Search

Despite some notable successes, there are still relatively few agents approved for cancer prevention. Here we review progress thus far in the development of medicines for cancer prevention, and we outline some key concepts that could further enable or accelerate drug development for cancer prevention in the future. These are summarized under six key themes: (i) unmet clinical need, (ii) patient identification, (iii) risk stratification, (iv) pharmacological intervention, (v) clinical trials, and (vi) health care policy. These concepts, if successfully realized, may help to increase the number of medicines available for cancer prevention.Significance:The huge potential public health benefits of preventing cancer, combined with recent advances in the availability of novel early detection technologies and new treatment modalities, has caused us to revisit the opportunities and challenges associated with developing medicines to prevent cancer. Here we review progress in the field of developing medicines to prevent cancer to date, and we present a series of ideas that might help in the development of more medicines to prevent cancer in the future.

Tables that provide additional information to support the main article

Purpose Using patient-reported outcomes in routine cancer care may improve health outcomes. However, a lack of information about which scores are problematic in specific populations can impede use. To facilitate interpretation of the European Organisation for Research and Treatment of Cancer Core Questionnaire (EORTC QLQ-C30), we identified cut-off scores that indicate need for support by comparing each scale to relevant items from the Supportive Care Needs Survey (SCNS-LF59) in a young adult (YA) population. Methods We conducted a cross-sectional survey amongst YAs with cancer ages 25–39 at diagnosis. Participants completed the EORTC QLQ-C30 and SCNS-LF59. Patient, clinician and research experts matched supportive care needs from the SCNS-LF59 to quality of life domains of the EORTC QLQ-C30. We evaluated the EORTC QLQ-C30 domain score’s ability to detect patients with need using receiver operator characteristic (ROC) analysis, calculating the area under the ROC curve and sensitivity and specificity for selected cut-offs. Cut-offs were chosen by maximising Youden’s J statistic and ensuring sensitivity passed 0.70. Sensitivity analyses were conducted to examine the variability of the cut-off scores by treatment status. Results Three hundred and forty-seven YAs took part in the survey. Six experts matched SCNS-LF59 items to ten EORTC QLQ-C30 domains. The AUC ranged from 0.78 to 0.87. Cut-offs selected ranged from 8 (Nausea and Vomiting and Pain) to 97 (Physical Functioning). All had adequate sensitivity (above 0.70) except the Financial Difficulties scale (0.64). Specificity ranged from 0.61 to 0.88. Four of the cut-off scores differed by treatment status. Conclusion Cut-offs with adequate sensitivity were calculated for nine EORTC QLQ-C30 scales for use with YAs with cancer. Cut-offs are key to interpretability and use of the EORTC QLQ-C30 in routine care to identify patients with supportive care need.

Background: Ataxia telangiectasia and Rad3-related (ATR) protein kinase plays a critical role in the DNA damage response. M1774, a potent, selective, orally administered ATR inhibitor with antitumor activity in preclinical models, was evaluated as monotherapy in Part A1 of the first-in-human open-label, single-arm study (NCT04170153). M1774 was well-tolerated and pharmacodynamic analyses showed that maximum target engagement was reached from the dose of 130 mg QD. The totality of evidence, including quantitative model-based analyses, suggested the recommended dose for expansion (RDE) as 180 mg QD 2 weeks on/1 week off.1 One patient with platinum and PARP inhibitor-resistant BRCAwt ovarian cancer and ATRX mutation on local tumor testing achieved an unconfirmed RECIST v1.1 partial response. Retrospective analyses were conducted to explore the molecular portrait and evolution of the underlying disease of patients treated with M1774. Methods: Archival tumor biopsies, baseline and serial on-treatment circulating tumor DNA (ctDNA) samples collected from patients enrolled in the study were analyzed by next generation sequencing. Somatic putative CHIP mutations and cases with mutation variant allele frequency (VAF) < 0.3% in circulating free DNA at baseline were excluded. Molecular response (MR) was defined as at least 50% reduction of VAF. Results: Molecular data were generated from archival biopsies collected for 33/55 patients and ctDNA samples from 55/55 patients enrolled in the study. High impact mutations were detected in ARID1A (N=10), ATM (N=5), ATRX (N=3), BRCA1/2 (N=13), and other homologous recombination-related genes (N=5). MRs were observed in 11/34 (32%) patients treated with more than 130 mg QD, none were observed in the 10 patients treated with lower doses. The MRs were enriched in patients with ovarian (3/8, 38%), prostate (4/8, 50%), and breast cancer (1/3, 33%), while less frequent (3/15, 25%) in other indications. TP53 mutations were significantly associated with MR, independently of tumor type. Complete MRs were achieved for any mutations in ARID1A (2/7), ATRX (2/5), DAXX (1/3), BRCA1/2 (1/10). A complete MR was seen in a patient with ovarian cancer with prolonged stable disease by RECIST (200 days), and ARID1A mutation in ctDNA. Conclusions: M1774 induced MRs in patients treated with doses in the predicted efficacious concentration range. TP53 alterations were significantly associated with MR. Complete MRs were detected for mutations in the genes ARID1A, ATRX, DAXX that are being tested for participant selection in the ongoing biomarker expansion cohorts of the DDRiver 301 study. 1TA Yap, et al. Ann Oncol. 2022; 33(suppl_7): S197-S224. Citation Format: Anthony W. Tolcher, Timothy A. Yap, Ruth Plummer, Thomas Grombacher, Danyi Wang, Corinna Schaffroth, Christine Hicking, Zoltan Szucs, Giuseppe Locatelli, Johann S. de Bono. Translational analyses of ATR inhibitor M1774 in a Phase I study in patients with solid tumors (DDRiver Solid Tumors 301) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr CT271.

Background: Ataxia telangiectasia and Rad3-related (ATR) protein kinase plays a critical role in the DNA damage response. M1774, a potent, selective, orally administered ATR inhibitor with antitumor activity in preclinical models, was evaluated in Part A1 of an open-label, single-arm study (NCT04170153) for safety, tolerability, maximum tolerated dose, pharmacokinetics (PK) and pharmacodynamics (PD). M1774 monotherapy in patients with advanced solid tumors was well-tolerated and the totality of evidence, including quantitative model-based analyses, suggested the recommended dose for expansion (RDE) as 180 mg QD 2 weeks on/1 week off.1 Here, we report findings of the M1774 PD and immunophenotyping analyses. Methods: M1774 PD was explored by assessing phosphorylation by ATR of CHK1 (p-CHK1) in tumor and of H2AX (γ-H2AX) in serial blood samples, stimulated ex vivo with the radiomimetic 4-Nitroquinoline N-oxide or Dimethyl sulfoxide as control. A flow cytometry quantitative assay was used to measure γ-H2AX in the CD45+ lymphocytes fraction. The effect of M1774 on the immunophenotype was explored by flow cytometry. Blood samples were collected at baseline, 3 and 24 hours after first M1774 administration on day 1 of cycle 1 for the γ-H2AX analysis, and on Days 1 and 15 of Cycles 1 and 2 before treatment for immunophenotyping. Results: Preclinical tumor tissue-blood bridging PD analyses in a mouse model demonstrated that the inhibition of γ-H2AX in lymphocytes highly correlated with inhibition of p-CHK1 in tumor. Clinical data of γ-H2AX levels and immunophenotyping were generated for the blood samples collected from the 55 participants of Part A1 of the study. Exploratory PK-PD analysis using γ-H2AX levels 3 h post-dose on day 1 across the doses predicted target inhibition >80% for doses ≥130 mg, suggesting target engagement. The levels of ɣ-H2AX at 24 h after first dose intake were variable and mean levels rebounded to baseline value. M1774 treatment did not cause any significant and consistent change in the levels of all explored immune cell subsets at the tested dose levels, including myeloid-derived suppressor cells, T and B lymphocytes, monocytes, and natural killer cells. Conclusions: PD analyses showed that M1774 efficiently inhibited ATR at the RDE without impacting the immunophenotype. 1TA Yap, et al. Ann Oncol. 2022; 33(suppl_7): S197-S224. Citation Format: Ruth Plummer, Anthony W. Tolcher, Timothy A. Yap, Giuseppe Sessa, Jatinder K. Mukker, Annick Seithel-Keuth, Christine Hicking, Zoltan Szucs, Ioannis Gounaris, Giuseppe Locatelli, Johann S. de Bono. Pharmacodynamic and immunophenotyping analyses of ATR inhibitor M1774 in a Phase I study in patients with solid tumors (DDRiver Solid Tumors 301) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr CT272.

Objective: Adolescents and young adults with cancer face unique psychosocial and practical issues. However, patients across this group encounter different life experiences, cancer diagnoses and treatment settings given the tailored services for patients ages 15 to 24. Here, we qualitatively explore the psychosocial experiences and practical challenges of young adults (YAs) with cancer diagnosed between ages 25 and 39 in the United Kingdom. Methods: We invited YAs diagnosed with cancer in the 5 years prior to enrolment at participating sites to take part in semi-structured interviews or focus groups. Transcripts were analysed using inductive thematic analysis. Two YA patients reviewed the results to ensure robustness. Results: Sixty-five YAs with varied diagnoses participated. Participants struggled to balance work, childcare and financial solvency with treatment. The halt in family and work life as well as changes in image and ability threatened participants’ identity and perceived ‘normality’ as a YA, however, these also stimulated positive changes. YAs experienced social isolation from friends and family, including children. Many struggled to cope with uncertainty around treatment outcomes and disease recurrence. Conclusion: The disruption of family and work life can lead to age-specific issues in YAs diagnosed with cancer. Age-tailored psychological and practical services must be considered.

Background Ductal carcinoma in situ (DCIS) is a non-invasive form of early breast cancer, with a poorly understood natural history of invasive transformation. Necrosis is a well-recognized adverse prognostic feature of DCIS, and non-invasive detection of its presence and spatial extent could provide information not obtainable by biopsy. We describe here imaging of the distribution and extent of comedo-type necrosis in a model of human DCIS using C2Am, an imaging agent that binds to the phosphatidylserine exposed by necrotic cells. Methods We used an established xenograft model of human DCIS that mimics the histopathological features of the disease. Planar near-infrared and optoacoustic imaging, using fluorescently labeled C2Am, were used to image non-invasively the presence and extent of lesion necrosis. Results C2Am showed specific and sensitive binding to necrotic areas in DCIS tissue, detectable both in vivo and ex vivo. The imaging signal generated in vivo using near-infrared (NIR) fluorescence imaging was up to 6-fold higher in DCIS lesions than in surrounding fat pad or skin tissue. There was a correlation between the C2Am NIR fluorescence (Pearson R = 0.783, P = 0.0125) and optoacoustic signals (R > 0.875, P Conclusions C2Am is a targeted multi-modal imaging agent that could complement current anatomical imaging methods for detecting DCIS. Imaging the presence and spatial extent of necrosis may give better prognostic information than that obtained by biopsy alone.

Few studies describe supportive care needs among young adults (YAs) with cancer ages 25 to 39 using validated questionnaires. Previous findings identified the need for psychological and information support and suggest that gender, age, psychological distress, and coping may be associated with greater need for this support. To substantiate these findings, this study aimed to (1) describe the supportive care needs of YAs in each domain of the Supportive Care Needs Survey and (2) explore the relationship between unmet supportive care needs and clinical and demographic factors, health-related quality of life, psychological distress, illness cognitions, and service needs using latent class analysis. Clinical teams from six hospitals in England invited eligible patients to a cross-sectional survey by post. A total of 317 participants completed the survey online or on paper. YAs expressed the most need in the psychological and sexuality domains. Using latent class analysis, we identified three classes of YAs based on level of supportive care need: no need (53.3%), low need (28.3%), and moderate need (18.4%). In each class, median domain scores in each domain were similar. Low and moderate need classes were associated with worse health-related quality of life and greater helplessness. Unmet service needs were associated with the moderate-need class only. Patients with unmet supportive care needs should be offered holistic care across supportive care domains.

Additional file 1: Figure S1 Fluorescence imaging (a) of C2Am and iC2Am standard solutions. Excitation (dashed) and emission (filled) profiles (b) of iC2Am-650 (Ex/Em: 652|672 nm, red, left) and C2Am-750 (Ex/Em: 753|783 nm, brown, right). Serial dilutions (decreasing concentration, left to right) of the imaging probes (c, e) were imaged on an IVIS200™ system and the mean fluorescence intensity (in radiant efficiency) correlated with probe concentration, in the far red (d) and near infra-red NIR (f), for C2Am (open circles) and iC2Am (closed squares). iC2Am fluorescence (d) in the far-red (black squares) was minimal (ca. 10% of that of C2Am, open circles). C2Am fluorescence (f) in the NIR was undetectable. Fluorescence intensities (g) of C2Am-650 (in the far-red, open circles in g, data in 2nd row of c) and iC2Am-750 (in the NIR, closed squares in g, data in the top row of e) were identical at all concentrations. A 1:1 molar mixture (h) of C2Am|iC2Am (c, e, lower row) was also imaged in the far-red (open circles) and NIR (closed squares) showing equivalent readouts at all concentrations, in the range 40-2,500 nM. Figure S2. Single wavelength OA images of (a) phantoms (b) and in vivo tumor models are illustrated with the regions of interest (ROIs) used for the data analysis outlined. (c) OA spectra of iC2Am and C2Am molecules were obtained from multispectral imaging of the probes using tissue mimicking phantoms.

Contains fulltext : 235257.pdf (Publisher’s version ) (Open Access) AIMS: Adolescents and young adults aged 15-39 years with cancer face unique medical, practical and psychosocial issues. In the UK, principal treatment centres and programmes have been designed to care for teenage and young adult patients aged 13-24 years in an age-appropriate manner. However, for young adults (YAs) aged 25-39 years with cancer, little access to age-specific support is available. The aim of this study was to examine this possible gap by qualitatively exploring YA care experiences, involving patients as research partners in the analysis to ensure robust results. MATERIALS AND METHODS: We conducted a phenomenological qualitative study with YAs diagnosed with any cancer type between ages 25 and 39 years old in the last 5 years. Participants took part in interviews or focus groups and data were analysed using inductive thematic analysis. Results were shaped in an iterative process with the initial coders and four YA patients who did not participate in the study to improve the rigor of the results. RESULTS: Sixty-five YAs with a range of tumour types participated. We identified seven themes and 13 subthemes. YAs found navigating the healthcare system difficult and commonly experienced prolonged diagnostic pathways. Participants felt under-informed about clinical details and the long-term implications of side-effects on daily life. YAs found online resources overwhelming but also a source of information and treatment support. Some patients regretted not discussing fertility before cancer treatment or felt uninformed or rushed when making fertility preservation decisions. A lack of age-tailored content or age-specific groups deterred YAs from accessing psychological support and rehabilitation services. CONCLUSIONS: YAs with cancer may miss some benefits provided to teenagers and young adults in age-tailored cancer services. Improving services for YAs in adult settings should focus on provision of age-specific information and access to existing relevant support.

GluCAB is a newly synthesised macrocyclic radioligand designed to bind in vivo to albumin (HSA) for the purpose of development as a dual-targeting oncological theranostic agent. Subsequent to its synthesis and 64Cu-radiolabelling, this radioligand has show a prolonged circulation time in healthy mice but with appropriate systemic clearance within 24 h. This radioligand meets the criteria to be further investigated for tumour targeting and uptake.

Contains fulltext : 170336.pdf (Publisher’s version ) (Open Access) Desmoid tumour/aggressive fibromatosis (DT/AF) is a rare soft-tissue neoplasm that is locally aggressive but does not metastasize. There is no standard systemic treatment for symptomatic patients, although a number of agents are used. Tyrosine kinase inhibitors have recently been reported to show useful activity. We reviewed our bi-institutional (Royal Marsden Hospital, Cambridge University Hospitals) experience with the tyrosine kinase inhibitor pazopanib in the treatment of progressing DT/AF. Eight patients with DT/AF were treated with pazopanib at Royal Marsden Hospital and Cambridge University Hospitals between June 2012 and June 2016. The median age of the patients was 37.5 (range: 27-60) years. The median duration of pazopanib treatment was 12 (range: 5-22) months and for three patients the treatment is ongoing. Three patients discontinued treatment early (patient preference, intolerable toxicity and logistical reasons, respectively). None of the patients showed radiological progression while on treatment, best responses according to Response Evaluation Criteria In Solid Tumors 1.1 were partial response in 3/8 and stable disease in 5/8 cases. Six patients derived clinical benefit from treatment in terms of improved function and/or pain reduction. Median progression-free survival was 13.5 (5-36) months. Only one patient experienced intolerable toxicity (grade 3 hypertension) leading to early treatment discontinuation. In our series of patients with DT/AF, pazopanib demonstrated important activity both in terms of symptom control (75%) and absence of radiological progression (100%). Results of ongoing confirmatory trials are eagerly awaited.

Sarcoma Unit, Royal Marsden Hospital, London, SW3 6JJ, UK *Author for correspondence: Tel.: +44 020 7808 2137; Fax: +44 207 808 2113; robin.jones@rmh.nhs.uk

Background: Data on temozolomide (TEM) and irinotecan (IRI) activity in recurrent Ewing sarcoma (EWS), especially in adult patients, are limited. Methods: Patients receiving TEM 100 mg/m2/day oral, and IRI 40 mg/m2/day intravenous, days 1–5, every 21 days, were included in this multi-institutional retrospective study. Disease control rate (DCR) [overall response rate (ORR) [complete response (CR) + partial response (PR)] + stable disease (SD)], 6-months progression-free survival (6-mos PFS) and 1-year overall survival (OS) were assessed. Results: The median age of the 51 patients was 21 years (range 3–65 years): 34 patients (66%) were adults (≥18 years of age), 24 (48%) had ECOG 1 and 35 (69%) were presented with multiple site recurrence. TEMIRI was used at first relapse/progression in 13 (25%) patients, while the remainder received TEMIRI for second or greater relapse/progression. Fourteen (27%) patients had received prior myeloablative therapy with busulfan and melphalan. We observed five (10%) CR, 12 (24%) PR and 19 (37%) SD, with a DCR of 71%. 6-mos PFS was 49% (95% CI 35–63) and it was significantly influenced by ECOG (6-mos PFS 64% [95% CI 45–83] for ECOG 0, 34% [95% CI 14–54] for ECOG ≥1; p =.006) and LDH (6-mos PFS 62% [95% CI 44–79] for normal LDH, 22% [95% CI 3–42] for high LDH; p =.02), with no difference according to line of treatment, age and metastatic pattern. One-year OS was 55% (95% CI 39–70), with RECIST response (p =.001) and ECOG (p =.0002) independently associated with outcome. Grade 3 and 4 toxicity included neutropenia in 12% of patients, thrombocytopenia in 4%, diarrhea in 4%. Conclusions: This series confirms the activity of TEMIRI in both adults and pediatric patients. This schedule offers a 71% DCR, independently of the line of chemotherapy. Predictive factors of response are ECOG and LDH.

Background. National guidelines prompted the implementation of a designated two-week wait referral pathway to facilitate the early diagnosis of sarcomas, to improve treatment outcomes.Methods. Patients referred to the Cambridge Sarcoma Diagnostic Clinic between January 2013 and December 2014 were identified through the electronic appointments system. Information was retrospectively retrieved about patient characteristics and details of the diagnostic pathway.Results. 17.3% of patients referred (69/397) were diagnosed with a malignancy. Of these, 59.3% (41/69) had primary sarcomas, 17.4% (12/69) had metastatic cancer, and 23.2% (16/69) had a different primary malignancy. 15% of the 41 sarcomas were 10 cm. Sarcomas diagnosed through this clinic represented 13% (41/315) of sarcomas managed at the centre during the same 2 years.Conclusion. While we achieved the target of 10% (41/397) sarcoma diagnosis rate in the rapid access clinic, only 15% of these were

Gastrointestinal stromal tumours (GISTs) represent a very exciting tumour entity for the medical oncologist. There has been extensive clinical and preclinical research dissecting the natural behaviour, molecular landscape and therapeutic responsiveness of this rare mesenchymal tumour. Various molecular subtypes of GIST have a differing prognostic and predictive relevance in the state of the art management of the disease. Emerging mature clinical trial data gathered over the last one and half decade provided substantial molecular profiling information in understanding the success and eventual failure of treatment. In our review of the most relevant literature we aim to guide the clinician in tailoring neoadjuvant, adjuvant and palliative treatment of GIST alongside the different, now well established molecular subgroups of GISTs.

Contains fulltext : 200567.pdf (Publisher’s version ) (Open Access) Background: One of the commonly used systemic agents for the treatment of aggressive fibromatosis is the anti-oestrogen drug tamoxifen. However, data on efficacy and optimum methods of response assessment are limited, consisting mainly of small case series and reports. Methods: A retrospective database was used to identify consecutive patients diagnosed with aggressive fibromatosis (AF) and treated with tamoxifen plus/minus non-steroidal anti-inflammatory drugs at our tertiary referral centre between 2007 and 2014. MRI and symptom changes were recorded. Results: Thirty-two patients (13 male 19 female, median age 41 years) were included. Median duration of treatment with tamoxifen was 316 days. Of 9 patients with progressive disease by RECIST 1.1 (28%): 4 patients experienced worsening symptoms; 3 patients had improved symptoms and 2 had no change in symptoms. Of 22 patients with stable disease (69%): 11 had no change in symptoms; 6 had improved symptoms and 5 patients had worsening symptoms. One patient achieved a partial response with improved symptoms. Conclusions: No relationship was identified between symptomatic benefit and response by RECIST 1.1 on MRI. Prospective studies in AF should incorporate endpoints focusing on patient symptoms.

Dinuclearbisphosphinogold(I) dithiocarbamato, BPDTC, was previously found to have antitumour activity in vitro. 198Au radiolabelled BPDTC (radiochemical yield of 70 ± 6 % and radiochemical purity of[95 %) was used to determine its in vivo biodistribution in Sprague-Dawley rats. Gamma scintigraphs were performed over a period of 48 h and final radioactivity measurements of harvested organs of the test animals after termination was performed at 2, 4 and 48 h. The study successfully showed the biodistribution of the gold complex, with the highest uptake of the compound being observed in the lungs, liver and spleen Nuclear Technologies in Medicine and the Biosciences Initiative (NTeMBI), a national technology platform developed and managed by the South African Nuclear Energy Corporation (Necsa) and funded by the Department of Science and Technology. Biomed (Mintek)

Phenylacetate has been reported to have a potent anti-proliferative and anti-differentiating effect in haematological malignancies and in solid tumours at non-toxic concentrations. This study is a preliminary investigation of 131I-radiolabelled 4-iodophenylacetic acid as a potential radiopharmaceutical equivalent. Radiolabelling by isotope exchange gave a radiochemical yield of 53 ± 6 %, and a radiochemical purity of 97.8 ± 1.2 %, as qualified by HPLC. The labelled product was used in Sprague Dawley rats and athymic nude (balb/c) mice xenografted with WHCO1 cells (an oesophageal cancer cell line). Dynamic and static scans were carried out on rats with a SPECT camera to determine the biodistribution of 4-[131I]-iodophenylacetic acid. No target organ was found after 5 h with fast excretion from all organs via the kidney into the urine. Ex vivo studies (termination 5 h after injection) were performed in 12 xenograft mice carrying tumours of 5-8 mm on their right flank. Tumour uptake of 4 + 0.4 % ID/g was recorded with a tumour to background ratio of 2. As the blood pool still contains high levels of activity after 5 h in mice, increased tumour uptake may occur at later time points, which might warrant further investigation http://www.eurekaselect.com/672/journal/current-radiopharmaceuticals

The pathogenesis of breast cancer is polygenic. Exploring the involvement of different onco- and tumor suppressor genes, and combinations of these genes, in early breast cancer formation is important for understanding the natural history of the disease. Preclinical studies of the fundamental biological and metabolic changes that occur during breast oncogenesis in currently available transgenic mouse models are limited by the requirement for tissue-specific promoters and the random nature of tumor formation. The mouse mammary gland is a unique organ in that most of its development occurs after birth. Moreover, isolated mammary epithelial cells (MECs) have the capacity to regenerate a functional gland upon orthotopic transplantation into the cleared fat pad of a syngeneic recipient. We describe here a new transplantation system using pure MECs derived from genetically engineered mice harboring floxed oncogenes. First we selected in vitro for a stromal and hematopoietic cell-free MEC preparation. In the MEC donor transgenic strains the activation of oncogenes (K-Ras, c-Myc) or the deletion of tumor suppressors (p53) is dependent on Cre recombinase expression (Cre-lox system). Using an adenoviral Cre-recombinase vector we activated these oncogenic changes in isolated MECs. Colony formation assays demonstrated the viability of these mixed transduced/non-transduced MEC populations. Following transplantation into the cleared fat pad of syngeneic mice the transduced MECs preserved their fat pad repopulating and duct forming potential and the induced oncogenic changes resulted in mammary tumor formation. This proposed system offers tissue specific promoter-free and lactation independent spatial control of oncogenic events in the epithelial cell compartment of breast ducts. Citation Format: Zoltan Szucs, Michael D. Prater, John Stingl, Kevin M. Brindle. A novel orthotopic mammary epithelial cell (MEC) transplantation model of breast cancer formation. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 78. doi:10.1158/1538-7445.AM2014-78