Genomic characterization of metastatic breast cancers.

Metastasis is the main cause of death for patients with breast cancer. Many studies have characterized the genomic landscape of breast cancer during its early stages. However, there is evidence that genomic alterations are acquired during the evolution of cancers from their early to late stages, and that the genomic landscape of early cancers is not representative of that of lethal cancers1-7. Here we investigated the landscape of somatic alterations in 617 metastatic breast cancers. Nine driver genes (TP53, ESR1, GATA3, KMT2C, NCOR1, AKT1, NF1, RIC8A and RB1) were more frequently mutated in metastatic breast cancers that expressed hormone receptors (oestrogen and/or progesterone receptors; HR+) but did not have high levels of HER2 (HER2-; n = 381), when compared to early breast cancers from The Cancer Genome Atlas. In addition, 18 amplicons were more frequently observed in HR+/HER2- metastatic breast cancers. These cancers showed an increase in mutational signatures S2, S3, S10, S13 and S17. Among the gene alterations that were enriched in HR+/HER2- metastatic breast cancers, mutations in TP53, RB1 and NF1, together with S10, S13 and S17, were associated with poor outcome. Metastatic triple-negative breast cancers showed an increase in the frequency of somatic biallelic loss-of-function mutations in genes related to homologous recombination DNA repair, compared to early triple-negative breast cancers (7% versus 2%). Finally, metastatic breast cancers showed an increase in mutational burden and clonal diversity compared to early breast cancers. Thus, the genomic landscape of metastatic breast cancer is enriched in clinically relevant genomic alterations and is more complex than that of early breast cancer. The identification of genomic alterations associated with poor outcome will allow earlier and better selection of patients who require the use of treatments that are still in clinical trials. The genetic complexity observed in advanced breast cancer suggests that such treatments should be introduced as early as possible in the disease course.

Author Correction: Genomic characterization of metastatic breast cancers.

An Amendment to this paper has been published and can be accessed via a link at the top of the paper.

Potential value of ctDNA monitoring in metastatic HR + /HER2 - breast cancer: longitudinal ctDNA analysis in the phase Ib MONALEESASIA trial.

BACKGROUND: There is increasing interest in the use of liquid biopsies, but data on longitudinal analyses of circulating tumor DNA (ctDNA) remain relatively limited. Here, we report a longitudinal ctDNA analysis of MONALEESASIA, a phase Ib trial evaluating the efficacy and safety of ribociclib plus endocrine therapy (ET) in Asian patients with hormone receptor-positive, human epidermal growth factor receptor-2-negative advanced breast cancer. METHODS: MONALEESASIA enrolled premenopausal and postmenopausal Japanese and postmenopausal non-Japanese Asian patients. All patients received ribociclib with ET (letrozole, fulvestrant, or tamoxifen with goserelin). ctDNA was analyzed using a targeted next-generation sequencing panel of 572 cancer-related genes and correlated by best overall response (BOR). RESULTS: Five hundred seventy-four cell-free DNA samples from 87 patients were tested. The most frequently altered genes at baseline included PIK3CA (29%) and TP53 (22%). Treatment with ribociclib plus ET decreased ctDNA in most patients at the first on-treatment time point, regardless of dose or ET partner. Patients with partial response and stable disease had lower ctDNA at baseline that remained low until data cutoff if no progressive disease occurred. Most patients with progressive disease as the best response had higher ctDNA at baseline that remained high at the end of treatment. For patients with partial response and stable disease with subsequent progression, ctDNA increased towards the end of treatment in most patients, with a median lead time of 83 days (14-309 days). In some patients with BOR of partial response who experienced disease progression later, specific gene alterations and total ctDNA fraction increased; this was sometimes observed concurrently with the development of new lesions without a change in target lesion size. Patients with alterations in PIK3CA and TP53 at baseline had shorter median progression-free survival compared with patients with wild-type PIK3CA and TP53, 12.7 and 7.3 months vs 19.2 and 19.4 months, respectively (P = .016 and P = .0001, respectively). CONCLUSIONS: Higher ctDNA levels and PIK3CA and TP53 alterations detected at baseline were associated with inferior outcomes. On-treatment ctDNA levels were associated with different patterns based on BOR. Longitudinal tracking of ctDNA may be useful for monitoring tumor status and detection of alterations with treatment implications. TRIAL REGISTRATION: ClinicalTrials.gov NCT02333370 . Registered on January 7, 2015.

Targeting activated PI3K/mTOR signaling overcomes acquired resistance to CDK4/6-based therapies in preclinical models of hormone receptor-positive breast cancer.

BACKGROUND: Combined targeting of CDK4/6 and ER is now the standard of care for patients with advanced ER+/HER2- breast cancer. However, acquired resistance to these therapies frequently leads to disease progression. As such, it is critical to identify the mechanisms by which resistance to CDK4/6-based therapies is acquired and also identify therapeutic strategies to overcome resistance. METHODS: In this study, we developed and characterized multiple in vitro and in vivo models of acquired resistance to CDK4/6-based therapies. Resistant models were screened by reverse phase protein array (RPPA) for cell signaling changes that are activated in resistance. RESULTS: We show that either a direct loss of Rb or loss of dependence on Rb signaling confers cross-resistance to inhibitors of CDK4/6, while PI3K/mTOR signaling remains activated. Treatment with the p110α-selective PI3K inhibitor, alpelisib (BYL719), completely blocked the progression of acquired CDK4/6 inhibitor-resistant xenografts in the absence of continued CDK4/6 inhibitor treatment in models of both PIK3CA mutant and wild-type ER+/HER2- breast cancer. Triple combination therapy against PI3K:CDK4/6:ER prevented and/or delayed the onset of resistance in treatment-naive ER+/HER2- breast cancer models. CONCLUSIONS: These data support the clinical investigation of p110α-selective inhibitors of PI3K, such as alpelisib, in patients with ER+/HER2- breast cancer who have progressed on CDK4/6:ER-based therapies. Our data also support the investigation of PI3K:CDK4/6:ER triple combination therapy to prevent the onset of resistance to the combination of endocrine therapy plus CDK4/6 inhibition.

PRT543, a protein arginine methyltransferase 5 inhibitor, in patients with advanced adenoid cystic carcinoma: An open-label, phase I dose-expansion study.

OBJECTIVES: Currently, no systemic treatments are approved for patients with recurrent and/or metastatic (R/M) adenoid cystic carcinoma (ACC). PRT543, a protein arginine methyltransferase 5 inhibitor that downregulates NOTCH1 and MYB signalling in tumours, is a potential candidate for R/M ACC treatment. We report the safety, tolerability and preliminary efficacy of PRT543 in a dose-expansion cohort of patients with R/M ACC. MATERIALS AND METHODS: This phase I multicentre, open-label, sequential-cohort, dose-escalation and dose-expansion study (NCT03886831) enrolled patients with advanced solid tumours and select haematologic malignancies. Dose-escalation study design and results were reported previously. In the dose expansion, patients with R/M ACC received recommended phase II doses of 35 or 45 mg PRT543 orally on days 1-5 of each week. Primary objectives were to establish the safety and tolerability of PRT543. Secondary objectives included efficacy. RESULTS: Between February 2019 and May 2022, 56 patients with ACC were enrolled across 23 US sites and received either 35 mg (n = 28) or 45 mg (n = 28) of PRT543. Overall, 23% of patients experienced a grade 3 treatment-related adverse event, most commonly anaemia (16%) and thrombocytopaenia (9%). No grade 4/5 treatment-emergent adverse events were reported. Median progression-free survival was 5.9 months (95% CI: 3.8-8.3). The clinical benefit rate was 57% (95% CI: 43-70). Overall response rate (per Response Evaluation Criteria in Solid Tumours v1.1) was 2%, with 70% of patients having stable disease. CONCLUSION: In this analysis, PRT543 was tolerable, and the observed efficacy was limited in patients with R/M ACC.

Targeting polyamines and inflammation for cancer prevention.

Increased polyamine synthesis and inflammation have long been associated with intraepithelial neoplasia, which are risk factors for cancer development in humans. Targeting polyamine metabolism (by use of polyamine synthesis inhibitors or polyamine catabolism activators) and inflammation (by use of nonsteroidal anti-inflammatory drugs) has been studied for many cancers, including colon, prostate, and skin. Genetic epidemiology results indicate that a genetic variant associated with the expression of a polyamine biosynthetic gene is associated with risk of colon and prostate cancers. A clinical trial of difluoromethylornithine (DFMO), a selective inhibitor of polyamine synthesis, showed that the 1 year treatment duration reduced prostate volume and serum prostate-specific antigen doubling time in men with a family history of prostate cancer. A second, clinical trial of DFMO in combination with sulindac, a NSAID in patients with prior colon polyps found that the 3-year treatment was associated with a 70% reduction of all, and over a 90% reduction of advanced and/or multiple metachronous colon adenomas. In this chapter, we discuss that similar combination prevention strategies of targeting polyamines and inflammation can be effective in reducing risk factors associated with the development of human cancers.

Correlative Biomarker Analysis of Intrinsic Subtypes and Efficacy Across the MONALEESA Phase III Studies.

PURPOSE: The prognostic and predictive value of intrinsic subtypes in hormone receptor-positive, human epidermal growth factor receptor 2-negative advanced breast cancer treated with endocrine therapy and ribociclib (RIB) is currently unknown. We evaluated the association of intrinsic subtypes with progression-free survival (PFS) in the MONALEESA trials. METHODS: A retrospective and exploratory PAM50-based analysis of tumor samples from the phase III MONALEESA-2, MONALEESA-3, and MONALEESA-7 trials was undertaken. The prognostic relationship of PAM50-based subtypes with PFS and risk of disease progression by subtype and treatment were evaluated using a multivariable Cox proportional hazards model, adjusting for age, prior chemotherapy, performance status, visceral disease, bone-only metastases, histological grade, number of metastatic sites, prior endocrine therapy, and de novo metastatic disease. RESULTS: Overall, 1,160 tumors from the RIB (n = 672) and placebo (n = 488) cohorts were robustly profiled. Subtype distribution was luminal A (LumA), 46.7%; luminal B (LumB), 24.0%; normal-like, 14.0%; HER2-enriched (HER2E), 12.7%; and basal-like, 2.6% and was generally consistent across treatment arms and trials. The associations between subtypes and PFS were statistically significant in both arms (P < .001). The risks of disease progression for LumB, HER2E, and basal-like subtypes were 1.44, 2.31, and 3.96 times higher compared with those for LumA, respectively. All subtypes except basal-like demonstrated significant PFS benefit with RIB. HER2E (hazard ratio [HR], 0.39; P < .0001), LumB (HR, 0.52; P < .0001), LumA (HR, 0.63; P = .0007), and normal-like (HR, 0.47; P = .0005) subtypes derived benefit from RIB. Patients with basal-like subtype (n = 30) did not derive benefit from RIB (HR, 1.15; P = .77). CONCLUSION: In this retrospective exploratory analysis of hormone receptor-positive and human epidermal growth factor receptor 2-negative advanced breast cancer, each intrinsic subtype exhibited a consistent PFS benefit with RIB, except for basal-like.

Genomic Profiling of Premenopausal HR+ and HER2- Metastatic Breast Cancer by Circulating Tumor DNA and Association of Genetic Alterations With Therapeutic Response to Endocrine Therapy and Ribociclib.

PURPOSE: This analysis evaluated the genomic landscape of premenopausal patients with hormone receptor-positive and human epidermal growth factor receptor 2-negative advanced breast cancer and the association of genetic alterations with response to ribociclib in the phase III MONALEESA-7 trial. METHODS: Premenopausal patients were randomly assigned 1:1 to receive endocrine therapy plus ribociclib or placebo. Plasma collected at baseline was sequenced using targeted next-generation sequencing for approximately 600 relevant cancer genes. The association of circulating tumor DNA alterations with progression-free survival (PFS) was evaluated to identify biomarkers of response and resistance to ribociclib. RESULTS: Baseline circulating tumor DNA was sequenced in 565 patients; 489 had evidence of ≥ 1 alteration. The most frequent alterations included PIK3CA (28%), TP53 (19%), CCND1 (10%), MYC (8%), GATA3 (8%), receptor tyrosine kinases (17%), and the Chr8p11.23 locus (12%). A treatment benefit of ribociclib was seen with wild-type (hazard ratio [HR] 0.45 [95% CI, 0.33 to 0.62]) and altered (HR 0.57 [95% CI, 0.36 to 0.9]) PIK3CA. Overall, patients with altered CCND1 had shorter PFS regardless of treatment, suggesting CCND1 as a potential prognostic biomarker. Benefit with ribociclib was seen in patients with altered (HR 0.21 [95% CI, 0.08 to 0.54]) or wild-type (HR 0.52 [95% CI, 0.39 to 0.68]) CCND1, but greater benefit was observed with altered, suggesting predictive potential of CCND1. Alterations in TP53, MYC, Chr8p11.23 locus, and receptor tyrosine kinases were associated with worse PFS, but ribociclib benefit was independent of alteration status. CONCLUSION: In this study-to our knowledge, the first large study of premenopausal patients with hormone receptor-positive and human epidermal growth factor receptor 2-negative advanced breast cancer-multiple genomic alterations were associated with poor outcome. A PFS benefit of ribociclib was observed regardless of gene alteration status, although in this exploratory analysis, a magnitude of benefits varied by alteration.

A Phase II Randomized Study of Neoadjuvant Letrozole Plus Alpelisib for Hormone Receptor-Positive, Human Epidermal Growth Factor Receptor 2-Negative Breast Cancer (NEO-ORB).

PURPOSE: Addition of alpelisib to fulvestrant significantly extended progression-free survival in PIK3CA-mutant, hormone receptor-positive (HR+) advanced/metastatic breast cancer in the phase III SOLAR-1 study. The combination of alpelisib and letrozole also had promising activity in phase I studies of HR+ advanced/metastatic breast cancer. NEO-ORB aimed to determine whether addition of alpelisib to letrozole could increase response rates in the neoadjuvant setting.Patients and Methods: Postmenopausal women with HR+, human epidermal growth factor receptor 2-negative, T1c-T3 breast cancer were assigned to the PIK3CA-wild-type or PIK3CA-mutant cohort according to their tumor PIK3CA status, and randomized (1:1) to 2.5 mg/day letrozole with 300 mg/day alpelisib or placebo for 24 weeks. Primary endpoints were objective response rate (ORR) and pathologic complete response (pCR) rate for both PIK3CA cohorts. RESULTS: In total, 257 patients were assigned to letrozole plus alpelisib (131 patients) or placebo (126 patients). Grade ≥3 adverse events (≥5% of patients) in the alpelisib arm were hyperglycemia (27%), rash (12%), and maculo-papular rash (8%). The primary objective was not met; ORR in the alpelisib versus placebo arm was 43% versus 45% and 63% versus 61% in the PIK3CA-mutant and wild-type cohorts, respectively. pCR rates were low in all groups. Decreases in Ki-67 were similar across treatment arms and cohorts. In PIK3CA-mutant tumors, alpelisib plus letrozole treatment induced a greater decrease in phosphorylated AKT versus placebo plus letrozole. CONCLUSIONS: In contrast to initial results in advanced/metastatic disease, addition of alpelisib to 24-week neoadjuvant letrozole treatment did not improve response in patients with HR+ early breast cancer.

Tumor necrosis factor-alpha increases reactive oxygen species by inducing spermine oxidase in human lung epithelial cells: a potential mechanism for inflammation-induced carcinogenesis.

Inflammation has been implicated in the development of many human epithelial cancers, including those of the stomach, lung, colon, and prostate. Tumor necrosis factor-alpha (TNF-alpha) is a potent pleiotropic, proinflammatory cytokine produced by many cells in response to injury and inflammation. Here, we show that TNF-alpha exposure results in increased production of reactive oxygen species (ROS), with a concomitant increase in the production of 8-oxo-deoxyguanosine, a marker for oxidative DNA damage, in human lung bronchial epithelial cells. The source of the ROS in TNF-alpha-treated cells was determined by both pharmacologic and small interfering RNA (siRNA) strategies to be spermine oxidase (SMO/PAOh1). SMO/PAOh1 oxidizes spermine into spermidine, 3-aminopropanal, and H(2)O(2). Inhibition of TNF-alpha-induced SMO/PAOh1 activity with MDL 72,527 or with a targeted siRNA prevented ROS production and oxidative DNA damage. Further, similar induction in SMO/PAOh1 is observed with treatment of another inflammatory cytokine, interleukin-6. The data are consistent with a model that directly links inflammation and DNA damage through the production of H(2)O(2) by SMO/PAOh1. Further, these results suggest a common mechanism by which inflammation from multiple sources can lead to the mutagenic changes necessary for the development and progression of epithelial cancers.

Induction of spermidine/spermine N1-acetyltransferase (SSAT) by aspirin in Caco-2 colon cancer cells.

Epidemiological, experimental and clinical results suggest that aspirin and other NSAIDs (non-steroidal anti-inflammatory drugs) inhibit the development of colon cancer. It has been shown that the NSAID sulindac induces apoptosis and suppresses carcinogenesis, in part, by a mechanism leading to the transcriptional activation of the gene encoding SSAT (spermidine/spermine N1-acetyltransferase), a rate-limiting enzyme in polyamine catabolism. In the present study, we show that a variety of NSAIDs, including aspirin, sulindac, ibuprofen and indomethacin, can induce SSAT gene expression in Caco-2 cells. Aspirin, at physiological concentrations, can induce SSAT mRNA via transcriptional initiation mechanisms. This induction leads to increased SSAT protein levels and enzyme activity. Promoter deletion analysis of the 5' SSAT promoter-flanking region led to the identification of two NF-kappaB (nuclear factor kappaB) response elements. Electrophoretic mobility-shift assays showed binding of NF-kappaB complexes at these sequences after aspirin treatment. Aspirin treatment led to the activation of NF-kappaB signalling and increased binding at these NF-kappaB sites in the SSAT promoter, hence providing a potential mechanism for the induction of SSAT by aspirin in these cells. Aspirin-induced SSAT ultimately leads to a decrease in cellular polyamine content, which has been associated with decreased carcinogenesis. These results suggest that activation of SSAT by aspirin and different NSAIDs may be a common property of NSAIDs that plays an important role in their chemopreventive actions in colorectal cancer.

A Plasma-Based Protein Marker Panel for Colorectal Cancer Detection Identified by Multiplex Targeted Mass Spectrometry.

INTRODUCTION: Colorectal cancer (CRC) testing programs reduce mortality; however, approximately 40% of the recommended population who should undergo CRC testing does not. Early colon cancer detection in patient populations ineligible for testing, such as the elderly or those with significant comorbidities, could have clinical benefit. Despite many attempts to identify individual protein markers of this disease, little progress has been made. Targeted mass spectrometry, using multiple reaction monitoring (MRM) technology, enables the simultaneous assessment of groups of candidates for improved detection performance. MATERIALS AND METHODS: A multiplex assay was developed for 187 candidate marker proteins, using 337 peptides monitored through 674 simultaneously measured MRM transitions in a 30-minute liquid chromatography-mass spectrometry analysis of immunodepleted blood plasma. To evaluate the combined candidate marker performance, the present study used 274 individual patient blood plasma samples, 137 with biopsy-confirmed colorectal cancer and 137 age- and gender-matched controls. Using 2 well-matched platforms running 5 days each week, all 274 samples were analyzed in 52 days. RESULTS: Using one half of the data as a discovery set (69 disease cases and 69 control cases), the elastic net feature selection and random forest classifier assembly were used in cross-validation to identify a 15-transition classifier. The mean training receiver operating characteristic area under the curve was 0.82. After final classifier assembly using the entire discovery set, the 136-sample (68 disease cases and 68 control cases) validation set was evaluated. The validation area under the curve was 0.91. At the point of maximum accuracy (84%), the sensitivity was 87% and the specificity was 81%. CONCLUSION: These results have demonstrated the ability of simultaneous assessment of candidate marker proteins using high-multiplex, targeted-mass spectrometry to identify a subset group of CRC markers with significant and meaningful performance.

Tumor necrosis factor alpha induces spermidine/spermine N1-acetyltransferase through nuclear factor kappaB in non-small cell lung cancer cells.

Tumor necrosis factor alpha (TNFalpha) is a potent pleiotropic cytokine produced by many cells in response to inflammatory stress. The molecular mechanisms responsible for the multiple biological activities of TNFalpha are due to its ability to activate multiple signal transduction pathways, including nuclear factor kappaB (NFkappaB), which plays critical roles in cell proliferation and survival. TNFalpha displays both apoptotic and antiapoptotic properties, depending on the nature of the stimulus and the activation status of certain signaling pathways. Here we show that TNFalpha can lead to the induction of NFkappaB signaling with a concomitant increase in spermidine/spermine N(1)-acetyltransferase (SSAT) expression in A549 and H157 non-small cell lung cancer cells. Induction of SSAT, a stress-inducible gene that encodes a rate-limiting polyamine catabolic enzyme, leads to lower intracellular polyamine contents and has been associated with decreased cell growth and increased apoptosis. Stable overexpression of a mutant, dominant negative IkappaBalpha protein led to the suppression of SSAT induction by TNFalpha in these cells, thereby substantiating a role of NFkappaB in the induction of SSAT by TNFalpha. SSAT promoter deletion constructs led to the identification of three potential NFkappaB response elements in the SSAT gene. Electromobility shift assays, chromatin immunoprecipitation experiments and mutational studies confirmed that two of the three NFkappaB response elements play an important role in the regulation of SSAT in response to TNFalpha. The results of these studies indicate that a common mediator of inflammation can lead to the induction of SSAT expression by activating the NFkappaB signaling pathway in non-small cell lung cancer cells.

Suppression of polyamine catabolism by activated Ki-ras in human colon cancer cells.

An activated Ki-ras was expressed in the human colon adenocarcinoma cell line Caco-2 to study the effects of Ki-ras oncogene on polyamine metabolism during gastrointestinal tumorigenesis. Multiple clones selected for expression of the mutant Ki-ras transgene displayed a suppression of transcription of a key catabolic enzyme in polyamine catabolism spermidine/spermine N1-acetyltransferase (SSAT). Gene expression analysis, with cDNA microarrays, showed that Ki-ras transfected clones had decreased levels of expression, compared to mock transfected cells, of peroxisome proliferator-activated receptor gamma (PPARgamma), a member of the nuclear hormone receptor family and an important regulator of cell proliferation and differentiation. The activated Ki-ras suppressed SSAT expression by a mechanism involving the PPARgamma response element (PPRE) located at +48 bp relative to the transcription start site of the SSAT gene. Transient expression of the PPARgamma protein in Ki-ras expressing Caco-2 clones, or treatment with the PPARgamma ligand ciglitazone, led to an increase in the SSAT promoter activity. A MEK1/2 inhibitor PD98059 induced transcription of both PPARgamma and SSAT genes in the activated Ki-ras clones, suggesting that the mitogen-activated protein kinases (MAPKs) were involved in the regulation of SSAT expression by PPARgamma. We concluded that mutated Ki-ras suppressed SSAT via a transcriptional mechanism involving the PPARgamma signaling pathway.

Cyclooxygenase-independent induction of apoptosis by sulindac sulfone is mediated by polyamines in colon cancer.

Sulindac, a non-steroidal anti-inflammatory prodrug, is metabolized into pharmacologically active sulfide and sulfone derivatives. Sulindac sulfide, but not sulindac sulfone, inhibits cyclooxygenase (COX) enzyme activities, yet both derivatives have growth inhibitory effects on colon cancer cells. Microarray analysis was used to detect COX-independent effects of sulindac on gene expression in human colorectal cells. Spermidine/sperm-ine N1-acetyltransferase (SSAT) gene, which encodes a polyamine catabolic enzyme, was induced by clinically relevant sulindac sulfone concentrations. Northern blots confirmed increased SSAT RNA levels in these colon cancer cells. Deletion analysis and mutational studies were done to map the sulindac sulfone-dependent response sequences in the SSAT 5'-flanking sequences. This led us to the identification of two peroxisome proliferator-activated receptor (PPAR) response elements (PPREs) in the SSAT gene. PPRE-2, at +48 bases relative to the transcription start site, is required for the induction of SSAT by sulindac sulfone and is specifically bound by PPAR gamma in the Caco-2 cells as shown by transfection and gel shift experiments. PPRE-1, at-323 bases relative to the start site, is not required for the induction of SSAT by sulindac sulfone but can be bound by both PPAR delta and PPAR gamma. Sulindac sulfone reduced cellular polyamine contents in the absence but not in the presence of verapamil, an inhibitor of the export of monoacetyl diamines, inhibited cell proliferation and induced apoptosis. The induced apoptosis could be partially rescued by exogenous putrescine. These data suggest that apoptosis induced by sulindac sulfone is mediated, in part, by the COX-independent, PPAR-dependent transcriptional activation of SSAT, leading to reduced tissue polyamine contents in human colon cancer cells.

Pronounced reduction in adenoma recurrence associated with aspirin use and a polymorphism in the ornithine decarboxylase gene.

Most sporadic colon adenomas acquire mutations in the adenomatous polyposis coli gene (APC) and show defects in APC-dependent signaling. APC influences the expression of several genes, including the c-myc oncogene and its antagonist Mad1. Ornithine decarboxylase (ODC), the first enzyme in polyamine synthesis, is a transcriptional target of c-myc and a modifier of APC-dependent tumorigenesis. A single-nucleotide polymorphism exists in intron 1 of the human ODC gene, which lies between two myc-binding domains. This region is known to affect ODC transcription, but no data exist on the relationship of this polymorphism to risk of colorectal neoplasia in humans. We show that individuals homozygous for the minor ODC A-allele who reported using aspirin are approximately 0.10 times as likely to have an adenoma recurrence as non-aspirin users homozygous for the major G-allele. Mad1 selectively suppressed the activity of the ODC promoter containing the A-allele, but not the G-allele, in a human colon cancer-derived cell line (HT29). Aspirin (>or=10 microM) did not affect ODC allele-specific promoter activity but did activate polyamine catabolism and lower polyamine content in HT29 cells. We propose that the ODC polymorphism and aspirin act independently to reduce the risk of adenoma recurrence by suppressing synthesis and activating catabolism, respectively, of colonic mucosal polyamines. These findings confirm the hypothesis that the ODC polymorphism is a genetic marker for colon cancer risk, and support the use of ODC inhibitors and aspirin, or other nonsteroidal antiinflammatory drugs (NSAIDs), in combination as a strategy for colon cancer prevention.