Abstract 4818: Tolfenamic acid and curcumin treatment induces pancreatic cancer cell growth inhibition via suppressing Sp1 expression, NF-kB translocation to nucleus

Pancreatic cancer (PC) is an aggressive malignancy. The current treatment options have limited response in addressing poor prognosis and low survival rate. Hence it is important to identify novel agents and strategies for effective treatment. Previously the combination of phytochemical, curcumin (Cur) and cyclooxygenase (COX) inhibitor celecoxib was tested for improving therapeutic efficacy in PC models. The objective of current study is to identify a combination treatment involving a low toxic small molecule and a phytochemical with anti-cancer properties to inhibit PC cell growth. Experiments were also conducted to understand potential mechanisms associated with this combination. We tested the combination of an anti-cancer non-steroidal anti-inflammatory drug (NSAID), Tolfenamic Acid (TA) and Cur using PC cell lines, L3.6 and MIA PaCa-2. Cells were treated with 5-25 μM of Cur or 25-100 μM of TA or combination of Cur (7.5 μM) and TA (50 μM). Effect on cell viability was measured at 24, 48 and 72 h post-treatment using CellTiter-Glo kit. While the two agents showed anti-proliferative effect, Cur and TA combination caused higher growth inhibition. The cell growth inhibition was compared with two COX inhibitors, ibuprofen and celecoxib and the cardiotoxicity was assessed using cordiomyocytes (H9C2). TA showed significantly less cytotoxicity in cardiomyocytes when compared to celecoxib. The expression of transcription factors, Specificity protein1 (Sp1) and NF-kB, and an inhibitor of apoptosis family protein, survivin, were determined by Western blot analysis. The expression of NF-kB, Sp1 and survivin was decreased by combination treatment. The levels of reactive oxygen species (ROS) were also measured in flowcytometer. To evaluate the effect of these agents on apoptosis, the activity of caspase 3/7 was measured with caspase-Glo kit; apoptotic cell population was evaluated by Annexin-V staining (flow cytometry); and c-PARP expression was determined by Western blot analysis. When compared to individual agents, the combination treatment caused a significant increase in ROS levels and apoptotic markers. L3.6 and MIA PaCa-2 cells were treated with TNF-á to induce NF-kB translocation from cytoplasm to nucleus and the effect of individual (TA or Cur) and combined treatment (TA+Cur) on NF-kB translocation from cytoplasm to nucleus was evaluated by immunofluorescence. When compared to individual agents, the combination treatment caused a significant decrease in NF-kB translocation to nucleus. Cell cycle phase distribution was measured using flow cytometry. The combination treatment showed mostly DNA synthesis phase arrest; however TA caused cell cycle arrest in early phase (G0/G1). These results demonstrate that combination of Cur and TA effectively inhibits PC cell growth via inducing apoptosis and modulating cell cycle phase distribution.

Citation Format: Riyaz M. Basha, Sarah F. Connelly, Ganji Purnachandra, Umesh T. Sankpal, Hassaan Patel, Jamboor K. Vishwanatha, Sagar Shelake, Leslie Tabor-Simecka1, Mamoru Shoji, Jerry Simecka W. Simecka, Bassel El-Rayes. Tolfenamic acid and curcumin treatment induces pancreatic cancer cell growth inhibition via suppressing Sp1 expression, NF-kB translocation to nucleus. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4818.

Small molecule tolfenamic acid and dietary spice curcumin treatment enhances antiproliferative effect in pancreatic cancer cells via suppressing Sp1, disrupting NF-kB translocation to nucleus and cell cycle phase distribution

Combination of dietary/herbal spice curcumin (Cur) and COX inhibitors has been tested for improving therapeutic efficacy in pancreatic cancer (PC). The objective of this study was to identify agent with low toxicity and COX-independent mechanism to induce PC cell growth inhibition when used along with Cur. Anticancer NSAID, tolfenamic acid (TA) and Cur combination were evaluated using PC cell lines. L3.6pl and MIA PaCa-2 cells were treated with Cur (5-25μM) or TA (25-100μM) or combination of Cur (7.5μM) and TA (50μM). Cell viability was measured at 24-72h posttreatment using CellTiter-Glo kit. While both agents showed a steady/consistent effect, Cur+TA caused higher growth inhibition. Antiproliferative effect was compared with COX inhibitors, Ibuprofen and Celebrex. Cardiotoxicity was assessed using cordiomyocytes (H9C2). The expression of Sp proteins, survivin and apoptotic markers (western blot), caspase 3/7 (caspase-Glo kit), Annexin-V staining (flow cytometry), reactive oxygen species (ROS) and cell cycle phase distribution (flow cytometry) was measured. Cells were treated with TNF-α, and NF-kB translocation from cytoplasm to nucleus was evaluated (immunofluorescence). When compared to individual agents, combination of Cur+TA caused significant increase in apoptotic markers, ROS levels and inhibited NF-kB translocation to nucleus. TA caused cell cycle arrest in G0/G1, and the combination treatment showed mostly DNA synthesis phase arrest. These results suggest that combination of Cur+TA is less toxic and effectively enhance the therapeutic efficacy in PC cells via COX-independent mechanisms.

Abstract 4216: Combination of anti-cancer small molecule tolfenamic acid and curcumin or curcumin analog EF31 effectively inhibits pancreatic cancer cell growth

Tolfenamic acid (TA), a non-steroidal anti-inflammatory drug is known to inhibit human cancer cells and mouse tumor growth in some cancer models. TA is known to target the transcription factor, specificity protein1 (Sp1) that mediates the expression of several genes associated with cancer including survivin, a key member of inhibitor of apoptosis proteins (IAP) family. It is currently in phase I clinical trials for treating upper gastro-intestinal cancer patients along with radiation. Curcumin (Cur) is an aromatic constituent of the plant curcuma longa (turmeric) which is extensively studied in some malignancies including breast, pancreatic and colon cancers. Even though, Cur shows a broad spectrum of anti-cancer activity in pre-clinical studies, its clinical application is greatly affected by its low bioavailability. Hence the strategies to improve the response to Cur soared by synthesizing and testing analogs. Recently our group showed that EF31 impacts the DNA methylation and causes anti-proliferative effect in pancreatic cancer cell liens and inhibits tumor growth in mice xenografts. We have evaluated the therapeutic efficacy of Cur and a Cur analog EF31 in combination with an anti-cancer small molecule, TA using human pancreatic cancer cell lines, MiaPaCa2 and L3.6 pl. MiaPaCa2 and L3.6 pl cells were treated with increasing concentrations of TA (25-100 µM) or Cur (5-25 µM) or EF31 (0.2-5 µM) or combination of optimized concentrations of TA (50 µM) and Cur (7.5 µM) or EF31 (0.5 µM) and the cell viability was measured at 24, 48, and 72 h post-treatment. All agents showed a steady and consistent decrease in cell viability following a clear dose and time-dependent response while the combination of TA and Cur or EF31 showed higher growth inhibition. Apoptosis and cell cycle analysis was performed using flow cytometry. Results showed a significant increase in the apoptotic fraction (annexin V positive) following combination treatment when compared to individual effect. TA caused cell cycle arrest in G0/G1 and the combination treatment showed both G0/G1 and G2 arrest. The activation of apoptosis was further confirmed by examining the activation of caspases (caspase 3/7, 8 and 9) and the expression of cleaved PARP. The Western blot results revealed that TA significantly decreased Sp1 and survivin expression and the combination of TA and Cur or TA and EF31 significantly modulated the expression of critical candidates associated with cell cycle. When compared to Cur, its synthetic analog EF31 showed higher efficacy in both individual and combination studies. These pre-clinical results demonstrate that the combination of anti-cancer NSAID, tolfenamic acid and curcumin or curcumin analogs may enhance the therapeutic efficacy in pancreatic cancer. Studies to better understand the underlying mechanisms by performing molecular profiling are currently under investigation.

Citation Format: Riyaz Basha, Sarah F. Connelly, Ganji Purnachandra Nagaraju, Umesh T. Sankpal, Mamoru Shoji, Omar Kayaleh, Bassel El-Rayes. Combination of anti-cancer small molecule tolfenamic acid and curcumin or curcumin analog EF31 effectively inhibits pancreatic cancer cell growth. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4216. doi:10.1158/1538-7445.AM2014-4216

Anti-leukemic response of a NSAID, tolfenamic acid

Tolfenamic acid (TA), a non-steroidal anti-inflammatory drug, is known to inhibit human cancer cells and mouse tumor growth in some cancer models; however, its anti-leukemic response has not been evaluated. TA targets specificity protein (Sp) transcription factors that mediate the expression of several genes associated with cancer including survivin, a key member of inhibitor of apoptosis protein family. Our aim was to test the anti-leukemic efficacy of TA in pre-clinical experiments. The anti-leukemic response of TA was determined using Jurkat and Nalm-6 cell lines. Cells were treated with increasing (25/50/75 μM) concentrations of TA, and cell viability was measured at 24, 48, and 72 h post-treatment. TA showed a steady and consistent decrease in cell viability following a clear dose and time dependent response. Apoptosis and cell cycle analysis was performed using flow cytometry. Results showed a significant increase in the apoptotic fraction (annexin V positive) following TA treatment, while cell cycle phase distribution analysis showed G0/G1 arrest. TA-induced apoptosis was further confirmed by examining the activation of caspase 3/7 and the expression of cleaved PARP. TA modulated the expression of critical candidates associated with the early phases of cell cycle and validated its efficacy in causing G0/G1 arrest. The Western blot results revealed that TA significantly decreases Sp1 and survivin expression. These results demonstrate that the anti-leukemic response of TA occurs potentially through targeting Sp1 and inhibiting survivin and suggest the efficacy of TA as a novel therapeutic agent for leukemia.

Abstract 2770: Anti-leukemic response of a NSAID, tolfenamic acid

Tolfenamic acid (TA), a non-steroidal anti-inflammatory drug is known to inhibit human cancer cells and mouse tumor growth in some cancer models; however its anti-leukemic response is not yet evaluated. Research from our laboratory and others showed that TA targets specificity protein (Sp) transcription factors which mediate the expression of several genes associated with cancer. We also showed that TA inhibits the expression of survivin, a key member of inhibitor of apoptosis family in several human cancer cells. Recent work from several laboratories revealed a strong association of survivin in leukemia. We hypothesize by targeting Sp proteins and survivin, TA can act as an anti-leukemic agent. The anti-proliferative response of TA was determined using four human leukemia cell lines, Jurkat (acute T-cell leukemia), Nalm-6 (pre-B cell leukemia), Molt-4 (acute lymphoblastic leukemia; T lymphoblast), and Reh (acute lymphoblastic leukemia, non-T; non-B) Cells were treated with increasing (25/50/75/100 μM) concentrations of TA and the cell viability was measured at 24, 48, and 72 h post-treatment using CellTiter-Glo kit. Results show a consistent decrease in cell viability in a dose and time-dependent manner. Confirmatory studies to elucidate the mechanism of action were conducted using selected cell lines, Jurkat and Nalm-6. Apoptosis and cell cycle analysis was performed using flow cytometry. The expression of c-PARP, Sp1, survivin, CDC2, CDC4, Cyclin D3 and pRb was determined by Western blot analysis and the caspases were measured by using Caspse-Glo kit(s). Results showed a significant increase in the apoptotic (annexin V positive) cell population following TA treatment, while cell cycle phase distribution analysis showed G0/G1 arrest. TA-induced cell apoptosis is supported by robust activation of caspases (3/7, 8 and 9), and the expression of c-PARP. TA down-regulated the expression of CDC2, CDC4, Cyclin D3 and pRb that mediate the early phases of cell cycle. In summary, TA modulated the expression of critical candidate genes associated with the early phases of cell cycle with validated efficacy in causing G0/G1 arrest. Western blot results reveal that TA significantly decreases Sp1 and survivin expression. Further work is needed to clarify the role of TA as a novel therapeutic agent for leukemia.

Citation Format: Robert M. Sutphin, Sarah F. Connelly, Chris M. Lee, Umesh T. Sankpal, Don Eslin, Riyaz Basha. Anti-leukemic response of a NSAID, tolfenamic acid. [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 2770. doi:10.1158/1538-7445.AM2013-2770

Small molecule tolfenamic acid inhibits PC-3 cell proliferation and invasion in vitro, and tumor growth in orthotopic mouse model for prostate cancer

BACKGROUND

Specificity protein (Sp) transcription factors are implicated in critical cellular and molecular processes associated with cancer that impact tumor growth and metastasis. The non-steroidal anti-inflammatory drug, tolfenamic acid (TA) is known to inhibit Sp proteins in some human cancer cells and laboratory animal models. We evaluated the anti-cancer activity of TA using in vitro and in vivo models for prostate cancer.

METHODS

The anti-proliferative efficacy of TA was evaluated using DU-145, PC-3, and LNCaP cells. PC-3 cells were treated with DMSO or 50 µM TA for 48 hr. Whole cell lysates were evaluated for the expression of Sp1, survivin, c-PARP, Akt/p-Akt, c-Met, cdk4, cdc2, cyclin D3, and E2F1 by Western blot analysis. Cell invasion was assessed by Boyden-chamber assay and flow cytometry analysis was used to study apoptosis and cell cycle distribution. An orthotopic mouse model for prostate cancer with PC-3-Luc cells was used to study the in vivo effect of TA.

RESULTS

TA inhibited the expression of Sp1, c-Met, p-Akt, and survivin; increased c-PARP expression and caspases activity in PC-3 cells. TA caused cell arrest at G(0) /G(1) phase accompanied by a decrease in cdk4, cdc2, cyclin D3, and E2F1 and an increase in critical apoptotic markers. TA augmented annexin-V staining, caspase activity, and c-PARP expression indicating the activation of apoptotic pathways. TA also decreased PC-3 cell invasion. TA significantly decreased the tumor weight and volume which was associated with low expression of Sp1 and survivin in tumor sections.

CONCLUSION

TA targets critical pathways associated with tumorigenesis and invasion. These pre-clinical data strongly demonstrated the anti-cancer activity of TA in prostate cancer.

Tolfenamic acid suppresses cytochrome P450 2E1 expression in mouse liver

Non-steroidal anti-inflammatory drugs (NSAIDs) play a significant role in the chemoprevention of cancer. We recently showed the chemopreventive response of a NSAID, 2-[(3-chloro-2-methylphenyl)amino]benzoic acid) known as tolfenamic acid (TA) in N-nitrosomethylbenzylamine (NMBA)-induced esophageal tumors in rats. Pre-clinical studies showed that TA inhibits Specificity protein (Sp) transcription factors and acts as an anti-cancer agent in several cancer models; however the pertinent mechanisms associated with its chemopreventive response in esophageal cancer are not known. Since the bioactivation of carcinogens through cytochrome P450 (CYP) is critical for the induction of cancer, we have studied the effect of TA on critical CYP isozymes in mouse liver samples. Athymic nude mice were treated with vehicle (corn oil) or TA (50 mg kg(-1), 3 times per week) for 4 weeks. Protein extracts (whole cell lysates and microsomal fractions) were prepared from liver tissue and the expression of various CYP isozymes was determined by Western blot analysis. Rat (Sprague-Dawley) livers were harvested and primary hepatocyte cultures were treated with vehicle (DMSO) or TA (50 μM) and cell viability was assessed at 2 and 5 days post-treatment. TA caused remarkable decrease in the expression of CYP2E1 in both liver lysates and sub-cellular fraction, while its response on other tested isozymes was marginal. TA did not affect the body weight of animals (mice) and viability of rat hepatocytes. These results demonstrate that TA modulates the expression of CYP2E1 which is associated with the bioactivation of carcinogens without causing apparent toxicity. These data suggest that TA-induced inhibition of CYP2E1 attenuates the bioactivation of carcinogens potentially leading to the chemoprevention of NMBA-induced esophageal tumorigenesis in rats.

Environmental factors in causing human cancers: emphasis on tumorigenesis

The environment and dietary factors play an essential role in the etiology of cancer. Environmental component is implicated in ~80 % of all cancers; however, the causes for certain cancers are still unknown. The potential players associated with various cancers include chemicals, heavy metals, diet, radiation, and smoking. Lifestyle habits such as smoking and alcohol consumption, exposure to certain chemicals (e.g., polycyclic aromatic hydrocarbons, organochlorines), metals and pesticides also pose risk in causing human cancers. Several studies indicated a strong association of lung cancer with the exposure to tobacco products and asbestos. The contribution of excessive sunlight, radiation, occupational exposure (e.g., painting, coal, and certain metals) is also well established in cancer. Smoking, excessive alcohol intake, consumption of an unhealthy diet, and lack of physical activity can act as risk factors for cancer and also impact the prognosis. Even though the environmental disposition is linked to cancer, the level and duration of carcinogen-exposure and associated cellular and biochemical aspects determine the actual risk. Modulations in metabolism and DNA adduct formation are considered central mechanisms in environmental carcinogenesis. This review describes the major environmental contributors in causing cancer with an emphasis on molecular aspects associated with environmental disposition in carcinogenesis.

Abstract 2859: Dual targeting of protein tyrosine kinase c-Src and protein tyrosine phosphatase SHP-2 is a novel therapeutic strategy that induces potent inhibition of pancreatic cancer cell viability in vitro and tumor progression in vivo

Pancreatic adenocarcinoma is a deadly human malignancy, with over 95% of patients succumbing within five years. The majority of pancreatic cancer deaths are caused by metastatic dissemination of the primary tumor. The only curative treatment is surgical resection, which is limited by tumor stage, and the standard chemotherapeutic option, gemcitabine, offers only modest survival and quality of life benefits. There is a need for a greater understanding of pancreatic cancer biology and development of novel therapies to inhibit tumor progression and metastasis. The non-receptor protein tyrosine kinase, c-Src (Src) has emerged as a potential target for the treatment of pancreatic cancer, having been demonstrated to promote a number of tumorigenic processes. Src is overexpressed and/or aberrantly activated in greater than 70% of human pancreatic cancers. In addition, SHP-2, a non-receptor protein tyrosine phosphatase, regulates Src family kinase activity. Evidence has established clinical relevance for SHP-2 in human diseases. A recent study demonstrated that inhibition of SHP-2 abrogates in vitro and in vivo angiogenesis and inhibits activity of the MAPK/Erk1/2 and PI3K/Akt survival pathways. SHP-2 and Src function as key signaling intermediates downstream of growth factor receptors, cytokine receptors, and integrins, and are crucial for activation of downstream cascades of tumor progression and metastasis. The purpose of this study was to determine the importance of SHP-2 and Src, for pancreatic cancer signaling, cell biology, tumorigenicity, and metastasis. We have demonstrated elevated SHP-2 expression and phosphorylation in pancreatic cancer cells, relative to normal pancreatic cells. Phosphorylation of SHP-2 in pancreatic cancer cells occurs in a Src kinase-dependent fashion. Functional inhibition of SHP-2 and Src, individually or in combination, resulted in reduced ERK-1/2 phosphorylation, increased cleavage of caspase 3 and PARP, increased expression of the pro-apoptotic protein Bax, and decreased levels of the anti-apoptotic protein Bcl-xL. These results were mirrored by decreased viability and increased caspase activity in the presence of Src and SHP-2 inhibition. Finally, treatment of mice with small molecule inhibitors of Src or SHP-2, produced markedly smaller pancreatic tumors relative to controls in an orthotopic nude mouse model and dual treatment exacerbated this effect. The potential use for the Src and SHP-2 signaling axes as therapeutic targets remains largely untapped. These data suggest the importance of SHP-2 in pancreatic cancer cell biology and its potential value as a therapeutic target. Our studies suggest that the anti-tumor/anti-metastatic effects of Src inhibition may be improved through simultaneous inhibition of SHP-2.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2859. doi:1538-7445.AM2012-2859

Abstract 1237: Role of Src in resistance to anoikis in detachedpancreatic cancer cells

Pancreatic adenocarcinoma is an aggressive malignancy currently ranked as the fourth leading cause of cancer related death in the United States, with over 95% of patients succumbing to the disease within 5 years of diagnosis. The vast majority of pancreatic cancer deaths are due to metastatic dissemination of the primary tumor. The non-receptor protein tyrosine kinase, c-Src (Src) has emerged in recent years as a potential target for pancreatic cancer treatment. In vitro studies have demonstrated the importance of Src for pancreatic tumor cell adhesion, migration, invasiveness, and resistance to apoptotic death. Mouse models of pancreatic cancer have indicated an important role for Src in formation of metastases. In addition, SHP-2, a non-receptor protein tyrosine phosphatase that regulates Src family kinase activity, has been recently shown to be a key mediator of various signaling pathways and evidence has established clinical relevance for SHP-2 in human diseases. Our goal is to determine the importance of Src for discrete steps in the progression to pancreatic cancer metastasis and resistance to detachment-induced cell death and the role of SHP-2 in modulating Src activity and downstream biology during this process. We have demonstrated a rapid and robust activation of Src in L3.6 human pancreatic cancer cells that have become detached from the extracellular environment, a crucial step in the development of metastases. Also, we have observed co-immunoprecipitation between Src and SHP-2 in detached cells, suggesting a potential role for SHP-2 in regulating Src activity in detached pancreatic cancer cells. In addition, our results reveal a Src-dependent activation of the Akt cell survival cascade and the stress kinase, Jun N-terminal kinase (JNK) in detached cells. Furthermore, this study confirmed that inhibition of both Src and SHP-2 in combination sensitizes L3.6 pancreatic cancer cells to anoikis in detached cells. We hypothesize that Src activity in detached pancreatic cancer cells promotes metastasis through suppression of anoikis. We will confirm these in vitro studies by testing the effects of inhibition of Src alone or in combination with SHP-2 inhibition on metastatic tumor formation using a nude mouse experimental metastasis model. The potential use for the Src and SHP-2 signaling axes as therapeutic targets for many cancers remains largely untapped. Our studies suggest that the anti-tumor and anti-metastatic effects of Src inhibition may be improved through simultaneous inhibition of SHP-2.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1237. doi:10.1158/1538-7445.AM2011-1237

Loss of tyrosine phosphatase-dependent inhibition promotes activation of tyrosine kinase c-Src in detached pancreatic cells

Despite an intense focus on novel therapeutic strategies, pancreatic adenocarcinoma remains one of the deadliest human malignancies. The frequent and rapid mortality associated with pancreatic cancer may be attributed to several factors, including late diagnosis, rapid tumor invasion into surrounding tissues, and formation of distant metastases. Both local invasion and metastasis require disruption of tumor cell contacts with the extracellular matrix. Detachment of normal cells from the extracellular matrix leads to a form of programmed cell death termed anoikis. Pancreatic cancer cells avert anoikis by activation of signaling pathways that allow for adhesion-independent survival. In the present studies, cellular signaling pathways activated in detached pancreatic cancer cells were examined. We demonstrate a rapid and robust activation of Src kinase in detached pancreatic cancer cells, relative to adherent. Src autophosphorylation rapidly returned to baseline levels upon reattachment to tissue culture plastic, in the presence or absence of specific extracellular matrix proteins. Treatment of pancreatic cancer cells with tyrosine phosphatase inhibitors increased steady-state Src autophosphorylation in adherent cells and abrogated the detachment-induced increase in Src autophosphorylation. Src was found to co-immunoprecipitate with the Src homology 2 (SH2) domain containing protein tyrosine phosphatase (SHP-2) in pancreatic cancer cells, suggesting that SHP-2 may participate in regulation of Src autophosphorylation in adherent cells. Src family kinase (SFK) dependent increases in Akt and Jun N-terminal kinase (JNK) phosphorylation were observed in detached cells, indicating the potential for Src-dependent activation of survival and stress pathways in pancreatic cancer cells that have detached from the extracellular matrix.