TANGO1 inhibitors reduce collagen secretion and limit tissue scarring

Uncontrolled secretion of ECM proteins, such as collagen, can lead to excessive scarring and fibrosis and compromise tissue function. Despite the widespread occurrence of fibrotic diseases and scarring, effective therapies are lacking. A promising approach would be to limit the amount of collagen released from hyperactive fibroblasts. We have designed membrane permeant peptide inhibitors that specifically target the primary interface between TANGO1 and cTAGE5, an interaction that is required for collagen export from endoplasmic reticulum exit sites (ERES). Application of the peptide inhibitors leads to reduced TANGO1 and cTAGE5 protein levels and a corresponding inhibition in the secretion of several ECM components, including collagens. Peptide inhibitor treatment in zebrafish results in altered tissue architecture and reduced granulation tissue formation during cutaneous wound healing. The inhibitors reduce secretion of several ECM proteins, including collagens, fibrillin and fibronectin in human dermal fibroblasts and in cells obtained from patients with a generalized fibrotic disease (scleroderma). Taken together, targeted interference of the TANGO1-cTAGE5 binding interface could enable therapeutic modulation of ERES function in ECM hypersecretion, during wound healing and fibrotic processes.

Pathophysiology of systemic sclerosis (scleroderma)

Systemic sclerosis (scleroderma) is an autoimmune-triggered chronic fibrosing disease that affects the skin and many other organs. Its pathophysiology is complex and involves an early endothelial damage, an inflammatory infiltrate and a resulting fibrotic reaction. Based on a predisposing genetic background, an altered balance of the acquired and the innate immune system leads to the release of many cytokines and chemokines as well as autoantibodies, which induce the activation of fibroblasts with the formation of myofibroblasts and the deposition of a stiff and rigid connective tissue. A curative treatment is still not available but remarkable progress has been made in the management of organ complications. In addition, several breakthroughs in the pathophysiology have led to new therapeutic concepts. Based on these, many new compounds have been developed during the last years, which target these different pathways and offer specific therapeutic approaches.

Abstract P5-14-06: Towards breast cancer prevention through reduced breast density: Suppressive effects of tamoxifen on normal breast epithelial cells

Background: Breast density is positively associated with risk of breast cancer and the local microenvironment in the normal breast is known to significantly impact breast cancer initiation and further progression. The selective estrogen receptor modulator tamoxifen, with beneficial clinical effects on breast cancer recurrence, has also been shown to reduce mammographic density potentially explaining the primary preventive effects of tamoxifen. Still, important gaps persist regarding the cellular and molecular basis of how tamoxifen modifies breast density and subsequently breast cancer risk.

Purpose: To investigate the impact by tamoxifen on normal human breast epithelial cells (MCF-10A) with the additional ambition to mimic variations in breast density on the cellular level.

Experimental design: Effects of tamoxifen on MCF-10A cells at different cellular densities were evaluated in vitro. Flow cytometry and the sulforhodamine-B assay were used to assess cell cycle distribution and proliferation. Cell adhesion to extracellular matrix proteins was analyzed using hexosaminidase assay. Modulation of integrin receptor levels was determined by Western immunoblotting.

Results: Tamoxifen exposure resulted in impaired cell cycle progression of human breast epithelial cells with a dose-dependent G2/M-phase arrest and reduced cell proliferation. Irrespective of tamoxifen treatment, the percent cellular adhesion to fibronectin and collagen type I by MCF-10A cells was significantly greater in high-density models compared to low-density models. Following tamoxifen treatment the adhesion was reduced in all density models. Consistent with the tamoxifen-induced lower adhesion, the integrin α1 and β3 levels were reduced in a dose-dependent way.

Conclusion: These data support the hypothesis that tamoxifen affects the normal breast epithelium and its adhesion capacity, which may contribute to the clinically observed decrease in breast density and a potential reduced risk of breast tumor establishment.

Citation Format: Rosendahl AH, Puig Blasco L, Borgquist S. Towards breast cancer prevention through reduced breast density: Suppressive effects of tamoxifen on normal breast epithelial cells [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 P5-14-06.

Hypoxia-inducible factor prolyl-4-hydroxylase-1 is a convergent point in the reciprocal negative regulation of NF-κB and p53 signaling pathways

Hypoxia-inducible factor 1α (HIF1α) induces the expression of several hundred genes in hypoxia aiming at restoration of oxygen homeostasis. HIF prolyl-4-hydroxylases (HIF-P4Hs) regulate the stability of HIF1α in an oxygen-dependent manner. Hypoxia is a common feature in inflammation and cancer and the HIF pathway is closely linked with the inflammatory NF-κB and tumor suppressor p53 pathways. Here we show that genetic inactivation or chemical inhibition of HIF-P4H-1 leads to downregulation of proinflammatory genes, while proapoptotic genes are upregulated. HIF-P4H-1 inactivation reduces the inflammatory response under LPS stimulus in vitro and in an acute skin inflammation model in vivo. Furthermore, HIF-P4H-1 inactivation increases p53 activity and stability and hydroxylation of proline 142 in p53 has an important role in this regulation. Altogether, our data suggest that HIF-P4H-1 inhibition may be a promising therapeutic candidate for inflammatory diseases and cancer, enhancing the reciprocal negative regulation of the NF-κB and p53 pathways.

Abstract P4-03-15: Joint influence by paracrine adipocyte signals and metabolic conditions on breast cancer

Background: The growing global population of overweight and obese people represents a pressing public health concern. A higher percentage of body fat is linked to an altered metabolic state and an increased risk of chronic metabolic disorders and cancer. Although, the mechanistic explanations for how obesity affects the development, progression and prognosis of cancer is incompletely mapped.

Purpose: To investigate the joint influence by adipocytes and metabolic pressure on breast cancer cell expansion.

Experimental Design: In vitro differentiated 3T3-L1 adipocytes were exposed to metabolic glucoselow/high and insulinlow/high pressure in order to mimic normal, pre-diabetic, overt diabetic and late diabetic conditions. Adipocyte-conditioned medium was collected and paracrine effects by adipocyte-derived factors on estrogen receptor (ER)-positive (T47D, MCF-7) and ER-negative (MDA-MB-231) breast cancer cell proliferation, molecular adaptations, and cell motility were subsequently analyzed using sulforhodamine B, Western immunoblotting and migration assays.

Results: Under normal metabolic conditions, adipocytes stimulated the growth of ER+ (1.1-2.0-fold; P<0.001) and to a greater extent, ER- breast cancer cells (3.1-fold; P<0.001), compared with controls. The joint effects by adipocyte paracrine signals and higher metabolic pressure (overt or late diabetic conditions), further enhanced the proliferative response in both ER+ and ER- cells (1.3-3.5-fold; P<0.01), compared with controls. Furthermore, adipocyte-derived factors induced morphological changes, protrusion extensions and cell migration in the low invasive T47D cells. Additional acquisition of molecular epithelial-mesenchymal transition features were observed in breast cancer cells following co-culturing with adipocyte-derived factors.

Conclusion: These study results support the hypothesis that paracrine signals by adipocytes significantly stimulate the proliferation and induction of a more motile phenotype of human breast cancer cells, which is further enhanced under obesity-associated metabolic conditions.

Citation Format: Rosendahl AH, Bergqvist M, Lettiero B, Kimbung S, Borgquist S. Joint influence by paracrine adipocyte signals and metabolic conditions on breast cancer [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 P4-03-15.

Abstract P2-07-03: Insulin and breast cancer risk: Novel insights from mammographic density analyses

Background: Insulin has been suspected to influence breast cancer risk because of its mitogenic effects and impact on sex hormone levels. Epidemiological studies investigating breast cancer occurrence in insulin-treated patients with diabetes have produced conflicting results, but were often underpowered and lacked adequate control for important confounders.

Purpose: To investigate the impact of insulin treatment on mammographic density (MD) as intermediate phenotype for breast cancer risk, and to further explore causation by analyzing associations with a polygenic risk score (PRS) incorporating 18 single nucleotide polymorphisms (SNPs) associated with fasting insulin levels.

Design: We conducted a matched cohort study within a Swedish screening-based cohort including insulin-treated type 1 (T1D, N=122) and type 2 (T2D, N=237) diabetes patients and up to 5 non-diabetic women matched on birth year (N=1,780). Associations between diabetes status and duration of insulin use with volumetric mammographic density were analyzed using general linear models adjusting for a comprehensive set of potential confounders. PRS analyses were performed in an independent sample of non-diabetic women (N=9,437) from the same cohort.

Results: In multivariable analyses, T1D patients had higher percent (11.2 vs. 8.8%; P<0.001) and absolute dense volumes (66.6 vs. 60.8 cm3; P=0.09) and a lower absolute non-dense volume (513.2 vs. 617.7 cm3; P<0.001) compared to age-matched non-diabetics. Percent- and absolute dense volumes increased with increasing T1D duration, while no such trend was observed for the absolute non-dense volume. Similar associations but of smaller magnitude, were found in insulin-treated T2D patients. Genetically predicted higher fasting insulin levels among non-diabetes women were associated with increased percent and absolute dense volumes (% change per sd increase in PRS = 0.8 (0.0-1.6) and 0.9 (0.1-1.8) respectively), but no difference in absolute non-dense volume.

Conclusions: Our results demonstrate higher mammographic density among insulin-treated diabetes patients, and genetic analyses support an effect of insulin on volumetric mammographic density. Further studies into how the observed MD differences translate into breast cancer risk are warranted.

Citation Format: Borgquist S, Rosendahl AH, Czene K, Bhoo-Pathy N, Dorkhan M, Hall P, Brand JS. Insulin and breast cancer risk: Novel insights from mammographic density analyses [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 P2-07-03.

Muscle composition is regulated by a Lox-TGFβ feedback loop

Muscle is an integrated tissue composed of distinct cell types and extracellular matrix. While much emphasis has been placed on the factors required for the specification of the cells that comprise muscle, little is known about the crosstalk between them that enables the development of a patterned and functional tissue. We find in mice that deletion of lysyl oxidase (Lox), an extracellular enzyme regulating collagen maturation and organization, uncouples the balance between the amount of myofibers and that of muscle connective tissue (MCT). We show that Lox secreted from the myofibers attenuates TGFβ signaling, an inhibitor of myofiber differentiation and promoter of MCT development. We further demonstrate that a TGFβ-Lox feedback loop between the MCT and myofibers maintains the dynamic developmental homeostasis between muscle components while also regulating MCT organization. Our results allow a better understanding of diseases such as Duchenne muscular dystrophy, in which LOX and TGFβ signaling have been implicated and the balance between muscle constituents is disturbed.

Abstract P6-06-52: Increased expression of insulin-like growth factor-1 receptor is associated with better prognosis in a cohort of tamoxifen treated women

Background: Treatment resistance is a well-known problem in estrogen receptor (ER) positive breast cancer. Complementary therapies are investigated for women who do not respond or who develop resistance against standard ER targeted treatment. Insulin-like growth factor-1 receptor (IGF1R) and its signaling pathway has been suggested to cause estrogen-independent cell growth and survival. Therapy against targets within the pathway is currently investigated in clinical trials. The aim of this study was to investigate if the IGF1R/mTOR pathway was activated or deregulated in breast cancer patients and to explore if any of the markers were prognostic, with or without adjuvant tamoxifen.

Material and methods: Two patient cohorts were investigated by immunohistochemistry using tissue microarrays. The first cohort (N = 264) consisted of mainly post-menopausal women with stage II breast cancer treated with tamoxifen for 2 years irrespective of ER status. The second cohort (N = 206) consisted of mainly medically untreated, pre-menopausal patients with node-negative breast cancer. The protein expression of IGF1R, p-mTOR and p-S6rp were investigated. Cytoplasmic staining was evaluated for all markers and membrane staining was additionally evaluated for IGF1R. Statistical analyses were based on the intensity (0-3) of staining. Expression of IGF1R gave similar results in the cytoplasm and membrane, and p-values for cytoplasmic staining are reported below. Distant disease free survival (DDFS) at 5 years was used as end-point.

Results: IGF1R expression was positively associated with ERa (p<0.001 in Mann-Whitney ranksum test), PgR (p<0.001) and HER2 (p = 0.042) expression in cohort 1, and also with Ki67 (p = 0.006) in cohort 2. p-S6rp was positively associated with ERα in cohort 1 (p<0.001) and HER2 (p = 0.004) in cohort 2. p-mTOR was positively associated only with Ki67 (p<0.001) in cohort 1. High expression of IGF1R was associated with a significantly better prognosis in cohort 1 (HR = 0.7 per intensity step, 95% CI = 0.5-0.9, p = 0.016 using Cox regression). When stratifying for ER status the effect was found in ER negative (ER-) (N = 80, HR = 0.6, 95% CI = 0.4-1.0, p = 0.03) but not in ER positive (ER+) patients (N = 174, HR 1.2, 95% CI = 0.8-2.0, p = 0.40). Both the effect in the ER- subgroup as well as the difference between ER- and ER+ patients were confirmed in interaction analysis and remains after adjustment for age, tumor size, node status, HER2, Ki67, and menopausal status (p = 0.06 for interaction). In cohort 2, no relation to DDFS could be found for IGF1R. p-mTOR and p-S6rp showed no relationship to prognosis in either of the cohorts.

Conclusion: We found that high IGF1R expression was associated with a better prognosis for tamoxifen treated women. This effect could be seen in the ER- but not in the ER+ subgroup of patients. The lack of co-activation of downstream markers (p-mTOR and p-S6rp) in the IGF1R pathway shows that the prognostic effect is not due to complete activation of this pathway.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P6-06-52.

Polysaccharide-K (PSK) in cancer--old story, new possibilities?

Polysaccharide-K (PSK, Krestin) is one of the most commonly used medicinal mushroom extracts with a long history as an additive in cancer therapy in Asia, especially in Japan. PSK has a documented anti-tumor activity both in vitro and in vitro, in various types of cancers, including colorectal, gastric, breast, liver, pancreatic, and lung cancer. Despite PSK having been studied for about 40 years as an immune modulator and biological response modifier, the mechanisms of action by PSK have not yet been clearly and completely elucidated. This review aims to provide an up-to-date account for the effects of PSK in cancer with the hope of thereby providing an increased understanding of the molecular mechanisms of PSK and also its potential as an additive in modern cancer therapy.

IGF-II and IGFBP-2 differentially regulate PTEN in human breast cancer cells

The dual-function phosphatase and tensin homolog deleted on chromosome 10 (PTEN) is the second most frequently mutated gene in human cancers. PTEN counteracts the functions of many growth factors, the most prevalent of which is insulin-like growth factor II (IGF-II). PTEN expression is stimulated by IGF-II forming a feedback loop. Investigating IGF-binding protein (IGFBP) modulation of IGF-II actions on MCF-7 breast cancer cells, we found that IGFBP-2 also regulates PTEN. The MCF-7 cells were not responsive to high doses of IGF-II due to induction of PTEN, which was not observed with an IGF-II-analog that does not bind to IGFBPs or in the presence of an inhibitor that prevents IGFs associating with IGFBPs. These cells predominantly produce IGFBP-2: blocking IGFBP-2 with a specific antibody, or preventing IGFBP-2 binding to integrins, restored the induction of PTEN and the cells were non-responsive to high doses of the IGF-II-analog. Our findings indicate that breast cancer cells do not respond to high doses of IGF-II due to induction of PTEN, but IGFBP-2, when free from IGF-II can suppress PTEN. Levels of IGFBP-2 are elevated frequently in human tumors: its ability to regulate PTEN could have important implications in relation to therapeutic strategies targeting growth factor pathways.

IGF-I and IGFBP-3 augment transforming growth factor-beta actions in human renal carcinoma cells

Renal cell carcinoma (RCC) is the most prevalent cancer of the kidney. In human RCC cells, we recently showed that insulin-like growth factor I (IGF-I) has growth-promoting effects regulated by IGF-binding protein 3 (IGFBP-3). In this study, the analysis was expanded to include the interaction between the IGF and transforming growth factor-beta (TGF-beta) systems in the human RCC cells Caki-2 (from a primary tumor) and SK-RC-52 (from a metastasis). Functional effects such as cell proliferation, TGF-beta receptor (TbetaR) signaling, and IGFBP-3 levels were monitored after stimulation with various concentrations of IGF-I, TGF-beta, and IGFBP-3. In addition, human RCC tissues as well as experimental human RCC tumors were analyzed for cellular expression of phosphorylated Smad2 by immunohistochemistry. TGF-beta regulated the endogenous IGFBP-3 levels in these RCC cells as neutralizing anti-TGF-beta(1-3) antibodies strongly reduced the basal IGFBP-3 level. In addition, IGF-I increased the IGFBP-3 levels five- to eightfold with TGF-beta acting in synergy to enhance the IGFBP-3 levels 12- to 17-fold. Neutralizing TGF-beta(1-3) activity circumvented the growth inhibitory effects of IGFBP-3 seen in SK-RC-52, whereas it inhibited the growth-promoting effects of IGFBP-3 in Caki-2. Moreover, IGF-I interacted directly with TGF-beta activation of the TbetaR complex by enhancing phosphorylation and nuclear translocation of Smad2. This study demonstrates a direct interaction of the IGF and TGF-beta systems in human renal carcinoma cells. The observations that IGF-I enhances the TGF-beta signaling and that TGF-beta promotes IGFBP-3 production and thus influence the biological activity of IGF may be of importance for future therapeutic options.