Detection of metabolic adaptation in a triple-negative breast cancer animal model with [18F]choline-PET imaging as a surrogate for drug resistance

PURPOSE

Test the feasibility of an image-based method to identify taxane resistance in mouse bearing triple-negative breast cancer (TNBC) tumor xenografts.

METHODS

Xenograft tumor-bearing mice from paclitaxel-sensitive and paclitaxel-resistant TNBC cells (MDA-MD-346) were generated by orthotopic injection into female NOD-SCID mice. When tumors reached 100-150 mm3, mice were scanned using [18F]choline PET/CT. Tumors were collected and sliced for autoradiography and immunofluorescence analysis. Quantitative data was analyzed accordingly.

RESULTS

From fifteen mice scanned, five had taxane-sensitive cell line tumors of which two underwent taxol-based treatment. From the remaining 10 mice with taxane-resistant cell line tumors, four underwent taxol-based treatment. Only 13 mice had the tumor sample analyzed histologically. When normalized to the blood pool, both cell lines showed differences in metabolic uptake before and after treatment.

CONCLUSIONS

Treated and untreated taxane-sensitive and taxane-resistant cell lines have different metabolic properties that could be leveraged before the start of chemotherapy.

Reply to Trudeau, M.; Fraser, B. The CADTH pCODR Expert Review Committee Process Explained. Comment on "Rayson et al. Access to Neoadjuvant Pertuzumab for HER2 Positive Breast Cancer in Canada: A Dilemma Increasingly Difficult to Explain. Curr. Oncol. 2022, 29, 9891-9895"

We appreciate the opportunity to respond to the comment [...].

Abstract 90: Exploring the role of common circulating tumor cell-associated genes in estrogen receptor-positive breast cancer recurrence

Despite having the best survival among the molecular subtypes, estrogen receptor-positive (ER+) breast cancer has a tendency for late recurrence. Circulating tumor cells (CTCs) are responsible for disease recurrence by seeding tumors at secondary sites. We have previously developed a CTC signature of 90 common regions of gene copy number gain and demonstrated that this signature is significantly more widespread among cells in metastases than primary tumors.1,2 The objective of our current work is to establish whether the expression data from a 133 gene panel largely derived from the CTC signature can be used to assess the risk of recurrence (ROR) in early ER+ breast cancer patients to help guide treatment decisions following surgery. Formalin-fixed, paraffin-embedded (FFPE) ER+ breast tumor biopsies and linked normal (control) tissues from 192 patients are being analyzed with a custom NanoString nCounter probe set of our 133 CTC genes. From data gathered to date, several genes were shown to be significantly overexpressed in tumors compared to reference normal tissues. This includes MMP11, MKI67, LILRB4, UBE2T, BIRC5, CDC6, MYBL2, and NUF2, which had a log2 fold-change of at least 3.5 (n = 34, p < 0.01). The correlation of our CTC genes to ROR is being evaluated by comparison to the results of the Oncotype DX Breast Recurrence Score Test, a well-established clinical test for ROR in ER+ breast cancer, for each patient. So far, it has been shown that the intratumor heterogeneity (ITH) of CTC genes as established by DEPTH2, an ITH algorithm which evaluates mRNA levels, is significantly positively corelated to Oncotype DX score (n = 23, r = 0.41, p = 0.0495). Moving forward, we will create our own ROR scoring system based on gene expression and copy number data from the CTC gene panel and validate it by comparison to Oncotype DX score and other available clinical data for each of the 192 patient samples. The goal of our work is to gain a deeper understanding of the molecular mechanisms that drive metastasis and recurrence in ER+ breast cancer by focusing on CTCs which play a pivotal role in driving these events.

1. Kanwar N, Hu P, Bedard P, Clemons M, McCready D, Done SJ. Identification of genomic signatures in circulating tumor cells from breast cancer. International Journal of Cancer. 2015;137(2):332-344. doi:10.1002/ijc.29399

2. Kanwar N, Balde Z, Nair R, et al. Heterogeneity of Circulating Tumor Cell-Associated Genomic Gains in Breast Cancer and Its Association with the Host Immune Response. Cancer Research. 2021;81(24):6196-6206. doi:10.1158/0008-5472.can-21-1079‌

Citation Format: Martin Rotbauer, Melanie Dawe, Philippe Bedard, David Cescon, Susan Done. Exploring the role of common circulating tumor cell-associated genes in estrogen receptor-positive breast cancer recurrence [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 90.

Access to Neoadjuvant Pertuzumab for HER2 Positive Breast Cancer in Canada: A Dilemma Increasingly Difficult to Explain

The addition of pertuzumab to neoadjuvant trastuzumab and chemotherapy for women with early-stage, high-risk, HER2+ breast cancer has been observed to lead to higher pathologic complete response rates (pCR), and improved event-free survival compared to trastuzumab and chemotherapy alone. Based on available data, neoadjuvant pertuzumab is recommended by ESMO, ASCO, and NICE as well as by a Canadian Consensus Guideline Group. We discuss the implications for Canadian patients with HER2+ early breast cancer due to a second and final negative funding decision by the Canadian Agency for Drugs and Technologies in Health (CADTH) related to neoadjuvant pertuzumab. This decision will have adverse impacts for up to 1 in 6 women receiving neoadjuvant therapy for high-risk HER2+ breast cancer, due to suboptimal pCR rates and higher risks of invasive breast cancer recurrent events, resulting in the need for more toxic adjuvant therapy.

Abstract OT-30-01: KEYLYNK-009: A phase 2/3, open-label, randomized study of pembrolizumab plus olaparib vs pembrolizumab plus chemotherapy after induction with first-line pembrolizumab plus chemotherapy in patients with locally recurrent inoperable or metastatic triple-negative breast cancer (TNBC)

Background: Combination therapy with immunotherapy + chemotherapy is a promising approach for first-line treatment of locally recurrent, inoperable TNBC or metastatic TNBC (mTNBC). However, an unmet need exists for effective and tolerable maintenance regimens in mTNBC to sustain clinical benefit after induction therapy and avoid potential toxicity or resistance to prolonged chemotherapy. The poly (ADP-ribose) polymerase (PARP) inhibitor olaparib has shown efficacy in the maintenance setting for platinum-sensitive ovarian cancer, and the high prevalence of BRCA mutations (or “BRCAness”) in TNBC may make these tumors particularly sensitive to DNA-damaging agents. Moreover, evidence suggests that combination therapy with olaparib and the PD-1 inhibitor pembrolizumab may provide clinical benefit greater than treatment with either single-agent. KEYLYNK-009 (NCT04191135) is a phase 2/3, open-label, randomized study of pembrolizumab + olaparib or pembrolizumab + chemotherapy after induction with first-line pembrolizumab + chemotherapy in patients with locally recurrent, inoperable TNBC or mTNBC.Methods: This 2-in-1 study design will enroll ~317 patients in phase 2; if a planned efficacy boundary is met, ~615 additional patients will be enrolled in phase 3. Patients eligible for induction therapy must have measurable, locally recurrent, inoperable TNBC that cannot be treated with curative intent or mTNBC previously untreated with chemotherapy in the metastatic setting. All patients will receive up to 6 cycles of induction therapy with pembrolizumab 200 mg Q3W + chemotherapy (carboplatin AUC 2 + gemcitabine 1000 mg/m2 on days 1 and 8 Q3W). Patients eligible for postinduction treatment must achieve complete or partial response or maintain stable disease during induction after 4-6 treatment cycles, with ECOG PS 0/1 and no persistent grade >1 toxicities related to induction therapy (excluding alopecia, hemoglobin ≥9.0 g/dL, grade 2 hyper-/hypothyroidism, or grade 2 hyperglycemia). These patients will be randomized 1:1 to receive pembrolizumab 200 mg Q3W + olaparib 300 mg twice daily or continue pembrolizumab + chemotherapy (same as induction regimen). Olaparib and chemotherapy may continue until progression or unacceptable toxicity; pembrolizumab may continue for ≤35 cycles (including induction), unacceptable toxicity, or progression. Phase 3 dual primary endpoints are PFS per RECIST version 1.1 by blinded independent central review and OS. Secondary endpoints are OS and PFS in patients with BRCA mutation, health-related quality of life, and safety. PFS and OS will be estimated using the Kaplan-Meier method, treatment differences will be assessed using a stratified log-rank test, and HRs and 95% CIs will be assessed using a stratified Cox proportional hazard model with Efron's method of tie handling. AEs are monitored until 30 days (90 days for serious AEs) after treatment discontinuation per NCI CTCAE version 5.0. Patient enrollment is ongoing with a total planned enrollment of 932 patients. Contact Hope S. Rugo at hope.rugo@ucsf.edu for additional information.

Citation Format: Hope Rugo, Antonio Llombart-Cussac, Fabrice Andre, Mark E. Robson, Shigehira Saji, Nadia Harbeck, Peter Schmid, David Cescon, Jin Seok Ahn, Rita Nanda, Li Fan, Jaime Alberto Mejia, Vassiliki Karantza, Aditya Bardia. KEYLYNK-009: A phase 2/3, open-label, randomized study of pembrolizumab plus olaparib vs pembrolizumab plus chemotherapy after induction with first-line pembrolizumab plus chemotherapy in patients with locally recurrent inoperable or metastatic triple-negative breast cancer (TNBC) [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr OT-30-01.

Abstract PD4-02: Canadian cancer trials group trial IND.231: A phase 1 trial evaluating CX-5461, a novel first-in-class G-quadruplex stabilizer in patients with advanced solid tumors enriched for DNA-repair deficiencies

Background: G-quadruplexes are secondary DNA structures that reversibly form in guanine-rich regions within DNA. Our group has demonstrated that CX-5461 selectively binds and stabilizes G-quadruplex structures, causing replication fork collapse and double-stranded DNA breaks. In BRCA1/2 deficient cell lines and xenograft models, synthetic lethality was observed. We are conducting a phase I study of CX-5461, a first-in-class G-quadruplex stabilizer, in patients with advanced solid tumors enriching for patients with DNA-repair deficiencies. Methods: We conducted a phase I study of 10 dose levels of CX-5461. The initial 7 dose levels (50, 100, 150, 200, 250, 325, 475 mg/m2) were administered intravenously on days 1 and 8 of a 4-week cycle, while the final 3 dose levels (325, 475 and 650 mg/m2) were administered intravenously on days 1, 8 and 15 of a 4-week cycle. Escalation was performed using a 3+3 design. Eligible patients must have advanced disease, a PS 0-2 and adequate organ function. Patients were treated until disease progression. The primary objective was the determination of RP2D. The DLT evaluation period was cycle 1 and AEs needed to be maximally managed to be considered a DLT. Secondary objectives include ORR (RECIST 1.1), PK, and toxicity (CTCAEv4.0). Results: As of March 28th, 2019, 40 patients were registered on protocol with 39 patients evaluable for toxicity and 35 patients evaluable for response. 18 of the participants were diagnosed with metastatic breast cancer. Of the evaluable patients, the median age is 53 with 24 patients having 3 or more prior regimens for their disease. There have been no DLTs observed to date. There were 5 treatment-related non-DLT grade 3 photosensitivity events (DL0, DL4, DL7, DL8, DL9) that were reversible and were secondary to lack of photo-protective measures. 3 SAEs were considered related to CX-5461 (photosensitivity of the skin (n=2); photosensitivity of the eyes (n=1). Treatment-related AEs ≥10% were photosensitivity of the skin (59%), photosensitivity of the eyes (21%), mucositis (15%), nausea (44%), hand-foot syndrome (23%), headache (10%) and rash (10%). The RP2D was determined to be 475 mg/m2 on days, 1, 8 and 15 of a 4-week cycle. PK appears dose-proportional for Cmax and AUC24,∞. Of the 40 patients treated on protocol, 34 have discontinued from the study either due to objective progressive disease (n=29), symptomatic progression of disease (n=4) or withdrawal of consent (n=1). In terms of best response, 4 patients, including 3 with breast cancer, have a confirmed PR (2 germline BRCA2, 1 germline BRCA2 VUS, germline PALB2) with an additional 6 patients, including 2 with breast cancer, (4 germline BRCA2, 2 somatic BRCA1/2) with SD as best response for >=4 cycles. Conclusion: CX-5461 is tolerable with preventable photosensitivity being the main toxicity. The RP2D is now identified at 475 mg/m2 on days 1, 8 and 15 of a 4-week cycle. Preliminary activity for CX-5461 has been observed in patients with HR-deficient tumors for both breast cancer and other tumor types. An expansion cohort, with mandatory tumor and skin biopsies, for patients with metastatic breast cancer with confirmed HR deficiency is currently open. Further updates will be provided.

Citation Format: John Hilton, Karen Gelmon, David Cescon, Anna Tinker, Derek Jonker, Rachel Goodwin, Scott Laurie, Aaron Hansen, Samuel Aparicio, John Soong, Linda Hagerman, Hongbo Lui, Philippe Bedard, Kathleen Pritchard, Dongsheng Tu, Lesley Seymour. Canadian cancer trials group trial IND.231: A phase 1 trial evaluating CX-5461, a novel first-in-class G-quadruplex stabilizer in patients with advanced solid tumors enriched for DNA-repair deficiencies [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr PD4-02.

If we build it they will come: targeting the immune response to breast cancer

Historically, breast cancer tumors have been considered immunologically quiescent, with the majority of tumors demonstrating low lymphocyte infiltration, low mutational burden, and modest objective response rates to anti-PD-1/PD-L1 monotherapy. Tumor and immunologic profiling has shed light on potential mechanisms of immune evasion in breast cancer, as well as unique aspects of the tumor microenvironment (TME). These include elements associated with antigen processing and presentation as well as immunosuppressive elements, which may be targeted therapeutically. Examples of such therapeutic strategies include efforts to (1) expand effector T-cells, natural killer (NK) cells and immunostimulatory dendritic cells (DCs), (2) improve antigen presentation, and (3) decrease inhibitory cytokines, tumor-associated M2 macrophages, regulatory T- and B-cells and myeloid derived suppressor cells (MDSCs). The goal of these approaches is to alter the TME, thereby making breast tumors more responsive to immunotherapy. In this review, we summarize key developments in our understanding of antitumor immunity in breast cancer, as well as emerging therapeutic modalities that may leverage that understanding to overcome immunologic resistance.

A phase II randomized clinical trial of the effect of metformin versus placebo on progression-free survival in women with metastatic breast cancer receiving standard chemotherapy

OBJECTIVES

Pre-clinical data suggest metformin might enhance the effect of chemotherapy in breast cancer (BC). We conducted a Phase II randomized trial of chemotherapy plus metformin versus placebo in metastatic breast cancer (MBC).

MATERIAL AND METHODS

In this double blind phase II trial we randomly assigned non-diabetic MBC patients on 1st to 4th line chemotherapy to receive metformin 850 mg po bid or placebo bid. Primary outcome was progression-free survival (PFS); secondary outcomes included overall survival (OS), response rate (RR), toxicity and quality of life (QOL). With 40 subjects and a type-one error of 0.2 (one-sided), a PFS hazard ratio (HR) of 0.58 could be detected with 80% power.

RESULTS

40 patients were randomized (22 metformin, 18 placebo) with a mean age of 55 vs 57 years and ER/PR positive BC in 86.4% vs 83.3% off metformin vs placebo, respectively. Mean BMI was 27kg/m2 in both arms. The majority of patients were on 1st line chemotherapy. Grade 3-4 toxicity occurred in 31.8% (metformin) vs 58.8% (placebo). Best response: Partial response 18.2% metformin vs 25% placebo, stable disease 36.4% metformin vs 18.8% placebo, progressive disease 45.4% metformin vs 56.2% placebo. Mean PFS was 5.4 vs 6.3 months (metformin vs placebo), HR 1.2 (95% CI 0.63-2.31). Mean OS was 20.2 (metformin) vs 24.2 months (placebo), HR 1.68 (95% CI 0.79-3.55).

CONCLUSION

In this population metformin showed no significant effect on RR, PFS or OS. These results do not support the use of metformin with chemotherapy in non-diabetic MBC patients.

MicroSPECT/CT Imaging of Cell-Line and Patient-Derived EGFR-Positive Tumor Xenografts in Mice with Panitumumab Fab Modified with Hexahistidine Peptides To Enable Labeling with 99mTc(I) Tricarbonyl Complex

We aimed to investigate the feasibility of conjugating synthetic hexahistidine peptides (His₆) peptides to panitumumab Fab (PmFab) to enable labeling with [^99mTc(H₂O)₃(CO)₃]⁺ complex and study these radioimmunoconjugates for imaging EGFR-overexpressing tumor xenografts in mice by microSPECT/CT. Fab were reacted with a 10-fold excess of sulfo-SMCC to introduce maleimide functional groups for reaction with the terminal thiol on peptides [CGYGGHHHHHH] that harbored the His₆ motif. Modification of Fab with His₆ peptides was assessed by SDS-PAGE/Western blot, and the number of His₆ peptides introduced was quantified by a radiometric assay incorporating ¹²³I-labeled peptides into the conjugation reaction. Radiolabeling was achieved by incubation of PmFab-His₆ in PBS, pH 7.0, with [^99mTc(H₂O)₃(CO)₃]⁺ in a 1.4 MBq/μg ratio. The complex was prepared by adding [^99mTcO₄]^- to an Isolink kit (Paul Scherrer Institute). Immunoreactivity was assessed in a direct (saturation) binding assay using MDA-MB-468 human triple-negative breast cancer (TNBC) cells. Tumor and normal tissue uptake and imaging properties of ^99mTc-PmFab-His₆ (70 μg; 35-40 MBq) injected i.v. (tail vein) were compared to irrelevant ^99mTc-Fab 3913 in NOD/SCID mice engrafted subcutaneously (s.c.) with EGFR-overexpressing MDA-MB-468 or PANC-1 human pancreatic ductal carcinoma (PDCa) cell-line derived xenografts (CLX) at 4 and 24 h post injection (p.i.). In addition, tumor imaging studies were performed with ^99mTc-PmFab-His₆ in mice with patient-derived tumor xenografts (PDX) of TNBC, PDCa, and head and neck squamous cell carcinoma (HNSCC). Biodistribution studies in nontumor bearing Balb/c mice were performed to project the radiation absorbed doses for imaging studies in humans with ^99mTc-PmFab-His₆. PmFab was derivatized with 0.80 ± 0.03 His₆ peptides. Western blot and SDS-PAGE confirmed the presence of His₆ peptides. ^99mTc-PmFab-His₆ was labeled to high radiochemical purity (≥95%), and the K_d for binding to EGFR on MDA-MB-468 cells was 5.5 ± 0.4 × 10^-8 mol/L. Tumor uptake of ^99mTc-PmFab-His₆ at 24 h p.i. was significantly (P < 0.05) higher than irrelevant ^99mTc-Fab 3913 in mice with MDA-MB-468 tumors (14.9 ± 3.1%ID/g vs 3.0 ± 0.9%ID/g) and in mice with PANC-1 tumors (5.6 ± 0.6 vs 0.5 ± 0.1%ID/g). In mice implanted orthotopically in the pancreas with the same PDCa PDX, tumor uptake at 24 h p.i. was 4.2 ± 0.2%ID/g. Locoregional metastases of these PDCa tumors in the peritoneum exhibited slightly and significantly lower uptake than the primary tumors (3.1 ± 0.3 vs 4.2 ± 0.3%ID/g; P = 0.02). In mice implanted with different TNBC or HNSCC PDX, tumor uptake at 24 h p.i. was variable and ranged from 3.7 to 11.4%ID/g and 3.8-14.5%ID/g, respectively. MicroSPECT/CT visualized all CLX and PDX tumor xenografts at 4 and 24 h p.i. Dosimetry estimates revealed that in humans, the whole body dose from administration of 740-1110 MBq of ^99mTc-PmFab-His₆ would be 2-3 mSv, which is less than for a ^99mTc-medronate bone scan (4 mSv).

Abstract 3378: Systematic pharmacogenomic analysis of large patient derived xenografts data

One of the key challenges in cancer precision medicine is finding robust biomarkers of drug response. Patient-derived tumor xenografts (PDXs) have emerged as reliable preclinical models since they better recapitulate tumor response to chemo- and targeted therapies. However, the lack of standard tools poses a challenge in the analysis of PDXs with molecular and pharmacological profiles. Efficient storage, access and analysis is key to the realization of the full potential of PDX pharmacogenomic data. To address this, we have developed Xeva (XEnograft Visualization & Analysis), an open-source software package for processing, visualization and integrative analysis of a compendium of in vivo pharmacogenomic datasets. The Xeva package follows the PDX minimum information (PDX-MI) standards and can handle both replicate-based and 1x1x1 experimental designs. We used Xeva to characterize the variability of gene expression and pathway activity across passages. We found that only a few genes and pathways have passage specific alterations (median intraclass correlation of 0.53 for genes and positive enrichment score for 92.5% pathways). For example, activity of the mRNA 3'-end processing and elongation arrest and recovery pathways were strongly affected by model passaging (gene set enrichment analysis false discovery rate [FDR] &lt;5%). We then leveraged our platform to link the drug response and the pathways whose activity is consistent across passages by mining the Novartis PDX Encyclopedia (PDXE) data containing 1,075 PDXs spanning 5 tissue types and 62 anticancer drugs. We identified 87 pathways significantly associated with response to 51 drugs (FDR &lt; 5%), including associations such as erlotinib response and signaling by EGFR in cancer pathways and MAP kinase activation in TLR cascade and binimetinib response. Among the significant pathway-drug associations, we found novel biomarkers based on gene expressions, Copy Number Aberrations (CNAs) and mutations predictive of drug response (concordance index &gt; 0.60; FDR &lt; 0.05). Xeva provides a flexible platform for integrative analysis of preclinical in vivo pharmacogenomics data to identify biomarkers predictive of drug response, a major step toward precision oncology.

Citation Format: Arvind Singh Mer, Wail Ba-alawi, Petr Smirnov, Yi Xiao Wang, Ben Brew, Ming-Sound Tsao, David Cescon, Anna Goldenberg, Benjamin Haibe-Kains. Systematic pharmacogenomic analysis of large patient derived xenografts data [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3378.

An interim report on the investigator-initiated phase 2 study of pembrolizumab immunological response evaluation (INSPIRE)

Background

Immune checkpoint inhibitors (ICIs) demonstrate unprecedented efficacy in multiple malignancies; however, the mechanisms of sensitivity and resistance are poorly understood and predictive biomarkers are scarce. INSPIRE is a phase 2 basket study to evaluate the genomic and immune landscapes of peripheral blood and tumors following pembrolizumab treatment.

Methods

Patients with incurable, locally advanced or metastatic solid tumors that have progressed on standard therapy, or for whom no standard therapy exists or standard therapy was not deemed appropriate, received 200 mg pembrolizumab intravenously every three weeks. Blood and tissue samples were collected at baseline, during treatment, and at progression. One core biopsy was used for immunohistochemistry and the remaining cores were pooled and divided for genomic and immune analyses. Univariable analysis of clinical, genomic, and immunophenotyping parameters was conducted to evaluate associations with treatment response in this exploratory analysis.

Results

Eighty patients were enrolled from March 21, 2016 to June 1, 2017, and 129 tumor and 382 blood samples were collected. Immune biomarkers were significantly different between the blood and tissue. T cell PD-1 was blocked (≥98%) in the blood of all patients by the third week of treatment. In the tumor, 5/11 (45%) and 11/14 (79%) patients had T cell surface PD-1 occupance at weeks six and nine, respectively. The proportion of genome copy number alterations and abundance of intratumoral 4-1BB+ PD-1+ CD8 T cells at baseline (P < 0.05), and fold-expansion of intratumoral CD8 T cells from baseline to cycle 2–3 (P < 0.05) were associated with treatment response.

Conclusion

This study provides technical feasibility data for correlative studies. Tissue biopsies provide distinct data from the blood and may predict response to pembrolizumab.

Electronic supplementary material

The online version of this article (10.1186/s40425-019-0541-0) contains supplementary material, which is available to authorized users.

Abstract P6-17-29: Withdrawn

This abstract was withdrawn by the authors.

Citation Format: Veitch ZW, Bedard P, Tang PA, Conway JL, Ribnikar D, Albaba H, King K, Lupichuk S, Cescon D. Withdrawn [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P6-17-29.

Abstract OT3-06-07: A phase I/II dose escalation and expansion study to investigate the safety, pharmacokinetics, pharmacodynamics and clinical activity of GSK525762 in combination with fulvestrant in subjects with ER+ breast cancer

Background:

Advanced or metastatic ER+BC (estrogen receptor positive breast cancer) is an incurable illness that will prove fatal for most afflicted women. Current standards of care include endocrine, targeted, and chemotherapy. Preclinical data suggest that altering the expression of the estrogen receptor (ER) as well as other ER-responsive genes may provide therapeutic benefit for women for whom endocrine therapy alone has proven inadequate. The bromodomain (BRD) and extra-terminal (BET) family of proteins (BRD2, BRD3, BRD4 and BRDT) bind to acetyl-histone residues and epigenetically control transcription of genes driving cell survival and proliferation. BET proteins have been implicated in carcinogenesis and treatment resistance in multiple tumors including ER+BC, and are a novel target for therapy in breast cancer. GSK525762 is a pan-BET inhibitor that has shown strong synergistic activity with fulvestrant in killing ER+BC cells in vitro and in xenograft models. The combination of BET agents with endocrine therapy may provide therapeutic benefit and restore sensitivity to ER targeting agents like fulvestrant.

Trial Design & Specific Aims:

This study is a Phase I/II dose-escalation, expansion (Phase I) and randomized control (Phase II) study with oral administration of GSK525762 in combination with fulvestrant in advanced or metastatic ER+BC subjects, whose disease has progressed on prior treatment with at least one line of endocrine therapy.

Phase I of the study is designed as parallel single arms to determine a recommended Phase 2 dose (RP2D) based on safety, tolerability, pharmacokinetic, and efficacy profiles in two distinct populations of ER+ breast cancer:

Subjects with disease that relapsed during treatment or within 12 months of adjuvant therapy with an AI, OR disease that progressed during treatment with an AI for advanced/metastatic disease.

OR

Subjects with disease that progressed during treatment with the combination of a CDK4/6 inhibitor plus letrozole for advanced or metastatic disease.

Phase II of the study is a randomized, double-blind, placebo-controlled cohort, designed to evaluate the efficacy of the combination.

Key Eligibility Criteria: Patients must have received &lt;3 lines of systemic anti-cancer therapy (≤1 line of chemo), measurable disease, and PS 0-1.

Statistical Methods: A modified toxicity probability interval (mTPI) design will be used to monitor safety. A Bayesian adaptive design will be used to evaluate efficacy in Phase 1.

Present and Target Accrual: Target enrolment will be ˜300 subjects across ˜50 sites worldwide. To date, 2 subjects have been enrolled.

Contact Information: Elizabeth Cunningham, Elizabeth.A.Cunningham@GSK.com.

NCT02964507

Funding: GSK

Citation Format: Pluard T, Oh SY, Oliveira M, Cescon D, Tan-Chiu E, Wu Y, Carpenter C, Cunningham E, Ballas M, Dhar A, Sparano J. A phase I/II dose escalation and expansion study to investigate the safety, pharmacokinetics, pharmacodynamics and clinical activity of GSK525762 in combination with fulvestrant in subjects with ER+ breast cancer [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr OT3-06-07.

Gene isoforms as expression-based biomarkers predictive of drug response in vitro

Next-generation sequencing technologies have recently been used in pharmacogenomic studies to characterize large panels of cancer cell lines at the genomic and transcriptomic levels. Among these technologies, RNA-sequencing enable profiling of alternatively spliced transcripts. Given the high frequency of mRNA splicing in cancers, linking this feature to drug response will open new avenues of research in biomarker discovery. To identify robust transcriptomic biomarkers for drug response across studies, we develop a meta-analytical framework combining the pharmacological data from two large-scale drug screening datasets. We use an independent pan-cancer pharmacogenomic dataset to test the robustness of our candidate biomarkers across multiple cancer types. We further analyze two independent breast cancer datasets and find that specific isoforms of IGF2BP2, NECTIN4, ITGB6, and KLHDC9 are significantly associated with AZD6244, lapatinib, erlotinib, and paclitaxel, respectively. Our results support isoform expressions as a rich resource for biomarkers predictive of drug response.

CX-5461 is a DNA G-quadruplex stabilizer with selective lethality in BRCA1/2 deficient tumours

G-quadruplex DNAs form four-stranded helical structures and are proposed to play key roles in different cellular processes. Targeting G-quadruplex DNAs for cancer treatment is a very promising prospect. Here, we show that CX-5461 is a G-quadruplex stabilizer, with specific toxicity against BRCA deficiencies in cancer cells and polyclonal patient-derived xenograft models, including tumours resistant to PARP inhibition. Exposure to CX-5461, and its related drug CX-3543, blocks replication forks and induces ssDNA gaps or breaks. The BRCA and NHEJ pathways are required for the repair of CX-5461 and CX-3543-induced DNA damage and failure to do so leads to lethality. These data strengthen the concept of G4 targeting as a therapeutic approach, specifically for targeting HR and NHEJ deficient cancers and other tumours deficient for DNA damage repair. CX-5461 is now in advanced phase I clinical trial for patients with BRCA1/2 deficient tumours (Canadian trial, NCT02719977, opened May 2016).

Abstract P3-09-05: Clinical outcome of patients with advanced triple negative breast cancer with germline and somatic variants in homologous recombination gene

Background: Variants in homologous recombination (HR) genes other than BRCA1/2 may cause a BRCA-like phenotype triple negative breast cancer (TNBC), which includes the sensitivity to platinums and DNA repair inhibitors. Evaluation of HR proficiency may influence the clinical management of TNBC. Our aim was to evaluate germline and somatic HR gene variants in advanced TNBC patients (pts) and clinical outcome.

Methods: Our cohort included advanced TNBC pts unselected for family history or age at diagnosis, enrolled in an institutional molecular screening program (NCT01505400). DNA from matched blood and FFPE tumor samples was assessed using a lab developed next generation sequencing Hereditary Cancer Panel (NGS-HCP) that includes all exons of 52 cancer predisposition genes, with 20 HR genes (Illumina MiSeq/NextSeq, germline coverage 100x, somatic coverage 500x). Medical records were reviewed for clinical outcome, pathology and prior germline BRCA1/2 testing results. All pts consented for research on banked samples and return of pathogenic germline variants was optional. Log rank test was used to determine time from surgery with curative intent to relapse (TTR) and overall survival from diagnosis to death (OS) differences based on presence of HR variants.

Results: We included 32 pts who consented for return of pathogenic germline variants and had sufficient DNA for NGS-HCP analysis. Median age at diagnosis was 45 years (range 21-80). Initial stages at diagnosis were: I (12.5%), II (62.5%), III (19%) and IV (6%). Germline HR variants were detected in 17 pts (53%) with a median number of variants per patient of 1 (range 0-6). Five pts had likely pathogenic or pathogenic variants in HR genes: BRCA1 (2), BRCA2 (1) FANCC (1) and FANCC + BML (1). Another patient had a BRCA1 pathogenic variant previously detected by Multiplex Ligation-dependent Probe Amplification but was not detected by NGS-HCP. 26 variants of unknown significance (VUS) were identified in 13 HR genes, including FANCA (6), FANCF (3) and BRCA1 (3). Only one patient had a somatic HR variant in FANCA not found in the germline. 30 pts (94%) had somatic TP53 variants. Sporadic somatic BRCA1/2 variants were not seen. BRCA1/2 variants present in the tumor were equivalent to those detected in blood of BRCA1/2 carriers. Median (m) TTR was 17 months (range 1-119) and mOS was 49 months (range 8-123). Presence of likely pathogenic or pathogenic germline variants was not associated with TTR (p=0.78) and OS (p=0.23). Presence of germline VUS, likely pathogenic or pathogenic variants also did not correlate with TTR (p=0.72) and OS (p=0.47)

Conclusions: In our cohort of pts with advanced TNBC, 12% had germline pathogenic variants in BRCA1/2, similar to the previously reported rate in early stage TNBC pts. Prevalence of likely pathogenic or pathogenic variants in non-BRCA HR genes was 6%. The presence of germline variants in HR genes was not associated with clinical outcome, however, the number of patients included was small and we had limited power to detect survival differences.Background: Variants in homologous recombination (HR) genes other than BRCA1/2 may cause a BRCA-like phenotype triple negative breast cancer (TNBC), which includes the sensitivity to platinums and DNA repair inhibitors. Evaluation of HR proficiency may influence the clinical management of TNBC. Our aim was to evaluate germline and somatic HR gene variants in advanced TNBC patients (pts) and clinical outcome.

Methods: Our cohort included advanced TNBC pts unselected for family history or age at diagnosis, enrolled in an institutional molecular screening program (NCT01505400). DNA from matched blood and FFPE tumor samples was assessed using a lab developed next generation sequencing Hereditary Cancer Panel (NGS-HCP) that includes all exons of 52 cancer predisposition genes, with 20 HR genes (Illumina MiSeq/NextSeq, germline coverage 100x, somatic coverage 500x). Medical records were reviewed for clinical outcome, pathology and prior germline BRCA1/2 testing results. All pts consented for research on banked samples and return of pathogenic germline variants was optional. Log rank test was used to determine time from surgery with curative intent to relapse (TTR) and overall survival from diagnosis to death (OS) differences based on presence of HR variants.

Results: We included 32 pts who consented for return of pathogenic germline variants and had sufficient DNA for NGS-HCP analysis. Median age at diagnosis was 45 years (range 21-80). Initial stages at diagnosis were: I (12.5%), II (62.5%), III (19%) and IV (6%). Germline HR variants were detected in 17 pts (53%) with a median number of variants per patient of 1 (range 0-6). Five pts had likely pathogenic or pathogenic variants in HR genes: BRCA1 (2), BRCA2 (1) FANCC (1) and FANCC + BML (1). Another patient had a BRCA1 pathogenic variant previously detected by Multiplex Ligation-dependent Probe Amplification but was not detected by NGS-HCP. 26 variants of unknown significance (VUS) were identified in 13 HR genes, including FANCA (6), FANCF (3) and BRCA1 (3). Only one patient had a somatic HR variant in FANCA not found in the germline. 30 pts (94%) had somatic TP53 variants. Sporadic somatic BRCA1/2 variants were not seen. BRCA1/2 variants present in the tumor were equivalent to those detected in blood of BRCA1/2 carriers. Median (m) TTR was 17 months (range 1-119) and mOS was 49 months (range 8-123). Presence of likely pathogenic or pathogenic germline variants was not associated with TTR (p=0.78) and OS (p=0.23). Presence of germline VUS, likely pathogenic or pathogenic variants also did not correlate with TTR (p=0.72) and OS (p=0.47)

Conclusions: In our cohort of pts with advanced TNBC, 12% had germline pathogenic variants in BRCA1/2, similar to the previously reported rate in early stage TNBC pts. Prevalence of likely pathogenic or pathogenic variants in non-BRCA HR genes was 6%. The presence of germline variants in HR genes was not associated with clinical outcome, however, the number of patients included was small and we had limited power to detect survival differences.

Citation Format: Stjepanovic N, Kim RH, Wilson M, Mandilaras V, Berman H, Amir E, Cescon D, Elser C, Randall Armel S, McCuaig J, Volenik A, Demsky R, Chow H, Misyura M, Wang L, Oza AM, Kamel-Reid S, Stockley T, Bedard PL. Clinical outcome of patients with advanced triple negative breast cancer with germline and somatic variants in homologous recombination gene [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P3-09-05.

Association of MDM2 T309G and p53 Arg72Pro polymorphisms and gastroesophageal reflux disease with survival in esophageal adenocarcinoma

BACKGROUND AND AIM

Although gastroesophageal reflux disease (GERD) is a risk factor for esophageal adenocarcinoma (EAC), some patients develop EAC in the absence of GERD. A putative mechanism of reflux-induced tumorigenesis involves disruptions in the p53 pathway. We assessed the interaction of GERD and p53 pathway polymorphisms on EAC prognosis.

METHODS

In a prospective cohort of 358 EAC patients, clinical data (including GERD history and survival) were collected. Germline DNA was genotyped for MDM2 T309G and p53 Arg72Pro. Cox proportional hazards models were used to determine adjusted hazard ratios (AHR) for associations between genotype, GERD, and genotype-GERD interactions with survival.

RESULTS

Compared with other genotypes, MDM2 G/G (median overall survival 21 vs 30 months; P < 0.001) and p53 Pro/Pro (12 vs 30 months; P = 0.004) were associated with shorter survival. When analyzed by GERD, MDM2 G/G was associated with shorter survival in patients without GERD (AHR 3.4, 95% CI 2.0-6.0), but not in patients with GERD (AHR 1.1 [0.7-1.8]); the MDM2-GERD interaction was significant (P = 0.003). A similar trend was seen for p53 Pro/Pro (AHRs 2.5 without GERD vs 1.4 with GERD). Combined analysis of at-risk variants (MDM2 G or p53 Pro), revealed each additional at-risk variant was associated with shorter survival in patients without GERD (AHR 1.6) but not with GERD (AHR 1.0).

CONCLUSIONS

MDM2 G/G and the combination of MDM2 G and p53 Pro were negative prognostic factors for EAC patients without GERD but not for those with GERD. There may be biological differences between GERD positive and GERD negative EAC.

Mule/Huwe1/Arf-BP1 suppresses Ras-driven tumorigenesis by preventing c-Myc/Miz1-mediated down-regulation of p21 and p15

Tumorigenesis results from dysregulation of oncogenes and tumor suppressors that influence cellular proliferation, differentiation, apoptosis, and/or senescence. Many gene products involved in these processes are substrates of the E3 ubiquitin ligase Mule/Huwe1/Arf-BP1 (Mule), but whether Mule acts as an oncogene or tumor suppressor in vivo remains controversial. We generated K14Cre;Mule(flox/flox(y)) (Mule kKO) mice and subjected them to DMBA/PMA-induced skin carcinogenesis, which depends on oncogenic Ras signaling. Mule deficiency resulted in increased penetrance, number, and severity of skin tumors, which could be reversed by concomitant genetic knockout of c-Myc but not by knockout of p53 or p19Arf. Notably, in the absence of Mule, c-Myc/Miz1 transcriptional complexes accumulated, and levels of p21CDKN1A (p21) and p15INK4B (p15) were down-regulated. In vitro, Mule-deficient primary keratinocytes exhibited increased proliferation that could be reversed by Miz1 knockdown. Transfer of Mule-deficient transformed cells to nude mice resulted in enhanced tumor growth that again could be abrogated by Miz1 knockdown. Our data demonstrate in vivo that Mule suppresses Ras-mediated tumorigenesis by preventing an accumulation of c-Myc/Miz1 complexes that mediates p21 and p15 down-regulation.

A risk haplotype in the Solute Carrier Family 22A4/22A5 gene cluster influences phenotypic expression of Crohn's disease

BACKGROUND AND AIMS

Previously, we identified 2 functionally relevant polymorphisms in the SLC22A4 / 22A5 genes at the IBD5 locus that alter gene/protein function and comprise a 2-allele haplotype ( SLC22A -TC) associated with increased risk for Crohn's disease (CD). Here we examine the contribution of this susceptibility haplotype alone and in combination with CARD15 variants to CD subphenotypes and to susceptibility to ulcerative colitis (UC).

METHODS

Phenotype-genotype associations were evaluated in a Canadian cohort including 507 patients with CD, 216 patients with UC, and 352 ethnically matched controls genotyped for SLC22A4 C1672T, SLC22A5 G-207C, and the major CD-associated CARD15 variants.

RESULTS

The SLC22A -TC haplotype was strongly associated ( P < .0001) with CD in the non-Jewish subgroup of this cohort, and the combination of SLC22A -TC homozygosity and one or more of the common CARD15 disease susceptibility alleles engendered a 7.5-fold increase in risk for CD ( P = 9 x 10 -8 ) and a 4.5-fold increase in risk for ileal disease ( P = .001). The risk haplotype showed only a suggestive association with CD in the Jewish subgroup and no association with UC in the cohort or in subgroups stratified by CARD15 genotypes.

CONCLUSIONS

The SLC22A -TC haplotype acts together with CARD15 disease susceptibility alleles to increase risk for CD and ileal disease among CD patients but does not contribute to risk for UC in this Canadian cohort. The association of the SLC22A -TC haplotype and CARD15 alleles with ileal disease suggests that these variants have biologically intertwined effects in the pathogenesis of CD.

Functional variants of OCTN cation transporter genes are associated with Crohn disease

Crohn disease is a chronic, inflammatory disease of the gastrointestinal tract. A locus of approximately 250 kb at 5q31 (IBD5) was previously associated with susceptibility to Crohn disease, as indicated by increased prevalence of a risk haplotype of 11 single-nucleotide polymorphisms among individuals with Crohn disease, but the pathogenic lesion in the region has not yet been identified. We report here that two variants in the organic cation transporter cluster at 5q31 (a missense substitution in SLC22A4 and a G-->C transversion in the SLC22A5 promoter) form a haplotype associated with susceptibility to Crohn disease. These variants alter transcription and transporter functions of the organic cation transporters and interact with variants in another gene associated with Crohn disease, CARD15, to increase risk of Crohn disease. These results suggest that SLC22A4, SLC22A5 and CARD15 act in a common pathogenic pathway to cause Crohn disease.