Altered expression and activation of the nerve growth factor receptors TrkA and p75 provide the first evidence of tumor progression to effusion in breast carcinoma

Regulating tumor innervation by nanodrugs potentiates cancer immunochemotherapy and relieve chemotherapy-induced neuropathic pain

Sympathetic nerves play a pivotal role in promoting tumor growth through crosstalk with tumor and stromal cells. Chemotherapy exacerbates the infiltration of sympathetic nerves into tumors, thereby providing a rationale for inhibiting sympathetic innervation to enhance chemotherapy. Here, we discovered that doxorubicin increases the density and activity of sympathetic nerves in breast cancer mainly by upregulating the expression of nerve growth factors (NGFs) in cancer cells. To address this, we developed a combination therapy by co-encapsulating small interfering RNA (siRNA) and doxorubicin within breast cancer-targeted poly (lactic-co-glycolic acid) (PLGA) nanoparticles, aiming to suppress NGF expression post-chemotherapy. Incorporating NGF blockade into the nanoplatform for chemotherapy effectively mitigated the chemotherapy-induced proliferation of sympathetic nerves. This not only bolstered the tumoricidal activity of chemotherapy, but also amplified its stimulatory impact on the antitumor immune response by increasing the infiltration of immunostimulatory cells into tumors while concurrently reducing the frequency of immunosuppressive cells. Consequently, the combined nanodrug approach, when coupled with anti-PD-L1 treatment, exhibited a remarkable suppression of primary and deeply metastatic tumors with minimal systematic toxicity. Importantly, the nanoplatform relieved chemotherapy-induced peripheral neuropathic pain (CIPNP) by diminishing the expression of pain mediator NGFs. In summary, this research underscores the significant potential of NGF knockdown in enhancing immunochemotherapy outcomes and presents a nanoplatform for the highly efficient and low-toxicity treatment of breast cancer.

Expression and Signaling Pathways of Nerve Growth Factor (NGF) and Pro-NGF in Breast Cancer: A Systematic Review

Breast cancer represents the most common type of cancer and is the leading cause of death due to cancer among women. Thus, the prevention and early diagnosis of breast cancer is of primary urgency, as well as the development of new treatments able to improve its prognosis. Nerve Growth Factor (NGF) is a neurotrophic factor involved in the regulation of neuronal functions through the binding of the Tropomyosin receptor kinase A (TrkA) and the Nerve Growth Factor receptor or Pan-Neurotrophin Receptor 75 (NGFR/p75NTR). In addition, its precursor (pro-NGF) can extert biological activity by forming a trimeric complex with NGFR/p75NTR and sortilin, or by binding to TrkA receptors with low affinity. Several examples of in vitro and in vivo evidence show that NGF is both synthesized and released by breast cancer cells, and has mitogen, antiapoptotic and angiogenic effects on these cells through the activation of different signaling cascades that involve TrkA and NGFR/p75NTR receptors. Conversely, pro-NGF signaling has been related to breast cancer invasion and metastasis. Other studies suggested that NGF and its receptors could represent a good diagnostic and prognostic tool, as well as promising therapeutic targets for breast cancer. In this paper, we comprehensively summarize and systematically review the current experimental evidence on this topic. INPLASY ID: INPLASY2022100017.

NGF/TRKA Promotes ADAM17-Dependent Cleavage of P75 in Ovarian Cells: Elucidating a Pro-Tumoral Mechanism

Nerve growth factor (NGF) and its high-affinity receptor TRKA are overexpressed in epithelial ovarian cancer (EOC) displaying a crucial role in the disease progression. Otherwise, NGF interacts with its low-affinity receptor P75, activating pro-apoptotic pathways. In neurons, P75 could be cleaved by metalloproteinases (α and γ-secretases), leading to a decrease in P75 signaling. Therefore, this study aimed to evaluate whether the shedding of P75 occurs in EOC cells and whether NGF/TRKA could promote the cleavage of the P75 receptor. The immunodetection of the α-secretase, ADAM17, TRKA, P75, and P75 fragments was assessed by immunohisto/cytochemistry and Western blot in biopsies and ovarian cell lines. The TRKA and secretases' inhibition was performed using specific inhibitors. The results show that P75 immunodetection decreased during EOC progression and was negatively correlated with the presence of TRKA in EOC biopsies. NGF/TRKA increases ADAM17 levels and the fragments of P75 in ovarian cells. This effect is abolished when cells are previously treated with ADAM17, γ-secretase, and TRKA inhibitors. These results indicate that NGF/TRKA promotes the shedding of P75, involving the activation of secretases such as ADAM17. Since ADAM17 has been proposed as a screening marker for early detection of EOC, our results contribute to understanding better the role of ADAM17 and NGF/TRKA in EOC pathogenesis, which includes the NGF/TRKA-mediated cleavage of P75.

The Receptor Tyrosine Kinase TrkA Is Increased and Targetable in HER2-Positive Breast Cancer

The tyrosine kinase receptor A (NTRK1/TrkA) is increasingly regarded as a therapeutic target in oncology. In breast cancer, TrkA contributes to metastasis but the clinicopathological significance remains unclear. In this study, TrkA expression was assessed via immunohistochemistry of 158 invasive ductal carcinomas (IDC), 158 invasive lobular carcinomas (ILC) and 50 ductal carcinomas in situ (DCIS). TrkA was expressed in cancer epithelial and myoepithelial cells, with higher levels of TrkA positively associated with IDC (39% of cases) (p < 0.0001). Interestingly, TrkA was significantly increased in tumours expressing the human epidermal growth factor receptor-2 (HER2), with expression in 49% of HER2-positive compared to 25% of HER2-negative tumours (p = 0.0027). A panel of breast cancer cells were used to confirm TrkA protein expression, demonstrating higher levels of TrkA (total and phosphorylated) in HER2-positive cell lines. Functional investigations using four different HER2-positive breast cancer cell lines indicated that the Trk tyrosine kinase inhibitor GNF-5837 reduced cell viability, through decreased phospho-TrkA (Tyr490) and downstream AKT (Ser473) activation, but did not display synergy with Herceptin. Overall, these data highlight a relationship between the tyrosine kinase receptors TrkA and HER2 and suggest the potential of TrkA as a novel or adjunct target for HER2-positive breast tumours.

Greater specificity of p40 compared with p63 in distinguishing squamous cell carcinoma from adenocarcinoma in effusion cellblocks

Objective

Squamous cell carcinoma (SCC) rarely causes malignant effusions. Distinguishing between SCC and adenocarcinoma in effusion cytology can be a challenge. p63 and p40 have been frequently used to support squamous cell differentiation in both histological and cytological specimens. However, similar results in cytological preparations of effusion fluids have been rarely reported. This study was designed to assess the diagnostic value of p63 and p40 immunoreactivity for the differentiation of SCC from adenocarcinoma in malignant effusions.

Materials and Methods

Immunocytochemical staining of p63 and p40 was performed on thirty cellblock specimens, including ten malignant effusions carrying SCC and twenty malignant effusions showing adenocarcinoma. Any degree of nuclear staining was considered positive.

Results

Of the ten SCC cases, 100% tested positive for both p63 and p40, and most cases showed diffuse staining (>25% of tumor cells). The expression of p63 and p40 was detected in 4 (20%) and 2 (10%) of twenty adenocarcinoma cases, and the extent of staining was all focal (≤25% of tumor cells). The p63 reactivity showed 100% sensitivity, 80% specificity, 71% positive predictive value, and 100% negative predictive value for the differentiation of SCC from adenocarcinoma in malignant effusions. The sensitivity of p40 for SCC was 100%, the specificity was 90%, the positive predictive value was 83%, and the negative predictive value was 100%.

Conclusion

Although p63 and p40 are both useful markers for the diagnosis of SCC in malignant effusions, p40 is more specific than p63 in distinguishing SCC from adenocarcinoma.

Expression and Prognostic Significance of Neurotrophins and Their Receptors in Canine Mammary Tumors

Accumulating data highlight the role of neurotrophins and their receptors in human breast cancer. This family includes nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF), both synthetized as proneurotrophins (proNGF and proBDNF). (pro)NGF and (pro)BDNF initiate their biological effects by binding to both their specific receptors TrkA and TrkB, respectively, and the common receptor p75^NTR. Currently, no data are available about their expression and potential role in canine mammary tumors. The aim of this study was to investigate expression of proNGF and BDNF as well as their receptors TrkA, TrkB, and p75^NTR in canine mammary carcinomas, and to correlate them with clinicopathological parameters (grade, histological type, lymph node status, recurrence, and distant metastasis) and survival. Immunohistochemistry was performed on serial sections of 96 canine mammary carcinomas with antibodies against proNGF, BDNF, TrkA, TrkB, and p75^NTR. Of the 96 carcinomas, proNGF expression was detected in 71 (74%), BDNF in 79 (82%), TrkA in 94 (98%), TrkB in 35 (37%), and p75^NTR in 44 (46%). No association was observed between proNGF, BDNF, or TrkA expression and either clinicopathological parameters or survival. TrkB and p75^NTR expression were associated with favorable clinicopathological parameters as well as better overall survival.

ProNGF increases breast tumor aggressiveness through functional association of TrkA with EphA2

ProNGF expression has been linked to several types of cancers including breast cancer, and we have previously shown that proNGF stimulates breast cancer invasion in an autocrine manner through membrane receptors sortilin and TrkA. However, little is known regarding TrkA-associated protein partners upon proNGF stimulation. By proteomic analysis and proximity ligation assays, we found that proNGF binding to sortilin induced sequential formation of the functional sortilin/TrkA/EphA2 complex, leading to TrkA-phosphorylation dependent Akt activation and EphA2-dependent Src activation. EphA2 inhibition using siRNA approach abolished proNGF-stimulated clonogenic growth of breast cancer cell lines. Combinatorial targeting of TrkA and EphA2 dramatically reduced colony formation in vitro, primary tumor growth and metastatic dissemination towards the brain in vivo. Finally, proximity ligation assay in breast tumor samples revealed that increased TrkA/EphA2 proximity ligation assay signals were correlated with a decrease of overall survival in patients. All together, these data point out the importance of TrkA/EphA2 functional association in proNGF-induced tumor promoting effects, and provide a rationale to target proNGF/TrkA/EphA2 axis by alternative methods other than the simple use of tyrosine kinase inhibitors in breast cancer.

Inhibiting TRK Proteins in Clinical Cancer Therapy

Gene rearrangements resulting in the aberrant activity of tyrosine kinases have been identified as drivers of oncogenesis in a variety of cancers. The tropomyosin receptor kinase (TRK) family of tyrosine receptor kinases is emerging as an important target for cancer therapeutics. The TRK family contains three members, TRKA, TRKB, and TRKC, and these proteins are encoded by the genes NTRK1, NTRK2, and NTRK3, respectively. To activate TRK receptors, neurotrophins bind to the extracellular region stimulating dimerization, phosphorylation, and activation of downstream signaling pathways. Major known downstream pathways include RAS/MAPK/ERK, PLCγ, and PI3K/Akt. While being rare in most cancers, TRK fusions with other proteins have been well-established as oncogenic events in specific malignancies, including glioblastoma, papillary thyroid carcinoma, and secretory breast carcinomas. TRK protein amplification as well as alternative splicing events have also been described as contributors to cancer pathogenesis. For patients harboring alterations in TRK expression or activity, TRK inhibition emerges as an important therapeutic target. To date, multiple trials testing TRK-inhibiting compounds in various cancers are underway. In this review, we will summarize the current therapeutic trials for neoplasms involving NTKR gene alterations, as well as the promises and setbacks that are associated with targeting gene fusions.

Gelatin-albumin hybrid nanoparticles as matrix metalloproteinases-degradable delivery systems for breast cancer therapy

AIM

To develop matrix metalloproteinase-responsive gelatin-albumin hybrid nanoparticles encapsulating a selective tropomyosin receptor kinase A (TrkA) inhibitor GNF-5837 (Gel-Alb-GNF HNPs) and to demonstrate their anticancer effects in breast cancer.

METHODS

Gel-Alb-GNF HNPs were prepared using a pH-controlled complexation process from cationic gelatin, dextran sulfate and albumin-bound GNF-5837. The anticancer activities of Gel-Alb-GNF HNPs were tested in a panel of subtype-specific breast cancer cell lines.

RESULTS

Gel-Alb-GNF HNPs (∼130 nm) displayed excellent stability and matrix metalloproteinase-triggered drug release. Compared with GNF-5837 alone, Gel-Alb-GNF HNPs not only significantly enhanced the antiproliferative and anti-invasive effects but also restored the apoptosis of cancer cells.

CONCLUSION

Gel-Alb-GNF HNPs may be adaptable for stand-alone therapies or used in combination with traditional chemotherapies for breast cancer treatment.

ProNGF, but Not NGF, Switches from Neurotrophic to Apoptotic Activity in Response to Reductions in TrkA Receptor Levels

Nerve growth factor (NGF) promotes the survival and differentiation of neurons. NGF is initially synthesized as a precursor, proNGF, which is the predominant form in the central nervous system. NGF and proNGF bind to TrkA/p75NTR to mediate cell survival and to sortilin/p75NTR to promote apoptosis. The ratio of TrkA to p75NTR affects whether proNGF and mature NGF signal cell survival or apoptosis. The purpose of this study was to determine whether the loss of TrkA influences p75NTR or sortilin expression levels, and to establish whether proNGF and mature NGF have a similar ability to switch between cell survival and cell death. We systematically altered TrkA receptor levels by priming cells with NGF, using small interfering RNA, and using the mutagenized PC12nnr5 cell line. We found that both NGF and proNGF can support cell survival in cells expressing TrkA, even in the presence of p75NTR and sortilin. However, when TrkA is reduced, proNGF signals cell death, while NGF exhibits no activity. In the absence of TrkA, proNGF-induced cell death occurs, even when p75NTR and sortilin levels are reduced. These results show that proNGF can switch between neurotrophic and apoptotic activity in response to changes in TrkA receptor levels, whereas mature NGF cannot. These results also support the model that proNGF is neurotrophic under normal circumstances, but that a loss in TrkA in the presence of p75NTR and sortilin, as occurs in neurodegenerative disease or injury, shifts proNGF, but not NGF, signalling from cell survival to cell death.

Localization of TrkB and p75 receptors in peritoneal and deep infiltrating endometriosis: an immunohistochemical study

BACKGROUND

The roles of the neurotrophins NGF (Neurotrophic growth factor) and BDNF (brain-derived neurotrophic factor) in neuronal growth and development are already known. Meanwhile, the neurotrophin receptors TrkA (tropomyosin related kinase A), TrkB, and p75 are important for determining the fate of cells. In endometriosis, this complex system has not been fully elucidated yet. The aim of this study was to evaluate the expression and location of these neurotrophins and their receptors in peritoneal (PE) and deep infiltrating endometriotic (DIE) tissues and to measure and compare the density of nerve fibers in the disease subtypes.

METHODS

PE lesions (n = 20) and DIE lesions (n = 22) were immunostained and analyzed on serial slides with anti-BDNF, -NGF, -TrkA, -TrkB, -p75,-protein gene product 9.5 (PGP9.5, intact nerve fibers) and -tyrosine hydroxylase (TH, sympathetic nerve fibers) antibodies.

RESULT

There was an equally high percentage (greater than 75 %) of BDNF-positive immunostaining cells in both PE and DIE. TrkB (major BDNF receptor) and p75 showed a higher percentage of immunostaining cells in DIE compared to in PE in stroma only (p < 0.014, p < 0.027, respectively). Both gland and stroma of DIE lesions had a lower percentage of NGF-positive immunostaining cells compared to those in PE lesions (p < 0.01 and p < 0.01, respectively), but there was no significant reduction in immunostaining of TrkA in DIE lesions. There was no difference in the mean density of nerve fibers stained with PGP9.5 between PE (26.27 ± 17.32) and DIE (28.19 ± 33.15, p = 0.8). When we performed sub-group analysis, the density of nerves was significantly higher in the bowel DIE (mean 57.33 ± 43.9) than in PE (mean 26.27 ± 17.32, p < 0.01) and non-bowel DIE (mean 14.6. ± 8.6 p < 0.002).

CONCLUSIONS

While the neurotrophin BDNF is equally present in PE and DIE, its receptors TrkB and p75 are more highly expressed in DIE and may have a potential role in the pathophysiology of DIE, especially in promotion of cell growth. BDNF has a stronger binding affinity than NGF to the p75 receptor, likely inducing sympathetic nerve axonal pruning in DIE, resulting in the lower nerve fiber density seen.

Nerve growth factor & TrkA as novel therapeutic targets in cancer

In the past 20years, nerve growth factor (NGF) and its receptors TrkA & p75NTR were recognized to be overexpressed in the overwhelming majority of human solid cancers. Recent studies discovered the presence of overactive TrkA signaling due to TrkA rearrangements or TrkA fusion products in frequent cancers like colorectal cancer, thyroid cancer, or acute myeloid leukemia. Thus, targeting TrkA/NGF via selective small-molecule-inhibitors or antibodies has gained enormous attention in the drug discovery sector. Clinical studies on the anti-cancer impact of NGF-blocking antibodies are likely to be accelerated after the recent removal of clinical holds on these agents by regulatory authorities. Based on these current developments, the present review provides not only a broad overview of the biological effects of NGF-TrkA-p75NTR on cancer cells and their microenvironment, but also explains why NGF and its receptors are going to evoke major interest as promising therapeutic anti-cancer targets in the coming decade.

Neurotrophin signaling in cancer stem cells

Cancer stem cells (CSCs), are thought to be at the origin of tumor development and resistance to therapies. Thus, a better understanding of the molecular mechanisms involved in the control of CSC stemness is essential to the design of more effective therapies for cancer patients. Cancer cell stemness and the subsequent expansion of CSCs are regulated by micro-environmental signals including neurotrophins. Over the years, the roles of neurotrophins in tumor development have been well established and regularly reviewed. Especially, nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) are reported to stimulate tumor cell proliferation, survival, migration and/or invasion, and favors tumor angiogenesis. More recently, neurotrophins have been reported to regulate CSCs. This review briefly presents neurotrophins and their receptors, summarizes their roles in different cancers, and discusses the emerging evidence of neurotrophins-induced enrichment of CSCs as well as the involved signaling pathways.

NGF-induced TrkA/CD44 association is involved in tumor aggressiveness and resistance to lestaurtinib

There is accumulating evidence that TrkA and its ligand Nerve Growth Factor (NGF) are involved in cancer development. Staurosporine derivatives such as K252a and lestaurtinib have been developed to block TrkA kinase signaling, but no clinical trial has fully demonstrated their therapeutic efficacy. Therapeutic failures are likely due to the existence of intrinsic signaling pathways in cancer cells that impede or bypass the effects of TrkA tyrosine kinase inhibitors. To verify this hypothesis, we combined different approaches including mass spectrometry proteomics, co-immunoprecipitation and proximity ligation assays. We found that NGF treatment induced CD44 binding to TrkA at the plasma membrane and subsequent activation of the p115RhoGEF/RhoA/ROCK1 pathway to stimulate breast cancer cell invasion. The NGF-induced CD44 signaling was independent of TrkA kinase activity. Moreover, both TrkA tyrosine kinase inhibition with lestaurtinib and CD44 silencing with siRNA inhibited cell growth in vitro as well as tumor development in mouse xenograft model; combined treatment significantly enhanced the antineoplastic effects of either treatment alone. Altogether, our results demonstrate that NGF-induced tyrosine kinase independent TrkA signaling through CD44 was sufficient to maintain tumor aggressiveness. Our findings provide an alternative mechanism of cancer resistance to lestaurtinib and indicate that dual inhibition of CD44 and TrkA tyrosine kinase activity may represent a novel therapeutic strategy.

Nerve Growth Factor Signals as Possible Pathogenic Biomarkers for Perineural Invasion in Adenoid Cystic Carcinoma

OBJECTIVE

The molecular mechanisms underlying perineural invasion (PNI)-a characteristic pathological feature of adenoid cystic carcinoma (ACC)-remain largely unclear. Recently, nerve growth factor (NGF) has been implicated in perineural invasion in certain malignancies. Overexpression of Myb related to the MYB-NFIB fusion gene in ACC has also been correlated with perineural invasion and survival. However, this concept is controversial. The aim of this study was to examine the expression of NGF together with its receptors, tropomyosin receptor kinase A (TrkA) and p75NRT, and Myb in ACC and assess their relationship with perineural invasion and survival.

STUDY DESIGN

Case series with chart review.

SETTING

The University of Tokyo Hospital.

SUBJECTS AND METHODS

We retrospectively analyzed 37 patients with ACC surgically treated from 1991 to 2011. We examined expression levels of NGF, TrkA, p75NRT, and Myb in the ACC specimens and their correlations with PNI and prognosis.

RESULTS

NGF, TrkA, p75NRT, and Myb overexpression rates were 65%, 65%, 30%, and 62%, respectively. Pearson product-moment correlation coefficient revealed a strong correlation between NGF/TrkA immunostaining and PNI (NGF: r = 0.68, P < .0001; TrkA: r = 0.53, P = .0007). Moreover, NGF overexpression was significantly associated with worse 8-year local control rate (27% vs 80%, P = .005). However, p75NRT and Myb expression was related to neither perineural invasion nor survival.

CONCLUSION

Our findings demonstrated that NGF and TrkA overexpression, but not Myb and p75NRT overexpression, may contribute to PNI and thus cause local recurrence in patients with ACC.

Human papillomavirus 16 infection predicts poor outcome in patients with esophageal squamous cell carcinoma

Background

Previous studies indicate that human papillomavirus 16 (HPV16) infection plays a pivotal role in the etiology of esophageal squamous cell carcinoma (ESCC). We aim to detect the influence of HPV16 infection on ESCC patient prognosis.

Patients and methods

Immunohistochemical staining for HPV16 E6 oncoprotein, the low-affinity p75 neurotrophin receptor (p75NTR), and phosphatidylinositol 3-kinase (PI3K) was performed on 103 archived surgical specimens from patients with ESCC and 54 control samples from patients with benign esophageal tumor or inflammatory lesions. All patients were from the Shaan Xi Province, People’s Republic of China.

Results

HPV16 E6 expression was significantly higher in the ESCC group (P<0.05). HPV16 E6 expression was significantly higher in men than in women (P<0.05). p75NTR expression was higher in those aged >56 years (P<0.05). PI3K expression was higher in those with a more advanced histopathological grade (P<0.05). There was a positive correlation between HPV16 E6 and p75NTR expression (r=0.547, P<0.001) and between p75NTR and PI3K expression (r=0.364, P<0.001). In 100 evaluable patients, the 5-year overall survival (OS) rate was 11%. In patients with ESCC, HPV16 E6 and PI3K expression were negatively correlated with the 3-year OS (P<0.05), 5-year OS (P<0.05), and progression-free survival (P<0.05).

Conclusion

HPV16 infection likely contributes to the etiology of ESCC patients in Shaan Xi, People’s Republic of China. HPV16 infection status and PI3K expression levels could be useful for predicting prognosis in patients with ESCC.

The oncogenic STP axis promotes triple-negative breast cancer via degradation of the REST tumor suppressor

Defining the molecular networks that drive breast cancer has led to therapeutic interventions and improved patient survival. However, the aggressive triple-negative breast cancer subtype (TNBC) remains recalcitrant to targeted therapies because its molecular etiology is poorly defined. In this study, we used a forward genetic screen to discover an oncogenic network driving human TNBC. SCYL1, TEX14, and PLK1 ("STP axis") cooperatively trigger degradation of the REST tumor suppressor protein, a frequent event in human TNBC. The STP axis induces REST degradation by phosphorylating a conserved REST phospho-degron and bridging REST interaction with the ubiquitin-ligase βTRCP. Inhibition of the STP axis leads to increased REST protein levels and impairs TNBC transformation, tumor progression, and metastasis. Expression of the STP axis correlates with low REST protein levels in human TNBCs and poor clinical outcome for TNBC patients. Our findings demonstrate that the STP-REST axis is a molecular driver of human TNBC.

NGF and ProNGF: Regulation of neuronal and neoplastic responses through receptor signaling

Nerve growth factor (NGF) and its precursor (proNGF) are primarily considered as regulators of neuronal function that induce their responses via the tyrosine kinase receptor TrkA and the pan-neurotrophin receptor p75NTR. It has been generally held that NGF exerts its effects primarily through TrkA, inducing a cascade of tyrosine kinase-initiated responses, while proNGF binds more strongly to p75NTR. When this latter entity interacts with a third receptor, sortilin, apoptotic responses are induced in contrast to the survival/differentiation associated with the other two. Recent studies have outlined portions of the downstream phosphoproteome of TrkA in the neuronal PC12 cells and have clarified the contribution of individual docking sites in the TrkA endodomain. The patterns observed showed a similarity with the profile induced by the epidermal growth factor receptor, which is extensively associated with oncogenesis. Indeed, as with other neurotrophic factors, the distribution of TrkA and p75NTR is not limited to neuronal tissue, thus providing an array of targets outside the nervous systems. One such source is breast cancer cells, in which NGF and proNGF stimulate breast cancer cell survival/growth and enhance cell invasion, respectively. This latter activity is exerted via TrkA (as opposed to p75NTR) in conjunction with sortilin. Another tissue overexpressing proNGF is prostate cancer and here the ability of cancer cells to induce neuritogenesis has been implicated in cancer progression. These studies show that the non-neuronal functions of proNGF/NGF are likely integrated with their neuronal activities and point to the clinical utility of these growth factors and their receptors as biomarkers and therapeutic targets for metastasis and cancer pain.

TrkB inhibition by GNF-4256 slows growth and enhances chemotherapeutic efficacy in neuroblastoma xenografts

PURPOSE

Neuroblastoma (NB) is one of the most common and deadly pediatric solid tumors. NB is characterized by clinical heterogeneity, from spontaneous regression to relentless progression despite intensive multimodality therapy. There is compelling evidence that members of the tropomyosin receptor kinase (Trk) family play important roles in these disparate clinical behaviors. Indeed, TrkB and its ligand, brain-derived neurotrophic factor (BDNF), are expressed in 50-60 % of high-risk NBs. The BDNF/TrkB autocrine pathway enhances survival, invasion, metastasis, angiogenesis and drug resistance.

METHODS

We tested a novel pan-Trk inhibitor, GNF-4256 (Genomics Institute of the Novartis Research Foundation), in vitro and in vivo in a nu/nu athymic xenograft mouse model to determine its efficacy in inhibiting the growth of TrkB-expressing human NB cells (SY5Y-TrkB). Additionally, we assessed the ability of GNF-4256 to enhance NB cell growth inhibition in vitro and in vivo, when combined with conventional chemotherapeutic agents, irinotecan and temozolomide (Irino-TMZ).

RESULTS

GNF-4256 inhibits TrkB phosphorylation and the in vitro growth of TrkB-expressing NBs in a dose-dependent manner, with an IC₅₀ around 7 and 50 nM, respectively. Furthermore, GNF-4256 inhibits the growth of NB xenografts as a single agent (p < 0.0001 for mice treated at 40 or 100 mg/kg BID, compared to controls), and it significantly enhances the antitumor efficacy of irinotecan plus temozolomide (Irino-TMZ, p < 0.0071 compared to Irino-TMZ alone).

CONCLUSIONS

Our data suggest that GNF-4256 is a potent and specific Trk inhibitor capable of significantly slowing SY5Y-TrkB growth, both in vitro and in vivo. More importantly, the addition of GNF-4256 significantly enhanced the antitumor efficacy of Irino-TMZ, as measured by in vitro and in vivo growth inhibition and increased event-free survival in a mouse xenograft model, without additional toxicity. These data strongly suggest that inhibition of TrkB with GNF-4256 can enhance the efficacy of current chemotherapeutic treatment for recurrent/refractory high-risk NBs with minimal or no additional toxicity.

Role of p38 MAP Kinase Signal Transduction in Solid Tumors

Mitogen-activated protein kinases (MAPKs) mediate a wide variety of cellular behaviors in response to extracellular stimuli. One of the main subgroups, the p38 MAP kinases, has been implicated in a wide range of complex biologic processes, such as cell proliferation, cell differentiation, cell death, cell migration, and invasion. Dysregulation of p38 MAPK levels in patients are associated with advanced stages and short survival in cancer patients (e.g., prostate, breast, bladder, liver, and lung cancer). p38 MAPK plays a dual role as a regulator of cell death, and it can either mediate cell survival or cell death depending not only on the type of stimulus but also in a cell type specific manner. In addition to modulating cell survival, an essential role of p38 MAPK in modulation of cell migration and invasion offers a distinct opportunity to target this pathway with respect to tumor metastasis. The specific function of p38 MAPK appears to depend not only on the cell type but also on the stimuli and/or the isoform that is activated. p38 MAPK signaling pathway is activated in response to diverse stimuli and mediates its function by components downstream of p38. Extrapolation of the knowledge gained from laboratory findings is essential to address the clinical significance of p38 MAPK signaling pathways. The goal of this review is to provide an overview on recent progress made in defining the functions of p38 MAPK pathways with respect to solid tumor biology and generate testable hypothesis with respect to the role of p38 MAPK as an attractive target for intervention of solid tumors.

AZ64 inhibits TrkB and enhances the efficacy of chemotherapy and local radiation in neuroblastoma xenografts

Neuroblastoma is a common pediatric tumor characterized by clinical heterogeneity. Because it is derived from sympathetic neuroblasts, the NTRK family of neurotrophin receptors plays an integral role in neuroblastoma cell survival, growth, and differentiation. Indeed, high expression of NTRK1 is associated with favorable clinical features and outcome, whereas expression of NTRK2 and its ligand, brain-derived neurotrophic factor (BDNF), are associated with unfavorable features and outcome. AZ64 (Astra Zeneca) is a potent and selective inhibitor of the NTRK tyrosine kinases that blocks phosphorylation at nanomolar concentrations. To determine the preclinical activity of AZ64, we performed intervention trials in a xenograft model with NTRK2-overexpressing neuroblastomas. AZ64 alone significantly inhibited tumor growth compared to vehicle-treated animals (p = 0.0006 for tumor size). Furthermore, the combination of AZ64 with conventional chemotherapeutic agents, irinotecan and temozolomide (irino-temo), showed significantly enhanced anti-tumor efficacy compared to irino-temo alone [(p < 0.0001 for tumor size, p < 0.0005 for event-free survival (EFS)]. We also assessed the combination of AZ64 and local radiation therapy (RT) on a neuroblastoma hindlimb xenograft model, and the efficacy of local RT was significantly increased when animals were treated simultaneously with AZ64 (p < 0.0001 for tumor size, p = 0.0006 for EFS). We conclude that AZ64 can inhibit growth of NTRK-expressing neuroblastomas both in vitro and in vivo. More importantly, it can significantly enhance the efficacy of conventional chemotherapy as well as local RT, presumably by inhibition of the NTRK2/BDNF autocrine survival pathway.

Pro-nerve growth factor induces autocrine stimulation of breast cancer cell invasion through tropomyosin-related kinase A (TrkA) and sortilin protein

The precursor of nerve growth factor (proNGF) has been described as a biologically active polypeptide able to induce apoptosis in neuronal cells, via the neurotrophin receptor p75(NTR) and the sortilin receptor. Herein, it is shown that proNGF is produced and secreted by breast cancer cells, stimulating their invasion. Using Western blotting and mass spectrometry, proNGF was detected in a panel of breast cancer cells as well as in their conditioned media. Immunohistochemical analysis indicated an overproduction of proNGF in breast tumors, when compared with benign and normal breast biopsies, and a relationship to lymph node invasion in ductal carcinomas. Interestingly, siRNA against proNGF induced a decrease of breast cancer cell invasion that was restored by the addition of non-cleavable proNGF. The activation of TrkA, Akt, and Src, but not the MAP kinases, was observed. In addition, the proNGF invasive effect was inhibited by the Trk pharmacological inhibitor K252a, a kinase-dead TrkA, and siRNA against TrkA sortilin, neurotensin, whereas siRNA against p75(NTR) and the MAP kinase inhibitor PD98059 had no impact. These data reveal the existence of an autocrine loop stimulated by proNGF and mediated by TrkA and sortilin, with the activation of Akt and Src, for the stimulation of breast cancer cell invasion.

Brain-derived neurotrophic factor and neurotrophin-4/5 are expressed in breast cancer and can be targeted to inhibit tumor cell survival

PURPOSE

Given that nerve growth factor has previously been shown to be involved in breast cancer progression, we have tested here the hypothesis that the other neurotrophins (NT) are expressed and have an influence in breast tumor growth.

EXPERIMENTAL DESIGN

The expression of brain-derived neurotrophic factor (BDNF), NT-3 and NT-4/5, as well as the neurotrophin receptor p75(NTR), TrkB, and TrkC, was studied by RT-PCR, Western blotting, and immunohistochemistry in cell lines and tumor biopsies. The biological impacts of neurotrophins, and associated mechanisms, were analyzed in cell cultures and xenografted mice.

RESULTS

BDNF and NT-4/5 were expressed and secreted by breast cancer cells, and the use of blocking antibodies suggested an autocrine loop mediating cell resistance to apoptosis. The corresponding tyrosine kinase receptor TrkB was only rarely observed at full length, whereas the expression of TrkB-T1, lacking the kinase domain, as well as p75(NTR), were detected in all tested breast cancer cell lines and tumor biopsies. In contrast, NT-3 and TrkC were not detected. SiRNA against p75(NTR) and TrkB-T1 abolished the antiapoptotic effect of BDNF and NT-4/5, whereas the pharmacological inhibitors K252a and PD98059 had no effect, suggesting the involvement of p75(NTR) and TrkB-T1, but not kinase activities from Trks and MAPK. In xenografted mice, anti-BDNF, anti-NT-4/5, anti-p75(NTR), or anti-TrkB-T1 treatments resulted in tumor growth inhibition, characterized by an increase in cell apoptosis, but with no change in proliferation.

CONCLUSION

BDNF and NT-4/5 contribute to breast cancer cell survival and can serve as prospective targets in attempts to inhibit tumor growth.

Nerve growth factor in cancer cell death and survival

One of the major challenges for cancer therapeutics is the resistance of many tumor cells to induction of cell death due to pro-survival signaling in the cancer cells. Here we review the growing literature which shows that neurotrophins contribute to pro-survival signaling in many different types of cancer. In particular, nerve growth factor, the archetypal neurotrophin, has been shown to play a role in tumorigenesis over the past decade. Nerve growth factor mediates its effects through its two cognate receptors, TrkA, a receptor tyrosine kinase and p75NTR, a member of the death receptor superfamily. Depending on the tumor origin, pro-survival signaling can be mediated by TrkA receptors or by p75NTR. For example, in breast cancer the aberrant expression of nerve growth factor stimulates proliferative signaling through TrkA and pro-survival signaling through p75NTR. This latter signaling through p75NTR promotes increased resistance to the induction of cell death by chemotherapeutic treatments. In contrast, in prostate cells the p75NTR mediates cell death and prevents metastasis. In prostate cancer, expression of this receptor is lost, which contributes to tumor progression by allowing cells to survive, proliferate and metastasize. This review focuses on our current knowledge of neurotrophin signaling in cancer, with a particular emphasis on nerve growth factor regulation of cell death and survival in cancer.

Mechanism of cancer pain

Ongoing and breakthrough pain is a primary concern for the cancer patient. Although the etiology of cancer pain remains unclear, animal models of cancer pain have allowed investigators to unravel some of the cancer-induced neuropathologic processes that occur in the region of tumor growth and in the dorsal horn of the spinal cord. Within the cancer microenvironment, cancer and immune cells produce and secrete mediators that activate and sensitize primary afferent nociceptors. Pursuant to these peripheral changes, nociceptive secondary neurons in spinal cord exhibit increased spontaneous activity and enhanced responsiveness to three modes of noxious stimulation: heat, cold, and mechanical stimuli. As our understanding of the peripheral and central mechanisms that underlie cancer pain improves, targeted analgesics for the cancer patient will likely follow.

Antitumor progression potential of caffeic acid phenethyl ester involving p75(NTR) in C6 glioma cells

The previous data showed that caffeic acid phenethyl ester (CAPE), a component of propolis, possesses inducing cell cycle arrest and antiproliferation effect on C6 glioma cells in vitro and in vivo. In the present study, C6 glioma cells treated with CAPE resulted in morphological changes to an astrocytic phenotype and increased the expression of glial differentiation marker proteins including glial fibrillary acidic protein (GFAP) and S-100β. In addition, with scratch assay and Boyden chamber assay, CAPE exhibited inhibitory effects on the motility and invasion of C6 glioma cells. Furthermore, CAPE induced the expression of nerve growth factor (NGF) and p75 neurotrophin receptor (p75(NTR)), which were involved in neural cell differentiation. CAPE could also inhibit the activity of matrix metalloproteinases (MMPs) and induce the expression of RhoB, a tumor suppressor. To examine the involvement of p75(NTR) in the anti-invasive property of CAPE, Western blotting and Boyden Chamber assay were performed by addition of an anti-p75(NTR) antibody in C6 cells. The results showed that blocking p75(NTR) could decrease the CAPE-induced expression of RhoB and the inactivation of MMP-2, -9 as well as the anti-invasion effect in C6 glioma cells. Furthermore, CAPE suppressed IκB-α phosphorylation which was down stream of p75(NTR). Finally, the effect of CAPE on metastasis by lung colonization of the tumor cell in nude mice was also evaluated. It was found that the groups of nude mice injected with CAPE-pretreated cells could decrease both lung size and weight as compared to the positive control group which did not receive CAPE treatment. In addition, histological examination of the mouse lung sections showed that the CAPE-treated group inhibited the metastasis of C6 glioma cells. These data suggest CAPE possesses antitumor progression potential.

Netrin-4 is upregulated in breast carcinoma effusions compared to corresponding solid tumors

We recently identified overexpression of the NTN4 gene in breast carcinoma effusions compared to primary carcinomas using gene-expression arrays. The objective of this study was to validate this finding at protein level and analyze the clinical role of Netrin-4 in breast carcinoma effusions. We additionally studied Netrin-4 expression and its clinical relevance in Müllerian (ovarian, peritoneal, and tubal) carcinoma effusions. Sections from 82 breast carcinomas (53 effusions and 29 solid tumors) and 57 Müllerian carcinoma effusions were stained for Netrin-4 using immunohistochemistry. Immunoreactivity was scored in carcinoma cells and analyzed for association with clinicopathologic parameters, including survival. In breast carcinoma, expression of Netrin-4 was detected in carcinoma cells in 30/53 (57%) effusions compared to 3/29 (10%) solid tumors (P < 0.001). Netrin-4 was further expressed in 31/57 (54%) Müllerian carcinoma effusions. No association was found between Netrin-4 expression in breast or Müllerian carcinoma effusions and clinicopathologic parameters, including survival. Our data provide validation on protein level of upregulated Netrin-4 expression in breast carcinoma effusions. The frequent expression of Netrin-4 in Müllerian carcinoma effusions suggests a biological role for this molecule in metastases from gynecological malignancies. Netrin-4 expression in effusions does not appear to be a predictor of disease outcome.

CD105 (Endoglin) expression in breast carcinoma effusions is a marker of poor survival

We analyzed the expression and clinical role of endoglin (CD105) in breast carcinoma effusions. Endoglin levels were measured in 36 effusion supernatants by ELISA and studied for association with the cancer-associated markers calprotectin, VEGF, and the VEGF receptor sFlt1. Endoglin expression was further studied in 46 effusions and 22 primary carcinomas using immunohistochemistry. The four secreted molecules were detected in all specimens and their levels significantly correlated (p < 0.001). In effusions, endoglin was localized to carcinoma cells and reactive mesothelium using immunohistochemistry. Tumor cell expression was higher in effusions compared to primary carcinomas (p = 0.025), and in post-chemotherapy compared to pre-chemotherapy effusions (p = 0.017). Higher tumor endoglin expression was associated with poor overall (p = 0.021) and disease-free (p = 0.032) survival in univariate analysis, and was an independent predictor in Cox multivariate analysis (p = 0.001 and p = 0.038, respectively). Our data suggest that endoglin may be an important therapeutic target in metastatic breast cancer.

Nerve growth factor and tyrosine kinase A receptor in oral squamous cell carcinoma: is there an association with perineural invasion?

PURPOSE

Perineural invasion (PNI) in oral squamous cell carcinoma (SCC) is recognized as a significant predictor of outcome. PNI is associated with locoregional recurrence and decreased survival of patients with head and neck SCC. Nerve growth factor (NGF) has been shown to be involved in PNI in several malignancies, including breast, prostate, and pancreatic cancers. We investigated the hypothesis that NGF and its high-affinity receptor tyrosine kinase A (TrkA) are highly expressed in cases of oral SCC that have histologic evidence of PNI.

MATERIALS AND METHODS

We performed immunohistochemistry on archived oral tongue SCC specimens from the established oral and general pathology databases at the University of California, San Francisco. The following groups were evaluated: 1) 21 T1/T2 oral tongue SCC cases with PNI and 2) 21 T1/T2 oral tongue SCC cases without histologic evidence of PNI.

RESULTS

Strong homogeneous cytoplasmic staining for NGF and TrkA was detected in the malignant cells in the PNI-positive group of tumors. In group II (PNI negative) NGF and TrkA were detected in the stroma cells or were very weakly expressed by the malignant cells. We were able to show the presence of NGF and TrkA in the cytoplasm of malignant squamous cells in tumors with histologic evidence of PNI. Immunostaining for NGF (P = .0001) and TrkA (P = .039) was significantly higher in the PNI-positive oral SCC group than in the PNI-negative oral SCC group.

CONCLUSION

This study shows that oral SCC with evidence of PNI shows increased expression of NGF and TrkA and suggests that NGF and TrkA are involved with the mechanism leading to PNI. Further investigations are warranted to determine the potential for use of NGF and TrkA as candidate biomarkers to predict progression and outcome.

Breast carcinoma cells in primary tumors and effusions have different gene array profiles

The detection of breast carcinoma cells in effusions is associated with rapidly fatal outcome, but these cells are poorly characterized at the molecular level. This study compared the gene array signatures of breast carcinoma cells in primary carcinomas and effusions. The genetic signature of 10 primary tumors and 10 effusions was analyzed using the Array-Ready Oligo set for the Human Genome platform. Results for selected genes were validated using PCR, Western blotting, and immunohistochemistry. Array analysis identified 255 significantly downregulated and 96 upregulated genes in the effusion samples. The majority of differentially expressed genes were part of pathways involved in focal adhesion, extracellular matrix-cell interaction, and the regulation of the actin cytoskeleton. Genes that were upregulated in effusions included KRT8, BCAR1, CLDN4, VIL2, while DCN, CLDN19, ITGA7, and ITGA5 were downregulated at this anatomic site. PCR, Western blotting, and immunohistochemistry confirmed the array findings for BCAR1, CLDN4, VIL2, and DCN. Our data show that breast carcinoma cells in primary carcinomas and effusions have different gene expression signatures, and differentially express a large number of molecules related to adhesion, motility, and metastasis. These differences may have a critical role in designing therapy and in prognostication for patients with metastatic disease localized to the serosal cavities.

Identification and preclinical characterization of AZ-23, a novel, selective, and orally bioavailable inhibitor of the Trk kinase pathway

Tropomyosin-related kinases (TrkA, TrkB, and TrkC) are receptor tyrosine kinases that, along with their ligands, the neurotrophins, are involved in neuronal cell growth, development, and survival. The Trk-neurotrophin pathway may also play a role in tumorigenesis through oncogenic fusions, mutations, and autocrine signaling, prompting the development of novel Trk inhibitors as agents for cancer therapy. This report describes the identification of AZ-23, a novel, potent, and selective Trk kinase inhibitor. In vitro studies with AZ-23 showed improved selectivity over previous compounds and inhibition of Trk kinase activity in cells at low nanomolar concentrations. AZ-23 showed in vivo TrkA kinase inhibition and efficacy in mice following oral administration in a TrkA-driven allograft model and significant tumor growth inhibition in a Trk-expressing xenograft model of neuroblastoma. AZ-23 represents a potent and selective Trk kinase inhibitor from a novel series with the potential for use as a treatment for cancer.

TrkA overexpression enhances growth and metastasis of breast cancer cells

The Trk family of neurotrophin tyrosine kinase receptors is emerging as an important player in carcinogenic progression in non-neuronal tissues. Here, we show that breast tumors present high levels of TrkA and phospho-TrkA compared to normal breast tissues. To further evaluate the precise functions of TrkA overexpression in breast cancer development, we have performed a series of biological tests using breast cancer cells that stably overexpress TrkA. We show that (1) TrkA overexpression promoted cell growth, migration and invasion in vitro; (2) overexpression of TrkA per se conferred constitutive activation of its tyrosine kinase activity; (3) signal pathways including PI3K-Akt and ERK/p38 MAP kinases were activated by TrkA overexpression and were required for the maintenance of a more aggressive cellular phenotype; and (4) TrkA overexpression enhanced tumor growth, angiogenesis and metastasis of xenografted breast cancer cells in immunodeficient mice. Moreover, recovered metastatic cells from the lungs exhibited enhanced anoikis resistance that was abolished by the pharmacological inhibitor K252a, suggesting that TrkA-promoted breast tumor metastasis could be mediated at least in part by enhancing anoikis resistance. Together, these results provide the first direct evidence that TrkA overexpression enhances the tumorigenic properties of breast cancer cells and point to TrkA as a potential target in breast cancer therapy.

Developmental and lactational exposure to dieldrin alters mammary tumorigenesis in Her2/neu transgenic mice

Breast cancer is the most common cancer in Western women and while its precise etiology is unknown, environmental factors are thought to play a role. The organochlorine pesticide dieldrin is a persistent environmental toxicant thought to increase the risk of breast cancer and reduce survival in the human population. The objective of this study was to define the effect of developmental exposure to environmentally relevant concentrations of dieldrin, on mammary tumor development in the offspring. Sexually mature FVB-MMTV/neu female mice were treated with vehicle (corn oil), or dieldrin (0.45, 2.25, and 4.5 µg/g body weight) daily by gavage for 5 days prior to mating and then once weekly throughout gestation and lactation until weaning. Dieldrin concentrations were selected to produce serum levels representative of human background body burdens, occupational exposure, and overt toxicity. Treatment had no effect on litter size, birth weight or the number of pups surviving to weaning. The highest dose of dieldrin significantly increased the total tumor burden and the volume and number of tumors found in the thoracic mammary glands. Increased mRNA and protein expression of the neurotrophin BDNF and its receptor TrkB was increased in tumors from the offspring of dieldrin treated dams. This study indicates that developmental exposure to the environmental contaminant dieldrin causes increased tumor burden in genetically predisposed mice. Dieldrin exposure also altered the expression of BNDF and TrkB, novel modulators of cancer pathogenesis.

Nerve growth factor receptor (p75 NTR) and pattern of invasion predict poor prognosis in oral squamous cell carcinoma

AIMS

To evaluate the expression of p75 neurotrophin receptor (p75(NTR)) in oral squamous cell carcinoma (OSCC). The results were related to tumour node metastasis (TNM) stage, World Health Organization (WHO) grade, invasive front grading (IFG) and prognosis.

METHODS AND RESULTS

Immunohistochemically, the expression of p75(NTR) was assessed in 53 T1-T2 OSCCs. Clinical data were recorded prospectively. The end-point was disease-free survival. All tumours expressed p75(NTR), and this expression, both in central/superficial tumour areas and at the invasive front, was associated with poor prognosis (P = 0.03 and P = 0.02) (log rank test). Tumours with marked cellular dissociation (IFG parameter) had more recurrences than tumours with collective tumour cell invasion (P = 0.03). In tumours showing both p75(NTR) at the invasive front and marked tumour cell dissociation, the average risk of recurrence was increased about 17 times (Cox regression analysis) compared with tumours with low p75(NTR) expression and collective invasion. Traditional prognostic systems were of no prognostic significance.

CONCLUSION

p75(NTR) was expressed in all OSCCs. p75(NTR) expression and the pattern of invasion were significantly associated with a poor prognosis in OSCCs, and both were better prognostic factors than traditional prognostic parameters. The combination of p75(NTR) expression and the pattern of invasion strongly increased precision in the identification of tumours with poor disease-free survival.

Expression of the chromatin remodeling factor Rsf-1 is down-regulated in breast carcinoma effusions

We recently identified Rsf-1, a chromatin-remodeling gene, as a potential oncogene that is frequently amplified and overexpressed in ovarian serous carcinoma, and demonstrated that its expression in carcinoma cells in effusions is associated with poor prognosis. In the present study, we assessed the clinical significance of Rsf-1 overexpression in breast carcinoma effusions. Formalin-fixed paraffin-embedded sections from 47 effusions were analyzed for Rsf-1 expression by immunohistochemistry. Matched primary tumors (n = 30) and solid metastases (n = 26) from 30 patients were additionally studied. Rsf-1 expression in tumor cells in effusions was analyzed for association with clinicopathologic parameters and survival. Rsf-1 protein expression was found in carcinoma cells in 34 (72%) of 47 effusions, 24 (80%) of 30 primary carcinomas, and 24 (92%) of 26 metastases. Rsf-1 immunoreactivity in effusions showed no association with HER-2 or hormone receptor status. Rsf-1 expression level was significantly lower in effusions compared with primary tumors (P = .026 and P = .011 for extent and intensity, respectively) and lymph node metastases (P = .023 and P = .013 for extent and intensity, respectively). Staining extent and intensity were both significantly lower in breast compared with ovarian carcinoma effusions (P = .001 for extent, P < .001 for intensity). Rsf-1 expression showed no association with survival. In conclusion, in contrast to ovarian carcinoma, Rsf-1 expression is down-regulated in breast carcinoma cells in effusions compared with the solid counterparts and has no prognostic role at this anatomic site.

The biological role of the low-affinity p75 neurotrophin receptor in esophageal squamous cell carcinoma

In this study, we investigated the clinicopathologic significance of the low-affinity p75 neurotrophin receptor (p75NTR; which is expressed in the stem/progenitor cell fraction of normal esophageal epithelial cells) in 187 resected esophageal squamous cell carcinoma (ESCC) specimens and found that approximately 50% of ESCC expressed p75NTR. Our investigation using ESCC cell lines showed that p75NTR was intensely expressed in the cells with high colony-forming capacity but they were sensitive to cell death on inhibition of p75NTR expression with transient transfection of small interfering RNA (siRNA). These findings suggest that p75NTR is necessary for survival and maintenance of ESCC tumors, providing us with a potential target for novel therapies.

PURPOSE

p75NTR is expressed in a stem/progenitor cell fraction of human normal esophageal epithelial cells. In this study, we investigated the expression and biological role of p75NTR in ESCC.

EXPERIMENTAL DESIGN

The expression of p75NTR in 187 resected ESCC specimens was immunohistochemically investigated. The expression of p75NTR in 30 ESCC cell lines (KYSEs) was assessed by reverse transcription-PCR, immunocytochemistry, and flow cytometry. The p75NTR-bright and p75NTR-dim/negative cells were isolated from KYSE150 by magnetic beads and colony formation was investigated. The role of p75NTR in KYSEs was assessed by transient transfection of siRNA.

RESULTS

p75NTR was expressed in 92 of 187 (49.2%) tumors. In well-differentiated tumors, positive staining was apparent in the first one to two layers from infiltrative margin of the tumors where most of the cells were actively proliferating. In moderately differentiated tumors, p75NTR was expressed in wider range from the margin of the tumors whereas p75NTR was diffusely distributed in poorly differentiated tumors. p75NTR was expressed in all examined KYSEs and the mean proportion of the p75NTR-bright fraction was 30.1%. The size of p75NTR-positive colonies was larger than that of p75NTR-negative colonies derived from KYSE150 (P<0.0001). The purified p75NTR-bright cells formed p75NTR-positive large colonies more frequently than the p75NTR-dim/negative cells (P<0.0001). Down-regulation of p75NTR expression by siRNA resulted in marked growth inhibition with induction of apoptosis.

CONCLUSIONS

Our findings suggest that p75NTR is necessary for survival and maintenance of ESCC tumors, providing us with a potential target for novel therapies.

Profiling genomic copy number changes in retinoblastoma beyond loss of RB1

Loss of both RB1 alleles is rate limiting for development of retinoblastoma (RB), but genomic copy number gain or loss may impact oncogene(s) and tumor suppressor genes, facilitating tumor progression. We used quantitative multiplex polymerase chain reaction to profile "hot spot" genomic copy number changes for gain at 1q32.1, 6p22, and MYCN, and loss at 16q22 in 87 primary RB and 7 cell lines. Loss at 16q22 (48%) negatively associated with MYCN gain (18%) (Fisher's exact P = 0.031), gain at 1q32.1 (62%) positively associated with 6p "hot spot" gain (43%) (P = 0.033), and there was a trend for positive association between 1q and MYCN gain (P = 0.095). Cell lines had a higher frequency of MYCN amplification than primary tumors (29% versus 3%; P = 0.043). Novel high-level amplification of 1q32.1 in one primary tumor, confirmed by fluorescence in situ hybridization, strongly supports the presence of oncogene(s) in this region, possibly the mitotic kinesin, KIF14. Gene-specific quantitative multiplex polymerase chain reaction of candidate oncogenes at 1q32.1 (KIF14), 6p22 (E2F3 and DEK), and tumor suppressor genes at 16q22 (CDH11) and 17q21 (NGFR) showed the most common gene gains in RB to be KIF14 in cell lines (80%) and E2F3 in primary tumors (70%). The patterns of gain/loss were qualitatively different in 25 RB compared with 12 primary hepatocellular carcinoma and 12 breast cancer cell lines. Gene specific analysis of one bone marrow metastasis of RB, prechemotherapy and postchemotherapy, showed the typical genomic changes of RB pretreatment, which normalized after chemotherapy.

A gene expression signature associated with metastatic cells in effusions of breast carcinoma patients

Malignant effusion in invasive breast carcinoma is associated with poor prognosis. To decipher molecular events leading to metastasis and to identify reliable markers for targeted therapies are of crucial need. Therefore, we have used cDNA microarrays to delineate molecular signatures associated with metastasis and relapse in breast carcinoma effusions. Taking advantage of an immunomagnetic method, we have purified to homogeneity EpCAM-positive cells from 34 malignant effusions. Immunopurified cells represented as much as 10% of the whole cell fraction and their epithelial and carcinoma features were confirmed by immunofluorescence labeling. Gene expression profiles of 19 immunopurified effusion samples, were analyzed using human pan-genomic microarrays, and compared with those of 4 corresponding primary tumors, 8 breast carcinoma effusion-derived cell lines, and 4 healthy mammary tissues. Principal component and multiple clustering analyses of microarray data, clearly identified distinctive molecular portraits corresponding to the 4 categories of specimens. Of uppermost interest, effusion samples were arranged in 2 subsets on the basis of their gene expression patterns. The first subset partly shares a gene expression signature with the different cell lines, and overexpresses CD24, CD44 and epithelial cytokeratins 8,18,19. The second subset overexpresses markers related to aggressive invasive carcinoma (uPA receptor, S100A4, vimentin, CXCR4). These findings demonstrate the importance of using pure cell fractions to accurately decipher in silico gene expression of clinical specimens. Further studies will lead to the identification of genes of oustanding importance to diagnose malignant effusion, predict survival and tailor appropriate therapies to the metastatic effusion disease in breast carcinoma patients.

Nerve growth factor receptor TrkA signaling in breast cancer cells involves Ku70 to prevent apoptosis

The nerve growth factor (NGF)-tyrosine kinase receptor TrkA plays a critical role in various neuronal and non-neuronal cell types by regulating cell survival, differentiation, and proliferation. In breast cancer cells, TrkA stimulation results in the activation of cellular growth, but downstream signaling largely remains to be described. Here we used a proteomics-based approach to identify partners involved in TrkA signaling in breast cancer cells. Wild type and modified TrkA chimeric constructs with green fluorescent protein were transfected in MCF-7 cells, and co-immunoprecipitated proteins were separated by SDS-PAGE before nano-LC-MS/MS analysis. Several TrkA putative signaling partners were identified among which was the DNA repair protein Ku70, which is increasingly reported for its role in cell survival and carcinogenesis. Physiological interaction of Ku70 with endogenous TrkA was induced upon NGF stimulation in non-transfected cells, and co-localization was observed with confocal microscopy. Mass spectrometry analysis and Western blotting of phosphotyrosine immunoprecipitates demonstrated the induction of Ku70 tyrosine phosphorylation upon NGF stimulation. Interestingly no interaction between TrkA and Ku70 was detected in PC12 cells in the absence or presence of NGF, suggesting that it is not involved in the initiation of neuronal differentiation. In breast cancer cells, RNA interference indicated that whereas Ku70 depletion had no direct effect on cell survival, it induced a strong potentiation of apoptosis in TrkA-overexpressing cells. In conclusion, TrkA signaling appears to be proapoptotic in the absence of Ku70, and this protein might therefore play a role in the long time reported ambivalence of tyrosine kinase receptors that can exhibit both anti- and eventually proapoptotic activities.