Focal adhesion kinase is required for intestinal regeneration and tumorigenesis downstream of Wnt/c-Myc signaling

The intestinal epithelium has a remarkable capacity to regenerate after injury and DNA damage. Here, we show that the integrin effector protein Focal Adhesion Kinase (FAK) is dispensable for normal intestinal homeostasis and DNA damage signaling, but is essential for intestinal regeneration following DNA damage. Given Wnt/c-Myc signaling is activated following intestinal regeneration, we investigated the functional importance of FAK following deletion of the Apc tumor suppressor protein within the intestinal epithelium. Following Apc loss, FAK expression increased in a c-Myc-dependent manner. Codeletion of Apc and Fak strongly reduced proliferation normally induced following Apc loss, and this was associated with reduced levels of phospho-Akt and suppression of intestinal tumorigenesis in Apc heterozygous mice. Thus, FAK is required downstream of Wnt Signaling, for Akt/mTOR activation, intestinal regeneration, and tumorigenesis. Importantly, this work suggests that FAK inhibitors may suppress tumorigenesis in patients at high risk of developing colorectal cancer.

Involvement of focal adhesion kinase in cellular invasion of head and neck squamous cell carcinomas via regulation of MMP-2 expression

Focal adhesion kinase (FAK) is considered intimately involved in cancer progression. Our previous research has demonstrated that overexpression of FAK is an early and frequent event in squamous cell carcinomas of the supraglottic larynx, and it is associated with the presence of metastases in cervical lymph nodes. The purpose of this study was to examine the functional role of FAK in the progression of head and neck squamous cell carcinomas (HNSCC). To this end, expression of FAK-related nonkinase (FRNK) or small interfering RNA (siRNA) against FAK was used to disrupt the FAK-induced signal transduction pathways in the HNSCC-derived SCC40 and SCC38 cell lines. Similar phenotypic effects were observed with the two methodological approaches in both cell lines. Decreased cell attachment, motility and invasion were induced by FRNK and FAK siRNA, whereas cell proliferation was not impaired. In addition, increased cell invasion was observed upon FAK overexpression in SCC cells. FRNK expression resulted in a downregulation of MMP-2 and MMP-9 expression. Interestingly, MMP-2 overexpression in FRNK-expressing cells rescued FRNK inhibition of cell invasion. This is the first demonstration of a direct rescue of impaired cell invasion by the re-expression of MMP-2 in a tumour cell type with decreased expression of functional FAK. Collectively, these data reported here support the conclusion that FAK enhances invasion of HNSCC by promoting both increased cell motility and MMP-2 production, thus providing new insights into possible therapeutic intervention strategies.

Investigation of cellular uptake mechanism of functionalised gold nanoparticles into breast cancer using SERS

Gold nanoparticles (AuNPs) are widely used in various applications such as cancer imaging and drug delivery. The functionalisation of AuNPs has been shown to affect their cellular internalisation, accumulation and targeting efficiency. The mechanism of cellular uptake of functionalised AuNPs by different cancer cells is not well understood. Therefore, a detailed understanding of the molecular processes is necessary to improve AuNPs for their selective uptake and fate in specific cellular systems. This knowledge can greatly help in designing nanotags with higher cellular uptake for more selective and specific targeting capabilities with less off-target effects. Here, we demonstrate for the first time a straightforward and non-destructive 3D surface enhanced Raman spectroscopy (SERS) imaging approach to track the cellular uptake and localisation of AuNPs functionalised with an anti-ERα (estrogen receptor alpha) antibody in MCF-7 ERα-positive human breast cancer cells under different conditions including temperature and dynamin inhibition. 3D SERS enabled information rich monitoring of the intracellular internalisation of the SERS nanotags. It was found that ERα-AuNPs were internalised by MCF-7 cells in a temperature-dependent manner suggesting an active endocytosis-dependent mechanism. 3D SERS cell mapping also indicated that the nanotags entered MCF-7 cells using dynamin dependent endocytosis, since dynamin inhibition resulted in the SERS signal being obtained from, or close to, the cell surface rather than inside the cells. Finally, ERα-AuNPs were found to enter MCF-7 cells using an ERα receptor-mediated endocytosis process. This study addresses the role of functionalisation of SERS nanotags in biological environments and highlights the benefits of using 3D SERS for the investigation of cellular uptake processes.

Phosphorylated c-Src in the nucleus is associated with improved patient outcome in ER-positive breast cancer

Elevated c-Src protein expression has been shown in breast cancer and in vitro evidence suggests a role in endocrine resistance. To investigate whether c-Src is involved in endocrine resistance, we examined the expression of both total and activated c-Src in human breast cancer specimens from a cohort of oestrogen receptor (ER)-positive tamoxifen-treated breast cancer patients. Tissue microarray technology was employed to analyse 262 tumour specimens taken before tamoxifen treatment. Immunohistochemistry using total c-Src and activated c-Src antibodies was performed. Kaplan–Meier survival curves were constructed and log-rank test were performed. High level of nuclear activated Src was significantly associated with improved overall survival (P=0.047) and lower recurrence rates on tamoxifen (P=0.02). Improved patient outcome was only seen with activated Src in the nucleus. Nuclear activated Src expression was significantly associated with node-negative disease and a lower NPI (P<0.05). On subgroup analysis, only ER-positive/progesterone receptor (PgR)-positive tumours were associated with improved survival (P=0.004). This shows that c-Src activity is increased in breast cancer and that activated Src within the nucleus of ER-positive tumours predicts an improved outcome. In ER/PgR-positive disease, activated Src kinase does not appear to be involved in de novo endocrine resistance. Further study is required in ER-negative breast cancer as this may represent a cohort in which it is associated with poor outcome.

In vivo imaging of the tumor and its associated microenvironment using combined CARS / 2-photon microscopy

The use of confocal and multi-photon microscopy for intra-vital cancer imaging has impacted on our understanding of cancer cell behavior and interaction with the surrounding tumor microenvironment in vivo. However, many studies to-date rely on the use fluorescent dyes or genetically encoded probes that enable visualization of a structure or cell population of interest, but do not illuminate the complexity of the surrounding tumor microenvironment. Here, we show that multi-modal microscopy combining 2-photon fluorescence with CARS can begin to address this deficit, enabling detailed imaging of the tumor niche without the need for additional labeling. This can be performed on live tumor-bearing animals through optical observation windows, permitting real-time and longitudinal imaging of dynamic processes within the tumor niche.

Novel roles of PRK1 and PRK2 in cilia and cancer biology

PRK1 and PRK2 are two closely related AGC-family serine/threonine protein kinases. Here we demonstrate novel roles for them at cilia and in cancer biology. In both instances serum withdrawal leads to increased activating PRK1 and PRK2 phosphorylation (pPRK1/pPRK2) and their depletion results in reduced spheroid growth. pPRK1/pPRK2 localise to the transition zone of cilia and their co-depletion results in reduced cilia size, impaired planer polarity and impaired cilia associated signalling. High PRK2 (but not PRK1) expression correlates with poor outcome in patients with basal-like/Triple Negative (TN) Breast Cancer (BC) where there is also higher expression relative to other BC tumour subtypes. In agreement, depletion of PRK1 and PRK2 in mouse TNBC cells, or CRISPR/Cas9 mediated deletion of PRK2 alone, significantly reduces cell proliferation and spheroid growth. Finally proteomic analysis to identify PRK2 binding partners in mouse TNBC cells revealed proteins that are important for both cilia and BC biology. Taken together these data demonstrate novel roles for PRK1 and PRK2 at cilia and in BC biology and in the case of PRK2 in particular, identifies it as a novel TNBC therapeutic target.

MYC sensitises cells to apoptosis by driving energetic demand

The MYC oncogene is a potent driver of growth and proliferation but also sensitises cells to apoptosis, which limits its oncogenic potential. MYC induces several biosynthetic programmes and primary cells overexpressing MYC are highly sensitive to glutamine withdrawal suggesting that MYC-induced sensitisation to apoptosis may be due to imbalance of metabolic/energetic supply and demand. Here we show that MYC elevates global transcription and translation, even in the absence of glutamine, revealing metabolic demand without corresponding supply. Glutamine withdrawal from MRC-5 fibroblasts depletes key tricarboxylic acid (TCA) cycle metabolites and, in combination with MYC activation, leads to AMP accumulation and nucleotide catabolism indicative of energetic stress. Further analyses reveal that glutamine supports viability through TCA cycle energetics rather than asparagine biosynthesis and that TCA cycle inhibition confers tumour suppression on MYC-driven lymphoma in vivo. In summary, glutamine supports the viability of MYC-overexpressing cells through an energetic rather than a biosynthetic mechanism.

Abstract 3326: Uncovering the molecular mechanisms which predict sensitivity to a novel src kinase inhibitor NXP900 to inform personalized healthcare strategies

We have previously described the discovery of a highly potent, selective and orally bioavailable Src kinase inhibitor NXP900 with a unique binding mode relative to other Src inhibitors under clinical development or approved (Temps et al 2021). This unique binding mode locks SRC in its native inactive conformation, thereby inhibiting both enzymatic and scaffolding functions. Also, in contrast to other Src inhibitors in the clinic, NXP900 exhibits a unique target selectivity profile with 1000 fold selectivity for Src over Abl kinase. The aim of this current study was to perform broad cancer cell line panel screening to inform disease positioning and identify predictive biomarkers of sensitivity for this novel class of Src kinase inhibitor. We describe the results of extensive cancer cell line panel profiling across a suite of 2-dimensional(D) and 3-D in vitro cell viability and high content phenotypic profiling assays that has revealed clear patterns of cell line sensitivity and insensitivity. Among the most sensitive cell line subtypes are, squamous cell carcinoma, Arid1A mutant ovarian clear cell carcinoma and subtypes of breast luminal A and triple negative breast cancer cell lines. HER2+ breast cancer lines appear insensitive to NXP900 indicating HER2 as a potential driver of resistance to NXP900. Further in-depth bioinformatic analysis of genetic and transcriptomic profiles of sensitive cell lines has identified putative biomarkers to support patient selection and personalized healthcare strategies. These studies demonstrate the identification of cancer cell lines which exhibit high sensitivity to NXP900 and which can be grouped into discrete molecular subtypes based on gene mutation status, transcriptomics and histotype. Our result provide an indication of patient subgroups which may exhibit optimal therapeutic response to NXP900 and provide data to guide further preclinical, biomarker and clinical development. Temps C et al., Cancer Res. 2021 Nov 1;81(21):5438-5450. doi: 10.1158/0008-5472.CAN-21-0613.

Citation Format: Neil Carragher, Rebecca Hughes, Valerie Brunton, Asier Unciti-broceta, Iñigo Lanzagorta-Calvillo, Carolin Temps, Enrique Poradosu. Uncovering the molecular mechanisms which predict sensitivity to a novel src kinase inhibitor NXP900 to inform personalized healthcare strategies [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3326.

Abstract 4453: Development and characterisation of AZD-8931-resistant HER-2 positive breast cancer cells

The introduction of HER-2 directed therapies has revolutionised the management of both early and advanced HER-2 positive breast cancer. However, despite significant improvements in treatment outcomes, both inherent and acquired resistance are frequently encountered problems. Emerging evidence from early phase neo-adjuvant clinical trials, such as Neo-sphere and Neo-ALTTO, suggests that targeting multiple members of the Human epidermal growth factor receptor (HER) family is more efficacious than single target inhibition. AZD 8931 is a novel equipotent reversible tyrosine kinase inhibitor of EGFR, HER-2 and HER-3 signalling with proven pre-clinical efficacy in breast, head and neck and non-small cell lung cancers {1}.

To investigate potential mechanisms of acquired resistance to AZD-8931, HER-2 amplified SKBR-3 breast cancer cells were rendered resistant by culture with escalating doses of drug. Resistant and parental cell lines were phenotypically distinct with resistance being associated with greater cell spreading and increased cell density. Cross resistance to lapatinib, a reversible dual EGFR/HER 2 tyrosine kinase inhibitor, was demonstrated with an over 50 fold increase in IC50. Signalling changes associated with a resistant phenotype were explored with a combination of Reverse Phase Protein Array (RPPA) and western blotting. Following drug treatment, resistant cells still displayed a dose-dependent reduction in phospho HER-2 (Tyr 1248)/EGFR (Tyr 1173). However, constitutive activation of the HER 3 pathway resulted in persistent downstream signalling via the PI3K/AKT pathway and increased cell survival.

Tumorigenesis in the MMTV-Nic model is driven by mammary-specific expression of a constitutively active HER 2 transgene {2}. This model has been crossed with a strain with a floxed PTEN allele {2} and studies are currently under way to explore the role of PTEN in AZD-8931 resistance.

Citation Format: Helen Creedon, Morwenna Muir, Larry Hayward, Valerie Brunton. Development and characterisation of AZD-8931-resistant HER-2 positive breast cancer cells. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4453. doi:10.1158/1538-7445.AM2013-4453

Abstract PR13: The canonical Wnt pathway participates in anchorage-independent growth in a subset of heterogeneous tumor cells derived from a single murine pancreatic tumor

Pancreatic adenocarcinoma is a difficult cancer to treat with poor response rates to current therapies. Using a mouse model of pancreatic adenocarcinoma driven by endogenous expression of KRASG12D and p53R172H, we isolated heterogeneous tumor cell clones from a single tumor. Each of the cell clones has a unique genetic and protein expression signature, and they proliferate at different rates in vitro. Notably, only some of them are able to grow into colonies under anchorage-independent (AI) condition. We found that clones which can undergo AI growth have significantly higher phospho-ERK levels than the others, and the MEK inhibitors PD184352 and UO126 can suppress only some AI growth. We therefore looked for additional drivers of this cancer-associated AI growth and discovered that the canonical Wnt pathway, indicated by high transcription levels of Axin2 and Lgr5, is associated with AI growth in the pancreatic cancer cell clones that are less sensitive to the MEK inhibitors. In addition, two tankyrase inhibitors, XAV939 and IWR1, which stabilize Axin1 and enhance β-catenin degradation, inhibit AI growth in Wntactive cells, but not in ERK-dependent cells. Both tankyrase inhibitors downregulate Wnt-dependent Axin2 and Lgr5 transcription, without affecting phospho-ERK levels. Importantly, knockdown of β-catenin also impairs anchorage-independent growth only in Wnt-active cells. Thus, we have demonstrated for the first time that the canonical Wnt pathway is activated and contributes to AI growth in subclones of pancreatic cancer cells downstream of KRASG12D and p53R172H, and that Axin2 and Lgr5, but not all classical Wnt target genes (for example c-Myc), are involved. Hence, targeting Wnt in pancreatic cancer may be a viable option in treating KRAS- and p53-driven pancreatic cancer, but will probably need to be combined with multiple pathway inhibitors to deal with tumor heterogeneity.

This abstract is also presented as Poster A46.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the Second AACR International Conference on Frontiers in Basic Cancer Research; 2011 Sep 14-18; San Francisco, CA. Philadelphia (PA): AACR; Cancer Res 2011;71(18 Suppl):Abstract nr PR13.

Growth inhibition of gastric cancer cell lines by the tyrphostin RG13022 and its effects on intracellular signalling

Overexpression of EGFr and c-erbB-2 is related to poor prognosis in a variety of cancers including gastric cancer. Thus: the ability to modulate the functional activity of these receptors is an attractive target for diagnostic intervention. In this study we examined the effect of a well characterised tyrosine kinase inhibitor (RG13022) on the cellular proliferation and EGF activated tyrosine kinase signalling pathway of two primary gastric cell lines: MKN45 and N87. RG13022 has a dose dependent, antiproliferative effect on both gastric cell lines when grown either in serum-free conditions or in the presence of FCS. Western blotting revealed RG13022 caused an inhibition of EGF stimulated tyrosine phosphorylation of EGFr in A431 cells and both EGFr and c-erbB-2 in MKN45 cells. No clear modulation of EGFr or c-erbB-2 phosphorylation was observed in N87 cells. In both A431 cells and N87 cells (which overexpress EGFr and c-erbB-2 respectively) exposed to EGF, MAP2 kinase immunoblot analysis resulted in the detection of a second protein band with reduced migration in SDS-PAGE. In N87 cells, this protein appeared to co-mi,orate with a strongly tyrosine phosphorylated protein, which suggests that it is a hyper-phosphorylated form of MAP2 kinase. However, treatment with RG13022, whilst inhibiting phosphorylation of this protein, did not prevent a shift in gel mobility (suggestive of activation) of MAP2 kinase in response to EGF. These findings demonstrate that the tyrphostin RG13022 inhibits cell proliferation of two primary gastric cancer cell lines. Investigation of intracellular signalling pathways suggests that alterations in intracellular signalling are responsible for the actions of RG 13022 in these cells. The biochemical analysis revealed that in N87 and A431, cells which overexpress c-erbB-2 and EGFr respectively, the tyrphostin affects the MAP2 kinase immunoreactivity and migration on SDS gels but fails to affect this protein in the MKN45 cell line. This data questions the usefulness of MAP2 kinase gel shift assays as markers of activation but supports the further development of tyrosine kinase inhibitors as potential inhibitors of gastric tumour proliferation.

Activated c-Src (Y215) kinase expression predicts for early relapse on tamoxifen in human breast cancer

Abstract #3025

Recent studies have demonstrated activation of the non-receptor tyrosine kinase c-Src in tamoxifen resistant breast cancer cell lines, which when treated with Src inhibitors demonstrate a reduction in motility and invasiveness. However, there are little published translational studies confirming a role for c-Src in tamoxifen resistance in vivo. We aim to determine if activated c-Src expression correlates clinically with increased recurrence on tamoxifen.&#x2028; Methods&#x2028; Tissue microarrays were constructed from a patient cohort of 402 Tamoxifen treated ER positive patients. Immunohistochemistry was performed using commercially available antibodies to Total Src as well as to activated (phosphorylated) c-Src at 2 sites (Y416 and Y215) (pSrc416 and pSrc215 respectively). Expression was assessed by 2 independent scorers (weighted histoscore method). HER1-3 status and expression of membranous phosphorylated ER (sites serine 118 and 167) had previously been determined. All statistical calculations were performed using SPSS 15, including Kaplan-Meier life table analysis with log rank testing of differences in breast cancer related relapse whilst on tamoxifen.&#x2028; Results&#x2028; Membranous pSrc215 was observed in 20.3% of the cases but was more frequently observed in the cytoplasm (85.9%) and nucleus (90.5%). Overexpression of cytoplasmic pSrc215 was associated with an earlier time to recurrence (p = 0.037).&#x2028; &#x2028; Cox regression analysis confirmed this to be independent of grade, nodal and HER1-3 status (p=0.028, HR 3.17 (1.14–8.85)). Cytoplasmic pSrc215 was also strongly correlated with membranous phospho-ER, EGFR and HER3 status (Mann Whitney; p&lt;0.001, p=0.026, p&lt;0.001 respectively). Membranous and nuclear pSrc215 staining were not associated with time to relapse.&#x2028; Over expression of Total Src and pSrc416 did not predict for relapse.&#x2028; Discussion&#x2028; Our findings provide support to in vitro studies linking c-Src with tamoxifen resistance. The phosphorylation site pSrc215 is a putative site of activation by HER2 and PGFR resulting in up to 50 fold activation of Src in vitro. The correlations demonstrated with HER status and membranous ER lead us to speculate that this interplay between non genomic ER and Src activation may provide a mechanism for the lack of response to tamoxifen in these patients.&#x2028; Further studies are required to determine if activated pSrc215 represents activated c-Src alone or may also represent activation of other Src family members as the Y416 and Y215 sequences are highly conserved amongst the Src kinases with homologous activation sites. If confirmed, future use of novel combination therapies with Src inhibitors may have an important role in combating tamoxifen resistance.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 3025.