights the adverse prognosis associated with breast cancer in carriers of CHEK2 pathogenic variants. It also identifies a potential association among obesity, family history, and breast cancer risk in young CHEK2 gene carriers.

Abstract PR02: Mutations in RABL3 alter KRAS prenylation and are associated with hereditary pancreatic cancer

Abstract Beginning with discovery of a new genetic cause of familial pancreatic ductal adenocarcinoma (PDAC), this work uncovers a mechanism for regulating KRAS intracellular trafficking with implications for hereditary cancer, sporadic cancer, and RASopathy syndromes. PDAC is one of the deadliest solid cancers, with limited treatment options despite intensive research efforts. Familial predisposition to PDAC is thought to occur in ~10% of cases, but causative genes have not been identified in most of these families. Uncovering the genetic basis for PDAC susceptibility has immediate prognostic implications for families and can provide precious mechanistic clues to PDAC pathogenesis. Here, we perform whole-genome sequence analysis in a family with five cases of PDAC and identify a germline nonsense mutation in the member of RAS oncogene family-like 3 (RABL3) gene that has never before been directly associated with hereditary cancer. The truncated mutant allele (RABL3_p.Ser36*) co-segregates with cancer occurrence. To evaluate the contribution of the RABL3 mutant allele in hereditary cancer, we generated rabl3 heterozygous mutant zebrafish and found increased susceptibility to cancer formation in two independent cancer models. Complementary unbiased approaches implicate RABL3 in RAS pathway regulation. RNA-Seq and genome-set enrichment analysis of juvenile rabl3 mutants reveals a KRAS upregulation signature. Furthermore, affinity-purification mass spectrometry for proteins associated with RABL3 or RABL3_p.Ser36* identifies Rap1 GTPase-GDP Dissociation Stimulator 1 (RAP1GDS1, SmgGDS), a chaperone that regulates prenylation of RAS GTPases. Indeed, in vitro studies demonstrate that RABL3_p.Ser36* accelerates KRAS prenylation, and this impact is lost in the absence of H/N/KRAS proteins. Whereas heterozygous rabl3 mutant zebrafish exhibit cancer predisposition, homozygous rabl3 mutant zebrafish develop severe craniofacial, skeletal, and growth defects consistent with human RASopathies, and these defects are partially rescued with the MEK inhibitor trametinib. Finally, we identify additional germline mutations in RABL3 that impact RAS activity in vivo and have a significant burden in a cohort of patients with developmental disorders, suggesting a role in undiagnosed RASopathies. Moreover, RABL3 is upregulated in multiple human PDAC cell lines and knockdown abrogates proliferation, consistent with a broader role for RABL3 in PDAC. The discovered causative RABL3 germline mutation provides new diagnostic opportunities for genetic testing in other cancer families and uncovers an alternative mechanism for dysregulated RAS signaling in development and cancer. This abstract is also being presented as Poster A12. Citation Format: Sahar Nissim, Ignaty Leshchiner, Joseph Mancias, Matthew Greenblatt, Ophélia Maertens, Christopher Cassa, Jill Rosenfeld, Andrew Cox, John Hedgepeth, Julia Wucherpfennig, Andrew Kim, Jake Henderson, Patrick Gonyo, Anthony Brandt, Ellen Lorimer, Bethany Unger, Gad Getz, Shamil Sunyaev, Wade Harper, Karen Cichowski, Alec Kimmelman, Yariv Houvras, Sapna Syngal, Carol Williams, Wolfram Goessling. Mutations in RABL3 alter KRAS prenylation and are associated with hereditary pancreatic cancer [abstract]. In: Proceedings of the AACR Special Conference on Targeting RAS-Driven Cancers; 2018 Dec 9-12; San Diego, CA. Philadelphia (PA): AACR; Mol Cancer Res 2020;18(5_Suppl):Abstract nr PR02.

Loss of DNA mismatch repair proteins in prostate cancer.

Recent studies have suggested an increased risk of prostate cancer in men with Lynch syndrome driven by germline mutations in mismatch repair (MMR) genes. However, the incidence and clinical implication of MMR deficiency in sporadic prostate cancers remain poorly understood. We immunohistochemically stained for MLH1, MSH2, MSH6, and PMS2 in a set of tissue microarray consisting of 220 radical prostatectomy specimens and evaluated the relationship between loss of their expression and available clinicopathological features. MLH1, MSH2, MSH6, and PMS2 were lost in 2 (0.9%), 6 (2.7%), 37 (16.8%), and 27 (12.3%) prostate cancers, respectively. Loss of at least 1 MMR protein was identified in 50 (22.7%) cases. There were no statistically significant associations between MMR deficiency and patient age, family history of prostate cancer, Gleason score, or pT/pN stage. Nonetheless, the levels of preoperative prostate-specific antigen (PSA) were significantly (P = .015) higher in patients with MMR deficiency (mean ± SD: 9.12 ± 9.01 ng/mL) than in those without abnormal MMR (5.76 ± 3.17 ng/mL). There were 15 (6.8%) cases showing loss of at least 2 MMR proteins, which was not significantly associated with PSA level or tumor grade/stage. Additionally, 5 and 2 cases showed losses of at least 3 MMR proteins and all 4 proteins, respectively. Kaplan–Meier analysis revealed no significant associations between loss of MLH1 (P = .373), MSH2 (P = .348), MSH6 (P = .946), or PMS2 (P = .681), or at least 1 (P = .477), 2 (P = .486), or 3 (P = .352) MMR proteins and biochemical recurrence. Further analyses of the data on programmed death-ligand 1 (PD-L1) expression previously stained in the same set of tissue microarray demonstrated associations between loss of ≥2 MMR proteins and a higher rate of PD-L1 expression in cancer cells (17.2% vs 5.2%; P = .033) as well as between cases showing both loss of ≥1 MMR protein(s) and PD-L1 expression in tumor-infiltrating immune cells vs a higher risk of biochemical recurrence (P = .045). MMR protein loss was seen in a subset of prostate cancers. Interestingly, it was associated with significantly higher levels of PSA. Moreover, immunohistochemical detection of MMR proteins together with other proteins, such as PD-L1, might be helpful in predicting tumor recurrence following radical prostatectomy.

Abstract IA06: Colon cancer: Microbes and communities in microbiome translation

Abstract Intensive efforts are under way to understand how the colon microbiome contributes to the pathogenesis of colorectal cancer (CRC) and to determine if and how the microbiome can be utilized in the prevention and/or therapy of CRC. Both single microbes and microbial communities are proposed as contributors to human CRC. Among single microbes, attention to date has focused on enterotoxigenic Bacteroides fragilis (ETBF), (pks+) Escherichia coli, and Fusobacterium spp., although other candidates are emerging. Among communities, one aspect has been the potential contribution of mucus-invasive, dense mucosal microbial communities termed biofilms to CRC disease pathogenesis. This talk will review select concepts within ETBF’s and biofilm contribution to colon carcinogenesis. While ETBF exposure is common, the risk of colon carcinogenesis in an individual is unknown but potentially influenced by colonization state, B. fragilis toxin isotype secreted by ETBF, colon site, and the underlying genomic state of the colonic epithelial cells. With respect to colon biofilms, about 50% of human sporadic colon cancer, particularly in the right colon, display polymicrobial biofilms with marked tumor infiltration with bacteria whereas ~15% of normal colonoscopy biopsies also reveal polymicrobial biofilms. These polymicrobial biofilms are typically composed of Bacteroidetes and Lachnospiraceae with a subset of tumors, but not biopsies, also displaying Fusobacterium. Further, samples from biofilm-positive human colon cancers induce assembly of biofilms in the distal germ-free mouse colon within a week following inoculation and are procarcinogenic (JCI 129:1699, 2019). One of the common hereditary human colon cancers (familial adenomatous polyposis; APC+/−) also displays biofilms but dominated by two bacteria, (pks+) E. coli and ETBF. A mouse model of (pks+) E. coli and ETBF cocolonization exhibited accelerated tumor formation and mortality when cocolonized with the cancer-inducing bacteria, potentially by fostering increased microbial adherence, IL-17, changes in gene expression, and enhanced colonic epithelial cell DNA damage (Science 2018;359:592-97). Current directions of translational research will be presented. Citation Format: Cynthia L. Sears. Colon cancer: Microbes and communities in microbiome translation [abstract]. In: Proceedings of the AACR Special Conference on the Microbiome, Viruses, and Cancer; 2020 Feb 21-24; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2020;80(8 Suppl):Abstract nr IA06.

IMPDH inhibitors for antitumor therapy in tuberous sclerosis complex.

Recent studies in distinct preclinical tumor models have established the nucleotide synthesis enzyme inosine-5'-monophosphate dehydrogenase (IMPDH) as a viable target for antitumor therapy. IMPDH inhibitors have been used clinically for decades as safe and effective immunosuppressants. However, the potential to repurpose these pharmacological agents for antitumor therapy requires further investigation, including direct comparisons of available compounds. Therefore, we tested structurally distinct IMPDH inhibitors in multiple cell and mouse tumor models of the genetic tumor syndrome tuberous sclerosis complex (TSC). TSC-associated tumors are driven by uncontrolled activation of the growth-promoting protein kinase complex mechanistic target of rapamycin (mTOR) complex 1 (mTORC1), which is also aberrantly activated in the majority of sporadic cancers. Despite eliciting similar immunosuppressive effects, the IMPDH inhibitor mizoribine, used clinically throughout Asia, demonstrated far superior antitumor activity compared with the FDA-approved IMPDH inhibitor mycophenolate mofetil (or CellCept, a prodrug of mycophenolic acid). When compared directly to the mTOR inhibitor rapamycin, mizoribine treatment provided a more durable antitumor response associated with tumor cell death. These results provide preclinical support for repurposing mizoribine, over other IMPDH inhibitors, as an alternative to mTOR inhibitors for the treatment of TSC-associated tumors and possibly other tumors featuring uncontrolled mTORC1 activity.

Abstract A25: Hectd3 protects against colitis and colon cancer development through maintenance of homeostatic immune environment in the gut

Abstract Colorectal cancer (CRC) remains one of the most common and deadliest malignancies in USA, including in Florida. CRC includes hereditary, sporadic, and colitis-associated cancer (CAC). CAC often shows rapid progression, poor response to treatment, and high mortality. In CAC, tumors are formed in the context of chronic inflammation, but ultimately the immune populations in colonic tumors acquire a suppressive phenotype. Among such populations, myeloid-derived suppressive cells (MDSCs), consisting of polymorphonuclear (PMN)-MDSCs and monocytic (M)-MDSCs, accumulate in the tumors and promote a tumor-suppressive microenvironment, together with tumor-associated macrophages. Numerous questions remain unanswered in regard to the biology and regulation of myeloid-suppressive populations in CAC. We found that the levels of the ubiquitin ligase Hectd3 were reduced in human inflamed ulcerative colitis (UC) tissues and in colonic tumors versus healthy matched colonic tissues. Hectd3 KO mice developed more severe dextran sodium sulfate (DSS)-induced colitis and larger and more numerous colonic tumors in the azoxymethane (AOM)/DSS model of CAC. Bone marrow chimera experiments demonstrated that both the hematopoietic and nonhematopoietic compartments play roles in the phenotype, in DSS colitis and in AOM/DSS CAC model. During DSS-induced colitis we found that genes for several proinflammatory cytokines were upregulated in the colons of Hectd3 KO mice, including IL6, IL11 and G-CSF, as well for Lipocalin-2, associated with inflammation. However, in the colonic tumors of Hectd3 KO mice, the CD11b+ CD11c- myeloid cells were elevated and showed increased Arginase 1 and iNOS levels and frequencies, suggestive of a suppressive phenotype. We hypothesize that absence of Hectd3 promotes a highly inflammatory phenotype in the colon, and further an immune-suppressive phenotype in the colonic tumors through regulation of specific signaling pathways in myeloid populations. Citation Format: Ashley Zuniga, Upasana Parthasarath, Jonathan Cho, Theodore Drashansky, Eric Helm, Kyle Lorentsen, Zhen He, Christian Jobin, Dorina Avram. Hectd3 protects against colitis and colon cancer development through maintenance of homeostatic immune environment in the gut [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2018 Nov 27-30; Miami Beach, FL. Philadelphia (PA): AACR; Cancer Immunol Res 2020;8(4 Suppl):Abstract nr A25.

Differential microRNA expression profiles associated with microsatellite status reveal possible epigenetic regulation of microsatellite instability in gastric adenocarcinoma.

BackgroundAlthough microsatellite instability (MSI) is a powerful predictive biomarker for the efficacy of immunotherapy, the mechanism of MSI in sporadic gastrointestinal cancer is not fully understood. However, epigenetics, particularly microRNAs, has been suggested as one of the main regulators that contribute to the MSI formation.MethodsWe used microRNA expression data of 386 gastric adenocarcinoma samples from The Cancer Genome Atlas (TCGA) database to identify differential microRNA expression profiles by different MSI status. We also obtained putative common target genes of the top differential microRNAs with miRanda online tools, and we analyzed these data by Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes pathway enrichment (KEGG).ResultsWe found that 56 and 67 gastric adenocarcinoma samples were positive for low and high MSI, respectively, and that a high MSI status was associated with age, sex and subregion (P=0.049, 0.014 and 0.007, respectively). In the 67 samples with a high MSI status, expression levels of 14 microRNAs were upregulated but five microRNAs were downregulated as assessed by the fold change (FC), compared with that of the 56 samples with a low MSI status (P<0.05, |FC| >2). Further analysis suggested that the expression of miR-210-3p, miR-582-3p, miR-30a-3p and miR-105-5p predicted a high MSI status (P=4.93×10−10, 5.63×10−10, 3.23×10−9 and 7.64×10−4, respectively). Regulation of the transcription pathways ranked the top of lists from both GO and KEGG analyses, and these microRNAs might regulate DNA damage-repair genes that were also associated with a high MSI status.ConclusionsMiR-30a-3p and miR-105-5p are potential biomarkers for the MSI-H gastric adenocarcinoma, possibly by altering expression of DNA damage-repair genes.

MicroRNA-200 family governs ovarian inclusion cyst formation and mode of ovarian cancer spread.

Epidemiologic and histopathologic findings and the laying hen model support the long-standing incessant ovulation hypothesis and cortical inclusion cyst involvement in sporadic ovarian cancer development. MicroRNA-200 (miR-200) family is highly expressed in ovarian cancer. Herewith, we show that ovarian surface epithelial (OSE) cells with ectopic miR-200 expression formed stabilized cysts in three-dimensional (3D) organotypic culture with E-cadherin fragment expression and steroid hormone pathway activation, whereas ovarian cancer 3D cultures with miR-200 knockdown showed elevated TGF-β expression, mitotic spindle disorientation, increased lumenization, disruption of ROCK-mediated myosin II phosphorylation, and SRC signaling, which led to histotype-dependent loss of collective movement in tumor spread. Gene expression profiling revealed that epithelial-mesenchymal transition and hypoxia were the top enriched gene sets regulated by miR-200 in both OSE and ovarian cancer cells. The molecular changes uncovered by the in vitro studies were verified in both human and laying hen ovarian cysts and tumor specimens. As miR-200 is also essential for ovulation, our results of estrogen pathway activation in miR-200-expressing OSE cells add another intriguing link between incessant ovulation and ovarian carcinogenesis.

An immune-centric exploration of BRCA1 and BRCA2 germline mutation related breast and ovarian cancers

BackgroundBRCA1/2 germline mutation related cancers are candidates for new immune therapeutic interventions. This study was a hypothesis generating exploration of genomic data collected at diagnosis for 19 patients. The prominent tumor mutation burden (TMB) in hereditary breast and ovarian cancers in this cohort was not correlated with high global immune activity in their microenvironments. More information is needed about the relationship between genomic instability, phenotypes and immune microenvironments of these hereditary tumors in order to find appropriate markers of immune activity and the most effective anticancer immune strategies.MethodsMining and statistical analyses of the original DNA and RNA sequencing data and The Cancer Genome Atlas data were performed. To interpret the data, we have used published literature and web available resources such as Gene Ontology, The Cancer immunome Atlas and the Cancer Research Institute iAtlas.ResultsWe found that BRCA1/2 germline related breast and ovarian cancers do not represent a unique phenotypic identity, but they express a range of phenotypes similar to sporadic cancers. All breast and ovarian BRCA1/2 related tumors are characterized by high homologous recombination deficiency (HRD) and low aneuploidy. Interestingly, all sporadic high grade serous ovarian cancers (HGSOC) and most of the subtypes of triple negative breast cancers (TNBC) also express a high degree of HRD.ConclusionsTMB is not associated with the magnitude of the immune response in hereditary BRCA1/2 related breast and ovarian cancers or in sporadic TNBC and sporadic HGSOC. Hereditary tumors express phenotypes as heterogenous as sporadic tumors with various degree of “BRCAness” and various characteristics of the immune microenvironments. The subtyping criteria developed for sporadic tumors can be applied for the classification of hereditary tumors and possibly also characterization of their immune microenvironment. A high HRD score may be a good candidate biomarker for response to platinum, and potentially PARP-inhibition.Trial registrationPhase I Study of the Oral PI3kinase Inhibitor BKM120 or BYL719 and the Oral PARP Inhibitor Olaparib in Patients With Recurrent TNBC or HGSOC (NCT01623349), first posted on June 20, 2012. The design and the outcome of the clinical trial is not in the scope of this study.

Clinical Outcomes in Patients With Colon Cancer With Microsatellite Instability of Sporadic or Familial Origin Treated With Adjuvant FOLFOX With or Without Cetuximab: A Pooled Analysis of the PETACC8 and N0147 Trials.

The microsatellite instability (MSI) or deficient mismatch repair (dMMR) phenotype is usually regarded as a single biologic entity, given the absence of comparative analyses regarding prognosis and response to chemotherapy between sporadic and familial dMMR cancers. Patients with stage III colon cancers were randomly assigned to FOLFOX (leucovorin, fluorouracil, and oxaliplatin) with or without cetuximab in 2 large adjuvant phase III trials (N = 5,577). Among patients with MSI and KRAS exon 2 wild-type (WT) tumors, the prognostic and predictive impacts of sporadic versus familial dMMR cancers and BRAF V600E mutational status were determined. Multivariable Cox proportional hazards models were used to assess disease-free survival (DFS) by treatment arm, adjusting for age, sex, tumor grade, Eastern Cooperative Oncology Group performance status, pT/pN stage, and primary tumor location. Among patients with MSI status with complete data for dMMR mechanism analysis (n = 354), 255 (72%) had sporadic (BRAF mutation and/or MLH1 methylation) and 99 (28%) had familial tumors (BRAF WT and unmethylated MLH1 or loss of MSH2/MSH6/PMS2 protein expression). A large proportion of dMMR sporadic tumors were mutated for BRAF (n = 200). In patients treated with FOLFOX, DFS did not differ statistically by dMMR mechanism, whereas in patients treated with FOLFOX plus cetuximab, those with sporadic tumors had worse DFS than those with familial cancers (multivariable hazard ratio, 2.69; 95% CI, 1.02 to 7.08; P = .04). Considering the predictive utility, the interaction between treatment and dMMR mechanism was significant (P = .03). Furthermore, a nonsignificant trend toward a deleterious effect of adding cetuximab to FOLFOX was observed in patients with BRAF-mutant but not BRAF WT tumors. The addition of cetuximab to adjuvant FOLFOX was associated with shorter DFS in patients with sporadic dMMR colon cancer. Additional studies are needed to validate these results in metastatic disease.

A31 ALTERED SMALL INTESTINAL EPITHELIAL HOMEOSTASIS AND CELL FATE DECISION UPON LOSS OF TRP53 IN KRT15+ INTESTINAL STEM CELLS

Abstract Background Intestinal homeostasis is mainly maintained by two groups of stem cells: Lgr5+ stem cells and reserve stem cells. Recently, we reported that Krt15+ cells are present in small intestinal and colon epithelia, and harbor self-renewal, multipotent and regenerative capacities. Initiation of sporadic colorectal cancer has been described in Krt15+ stem cells, Lgr5+ stem cells and reserve stem cells following the loss of Apc. While these intestinal stem cell (ISC) populations can act as tumor-initiating cells in sporadic colon cancer, little is known about the cell-of-origin of colitis-associated colon cancer. TP53 alteration is reported as an early event in colitis-associated colon cancer cases. Therefore, we hypothesize that Trp53 loss specifically in Krt15+ stem cells will perturb the epithelial homeostasis and lead to tumor formation Aims Identify if Krt15+ cells may act as the cell-of-origin in colitis-associated colorectal cancer. Methods To induce Trp53 loss specifically in Krt15+ cells, we generated Krt15-CrePR1;Trp53fl/fl (Krt15△Trp53) mice, induced Cre recombination by injecting RU486 (PR agonist) and euthanized the mice after 12 months following recombination. Histological analysis was performed on small intestinal tissues. Results Results: Trp53 loss in Krt15+ cells severely perturbed small intestinal morphology. Increased crypt (proliferative compartment) length correlated with no proliferation changes surprisingly but higher number of Paneth cells and abnormal presence of goblet cells. Interestingly, we also observed the presence of cells expressing both Paneth and goblet cells markers suggesting a deregulation of secretory cell fate decision. Decreased expression of Hes1 and increased β-catenin nuclear expression in the small intestinal crypt of Krt15△Trp53 mice suggest altered Notch and Wnt signaling. Furthermore, villi (differentiated compartment) were significantly wider and shorter, and showed accumulation of activated fibroblasts. Finally, we observed inflammatory lesions as well as adenomas in the small intestine of Krt15△Trp53 mice which remain to be further characterized Conclusions Conclusion: In summary, Trp53 loss specifically in Krt15+ cells impaired cell fate decision, induced inflammation and initiated tumor formation. Overall, these results suggest that Krt15+ cells could act as the cell-of-origin of colitis-associated colon cancer. Funding Agencies Cancer Research Society, CRC Tier 2