Abstract PD2-02: SFX-01 targets Wnt signalling to inhibit stem-like cells in breast cancer patient-derived xenograft tumours

Background: SFX-01 is a novel therapeutic comprising synthetic sulforaphane (SFN) stabilised within a-cyclodextrin. Breast cancer stem-like cells (CSCs) have been identified in all molecular subtypes and are likely drivers of breast cancer metastasis and treatment resistance. We recently established that CSC activity in ER+ BC, represent a source of therapeutic resistance (Simões et al, Cell Reports, 2015).

Material and methods: We investigated SFX-01 effects on breast CSC activity using mammosphere formation efficiency (MFE) and aldehyde dehydrogenase (ALDH) activity using the ALDEFLUOR assay in patient samples and patient-derived xenograft (PDX) tumours. Cells from primary (n=12) and metastatic (n=15) samples were treated with SFX-01 (5 μM) or vehicle control.Using a 2 or 8 week in vivo treatment, early (HBCx34) and metastatic (BB3RC31) ER+ PDX tumours were treated with SFX-01 (300mg/Kg/day) alone or in combination with tamoxifen (TAM, 10 mg/kg/day) or fulvestrant (FULV, 200 mg/kg/week). Tumours were dissociated and MFE and ALDH activity assessed.

Results: SFX-01 in vitro reduced MFE of both primary (0.19%±0.02 vs control 0.52%±0.06: p<0.001) and metastatic patient samples (0.43±0.04 vs control 0.93%±0.07: p<0.001). SFX-01 treatment in vivo for 2 weeks reduced MFE of HBCx34 (0.35%±0.03 vs control 0.64%±0.09; p<0.01) and BB3RC31 (0.78%±0.04 vs control 0.89%±0.06: p<0.05) and also ALDH activity of HBCx34 (3%±0.6 vs control 6.3%±0.4: p<0.01) and BB3RC31 (1%±0.2 vs control 3%±0.6: p<0.05). TAM and FULV increased MFE and ALDH activity after 2 weeks of treatment in vivo, which was abrogated by combination with SFX-01; for example HBCx34 MFE with TAM alone: 0.81%±0.07 vs TAM+SFX-01: 0.34%±0.02 (p<0.01) and ALDH+ with TAM alone 10%±0.4 vs TAM+SFX 4.2%±0.4 (p<0.01). TAM+SFX-01 suppressed tumour growth at 8 weeks vs TAM alone in HBCx34 but not BB3RC31. FULV treatment maintained tumour growth suppression at 8 weeks and no additive effect was seen with SFX-01, although MFE and ALDH activity were suppressed. Mechanistically, SFX-01 potently inhibited the canonical Wnt pathway in MCF-7 cells and their endocrine-resistant derivatives and we are currently exploring SFX-01 activity on other CSC regulatory pathways.

SFX-01 has been shown to be well tolerated in SAD and MAD studies in normal volunteers and clinical studies designed to test tolerability and efficacy in combination with the three major classes of endocrine therapy (AI, TAM and FULV) in advanced BC will begin in Q4 2016.

Conclusions: Our data demonstrate the potential of SFX-01 for clinically meaningful improvements to endocrine therapy in ER+ breast cancer by reversing CSC mediated resistance.

Citation Format: Howell SJ, Simoes BM, Alferez D, Eyre R, Spence K, Santiago-Gomez A, Sarmiento-Castro A, Tanaka I, Howat D, Clarke RB. SFX-01 targets Wnt signalling to inhibit stem-like cells in breast cancer patient-derived xenograft tumours [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 PD2-02.

Abstract P5-05-03: Progesterone receptor antagonists as inhibitors of breast cancer stem cell activity

Background: Tamoxifen has become the standard of care for premenopausal women with hormone receptor positive breast cancer (BC). However, resistance to Tamoxifen therapy remains a major clinical problem and we have evidence that cancer stem cells (CSCs) may play a role in recurrence in these patients. The progesterone receptor (PR) is a potential therapeutic target in BC but development of steroidal PR antagonists (PRAs) has been halted due to toxicity issues, despite evidence of activity. Recent reports have linked PR activity to the expansion of adult mammary gland stem cells through paracrine effectors such as RANK-L.

Methods: To investigate the effects of PR antagonism on CSCs, we have tested 2 non-steroidal PRAs; onapristone (Schering AG/Arno Therapeutics) and AZPRA (AstraZeneca) in 2 hormone receptor positive BC cell lines (MCF-7 & T47D) and 8 patient-derived samples (PDS; from malignant pleural effusions and ascitic fluid), using a low adherence mammosphere assay. Western and gene expression array analysis of PDS samples were performed to identify predictive biomarkers.

Results: In the presence of 10nM P4 AZPRA inhibited mammosphere forming efficiency (MFE) in MCF-7 cells by 32% (p<0.0001) and in T47D by 21% (p<0.0001). Similar results were seen with onapristone (34% inhibition in MCF-7 (p<0.002) and 34% in T47D cells (p<0.0002). AZPRA or onapristone significantly reduced MFE in 7 of 8 PDS. Tamoxifen affected MFE in 4/6 PDS samples. In 5 of 7 PDS tested additive effects were seen when AZPRA was combined with tamoxifen (>80% reduction in MFE; p<0.001). A similar effect was seen with onapristone (>70% reduction in MFE (p<0.05)). Data from Western analysis of PR A and B isoforms and gene expression analysis of PDS samples will be presented at the conference.

Conclusions: Preliminary data on PR inhibition presented here support the rationale of administration of PRA in the clinic but predictive biomarkers are required to identify which patients are likely to benefit. Combination of PRA with current anti-oestrogen therapies such as Tamoxifen may be a way of overcoming resistance mechanisms by targeting CSCs.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P5-05-03.

To best measure cell proliferation in samples from the intestine

Arrangement of the intestinal cell lining, as it is, into distinct anatomically defined zones where proliferation is confined to the crypts, makes it an ideal tissue to study growth control mechanisms. While many methods have been used to quantify cell proliferation in the gut, several of them have severe limitations and others (although potentially better) have been misused and misinterpreted. Here, correct use and interpretation of labelling studies will be described as will a well established alternative method that provides equivalent results for one-sixth of the effort.

Inhibiting vascular endothelial growth factor receptor-2 signaling reduces tumor burden in the ApcMin/+ mouse model of early intestinal cancer

The Apc(Min/+) mouse model is a clinically relevant model of early intestinal cancer. We used AZD2171, an oral, highly potent and selective vascular endothelial growth factor (VEGF) signaling inhibitor, to investigate the role of VEGF receptor-2 (VEGFR-2) signaling in adenoma development and growth in Apc(Min/+) mice. AZD2171 (5 mg/kg body wt/day) was administered once daily for 28 days to 6-week-old (early-intervention) or 10-week-old (late intervention) mice. In the early-intervention study, AZD2171 reduced the number of macroscopic polyps in the small bowel and colon. Macropolyp diameter was lower in the small bowel, but remained unchanged in the colon. In animals receiving AZD2171, microscopic evaluation of the small intestine showed a significant reduction in the number of larger lesions. In the late-intervention study, AZD2171 treatment reduced macropolyp diameter (but not number) in the small intestine. Microscopic analysis revealed that AZD2171 significantly reduced the number of larger micropolyps in the small bowel, with no large micropolyps present in the colon. AZD2171 treatment had no effect on microvessel density or localization of beta-catenin staining in adenomas or non-tumor intestinal tissue, but significantly reduced the number of cells expressing VEGFR-2 mRNA. In conclusion, the effects of AZD2171 in the small intestine of Apc(Min/+) mice are consistent with an antiangiogenic mechanism of action, limiting growth of adenomas to < or =1 mm. These data also suggest that an early step in adenoma development may depend on VEGFR-2 signaling. Together, these results indicate that VEGFR-2 signaling may play key roles in the development and progression of intestinal adenomas.

Effects of gravity, hypergravity and microgravity on vestibular neurones of the crab

Recordings were made from identified balancing system interneurones using implanted electrodes in crabs oscillated at 0.3 Hz during bouts of Parabolic flight. Repeatable non stabilized patterns of response firing were seen in head up and head down interneurones. During the hypergravity phases, the ratio of firing frequencies in the two directional categories of interneurones was altered showing that hypergravity produced effects normally seen during tilting of the crab, implying greater bending of the sensory thread hairs. During microgravity, firing levels remained low and constant or changed slowly towards initial firing levels.