Endothelial Cells Promote Colorectal Cancer Cell Survival by Activating the HER3-AKT Pathway in a Paracrine Fashion

HER3: Unmasking a twist in the tale of a previously unsuccessful therapeutic pursuit targeting a key cancer survival pathway

HER3, formally referred to as ERB-B2 receptor tyrosine kinase 3, is a member of the ErbB receptor tyrosine kinases (also known as EGFR) family. HER3 plays a significant pro-cancer role in various types of cancer due to its overexpression and abnormal activation, which initiates downstream signaling pathways crucial in cancer cell survival and progression. As a result, numerous monoclonal antibodies have been developed to block HER3 activation and subsequent signaling pathways. While pre-clinical investigations have effectively showcased significant anti-cancer effects of HER3-targeted therapies, these therapies have had little impact on cancer patient outcomes in the clinic, except for patients with rare NRG1 fusion mutations. This review offers a comprehensive description of the oncogenic functions of HER3, encompassing its structure and mediating signaling pathways. More importantly, it provides an in-depth exploration of past and ongoing clinical trials investigating HER3-targeted therapies for distinct types of cancer and discusses the tumor microenvironment and other critical determinants that may contribute to the observed suboptimal outcomes in most clinical studies using HER3-targeted therapies. Lastly, we suggest alternative approaches and the exploration of novel strategies to potentially improve the efficacy of targeting the pivotal oncogenic HER3 signaling pathway in future translational investigations.

Cross-Talk Between Cancer and Its Cellular Environment-A Role in Cancer Progression

The tumor microenvironment is a dynamic and complex three-dimensional network comprising the extracellular matrix and diverse non-cancerous cells, including fibroblasts, adipocytes, endothelial cells and various immune cells (lymphocytes T and B, NK cells, dendritic cells, monocytes/macrophages, myeloid-derived suppressor cells, and innate lymphoid cells). A constantly and rapidly growing number of studies highlight the critical role of these cells in shaping cancer survival, metastatic potential and therapy resistance. This review provides a synthesis of current knowledge on the modulating role of the cellular microenvironment in cancer progression and response to treatment.

Leucine-Rich Alpha-2-Glycoprotein 1 Promotes Metastatic Colorectal Cancer Growth Through Human Epidermal Growth Factor Receptor 3 Signaling

BACKGROUND & AIMS

Therapy failure in patients with metastatic colorectal cancer (mCRC, ∼80% occur in the liver) remains an overarching challenge. Preclinical studies demonstrated that human epidermal growth factor receptor 3 (HER3) promotes colorectal cancer (CRC) cell survival, but therapies blocking the neuregulin-induced canonical HER3 signaling have made little impact in the clinic. Recent studies suggest that the liver microenvironment promotes CRC growth by activating HER3 in a neuregulin-independent fashion, thus elucidation of these mechanisms may reveal new strategies for treating patients with mCRC.

METHODS

Patient-derived primary liver endothelial cells (ECs) were used to interrogate EC-CRC crosstalk. We conducted proteomic analysis to identify EC-secreted factor(s) that triggers noncanonical HER3 activation in CRC and determined the subsequent effects on mCRC using diverse murine mCRC models. In vitro studies with genetic and pharmacological interventions were used to map the noncanonical HER3 pathway.

RESULTS

We demonstrated that EC-secreted leucine-rich alpha-2-glycoprotein 1 (LRG1) directly binds and activates HER3 and promotes CRC growth distinct from neuregulin, the canonical HER3 ligand. Blocking host-derived LRG1 by gene knockout or a neutralizing antibody impaired mCRC outgrowth in the liver and prolonged mouse survival. We identified protein synthesis activated by the PI3K-PDK1-RSK-eIF4B axis as the biologically relevant signaling cascade downstream of the LRG1-HER3 interaction, which was not blocked by conventional HER3-specific antibodies that failed in prior clinical trials.

CONCLUSIONS

LRG1 is a novel HER3 ligand and mediates liver-mCRC crosstalk. The LRG1-HER3 signaling axis is distinct from canonical HER3 signaling and represents a new therapeutic opportunity to treat patients with mCRC, and potentially other types of liver metastases.

Crosstalk between GLTSCR1-deficient endothelial cells and tumour cells promotes colorectal cancer development by activating the Notch pathway

Cancer stem cells (CSCs) typically reside in perivascular niches, but whether endothelial cells of blood vessels influence the stemness of cancer cells remains poorly understood. This study revealed that endothelial cell-specific GLTSCR1 deletion promotes colorectal cancer (CRC) tumorigenesis and metastasis by increasing cancer cell stemness. Mechanistically, knocking down GLTSCR1 induces the transformation of endothelial cells into tip cells by regulating the expression of Neuropilin-1 (NRP1), thereby increasing the direct contact and interaction between endothelial cells and tumour cells. In addition, GLTSCR1 inhibits JAG1 transcription by competing with acetylated p65(Lys-310) to bind to the BRD4 interaction site. Therefore, GLTSCR1 deficiency increases JAG1 expression in endothelial cells. Subsequently, increased JAG1 levels on tip cell membranes bind to Notch on CRC cell membranes, activating the Notch signalling pathway in tumour cells and increasing CRC cell stemness. Taken together, our findings highlight the roles of endothelial cells in CRC development.

Longitudinal tracking of circulating rare events in the liquid biopsy of stage III-IV non-small cell lung cancer patients

In the United States, lung cancer is the second most common type of cancer with non-small cell lung cancer (NSCLC) encompassing around 85% of total lung cancer cases. Late-stage patients with metastatic disease have worsening prognosis, highlighting the importance of longitudinal disease monitoring. Liquid biopsy (LBx) represents a way for physicians to non-invasively track tumor analytes, such as circulating tumor cells (CTCs), and understand tumor progression in real-time through analyzing longitudinal blood samples. CTCs have been shown to be effective predictive biomarkers in measuring treatment efficacy and survival outcomes. We used the third-generation High-Definition Single Cell Assay (HDSCA3.0) workflow to analyze circulating rare events longitudinally during treatment in a cohort of 10 late-stage NSCLC patients, identifying rare events including circulating cancer cells (i.e., CTCs), and oncosomes. Here, we show (1) that there is a cancer specific LBx profile, (2) there is considerable heterogeneity of rare cells and oncosomes, and (3) that LBx data elements correlated with patient survival outcomes. Additional studies are warranted to understand the biological significance of the rare events detected, and the clinical potential of the LBx to monitor and predict response to treatment in NSCLC patient care.

Tumor Microenvironment: A Niche for Cancer Stem Cell Immunotherapy

Tumorigenic Cancer Stem Cells (CSCs), often called tumor-initiating cells (TICs), represent a unique subset of cells within the tumor milieu. They stand apart from the bulk of tumor cells due to their exceptional self-renewal, metastatic, and differentiation capabilities. Despite significant progress in classifying CSCs, these cells remain notably resilient to conventional radiotherapy and chemotherapy, contributing to cancer recurrence. In this review, our objective is to explore novel avenues of research that delve into the distinctive characteristics of CSCs within their surrounding tumor microenvironment (TME). We will start with an overview of the defining features of CSCs and then delve into their intricate interactions with cells from the lymphoid lineage, namely T cells, B cells, and natural killer (NK) cells. Furthermore, we will discuss their dynamic interplay with myeloid lineage cells, including macrophages, neutrophils, and myeloid-derived suppressor cells (MDSCs). Moreover, we will illuminate the crosstalk between CSCs and cells of mesenchymal origin, specifically fibroblasts, adipocytes, and endothelial cells. Subsequently, we will underscore the pivotal role of CSCs within the context of the tumor-associated extracellular matrix (ECM). Finally, we will highlight pre-clinical and clinical studies that target CSCs within the intricate landscape of the TME, including CAR-T therapy, oncolytic viruses, and CSC-vaccines, with the ultimate goal of uncovering novel avenues for CSC-based cancer immunotherapy.

Crosstalk between Endothelial Cells and Tumor Cells: A New Era in Prostate Cancer Progression

Prostate cancer stands as one of the most prevalent malignancies afflicting men worldwide. The tumor microenvironment plays a pivotal role in tumor progression, comprising various cell types including endothelial cells, tumor-associated fibroblasts, and macrophages. Recent accumulating evidence underscores the indispensable contribution of endothelial cells to prostate cancer development. Both endothelial cells and tumor cells release a multitude of factors that instigate angiogenesis, metastasis, and even drug resistance in prostate cancer. These factors serve as regulators within the tumor microenvironment and represent potential therapeutic targets for managing prostate cancer. In this review, we provide an overview of the crucial functions of endothelial cells in angiogenesis, metastasis, and drug resistance, and their prospective therapeutic applications in combating this disease.

PI3K/Akt signaling in urological cancers: Tumorigenesis function, therapeutic potential, and therapy response regulation

In addition to environmental conditions, lifestyle factors, and chemical exposure, aberrant gene expression and mutations involve in the beginning and development of urological tumors. Even in Western nations, urological malignancies are among the top causes of patient death, and their prevalence appears to be gender dependent. The prognosis for individuals with urological malignancies remains dismal and unfavorable due to the ineffectiveness of conventional treatment methods. PI3K/Akt is a popular biochemical mechanism that is activated in tumor cells as a result of PTEN loss. PI3K/Akt escalates growth and metastasis. Moreover, due to the increase in tumor cell viability caused by PI3K/Akt activation, cancer cells may acquire resistance to treatment. This review article examines the function of PI3K/Akt in major urological tumors including bladder, prostate, and renal tumors. In prostate, bladder, and kidney tumors, the level of PI3K and Akt are notably elevated. In addition, the activation of PI3K/Akt enhances the levels of Bcl-2 and XIAP, hence increasing the tumor cell survival rate. PI3K/Akt ] upregulates EMT pathways and matrix metalloproteinase expression to increase urological cancer metastasis. Furthermore, stimulation of PI3K/Akt results in drug- and radio-resistant cancers, but its suppression by anti-tumor drugs impedes the tumorigenesis.

Vincristine Enhances the Efficacy of MEK Inhibitors in Preclinical Models of KRAS-mutant Colorectal Cancer

Mutations in KRAS are found in more than 50% of tumors from patients with metastatic colorectal cancer (mCRC). However, direct targeting of most KRAS mutations is difficult; even the recently developed KRASG12C inhibitors failed to show significant benefit in patients with mCRC. Single agents targeting mitogen-activated protein kinase kinase (MEK), a downstream mediator of RAS, have also been ineffective in colorectal cancer. To identify drugs that can enhance the efficacy of MEK inhibitors, we performed unbiased high-throughput screening using colorectal cancer spheroids. We used trametinib as the anchor drug and examined combinations of trametinib with the NCI-approved Oncology Library version 5. The initial screen, and following focused validation screens, identified vincristine as being strongly synergistic with trametinib. In vitro, the combination strongly inhibited cell growth, reduced clonogenic survival, and enhanced apoptosis compared with monotherapies in multiple KRAS-mutant colorectal cancer cell lines. Furthermore, this combination significantly inhibited tumor growth, reduced cell proliferation, and increased apoptosis in multiple KRAS-mutant patient-derived xenograft mouse models. In vivo studies using drug doses that reflect clinically achievable doses demonstrated that the combination was well tolerated by mice. We further determined that the mechanism underlying the synergistic effect of the combination was due to enhanced intracellular accumulation of vincristine associated with MEK inhibition. The combination also significantly decreased p-mTOR levels in vitro, indicating that it inhibits both RAS-RAF-MEK and PI3K-AKT-mTOR survival pathways. Our data thus provide strong evidence that the combination of trametinib and vincristine represents a novel therapeutic option to be studied in clinical trials for patients with KRAS-mutant mCRC.

SIGNIFICANCE

Our unbiased preclinical studies have identified vincristine as an effective combination partner for the MEK inhibitor trametinib and provide a novel therapeutic option to be studied in patients with KRAS-mutant colorectal cancer.

HER3- A key survival pathway and an emerging therapeutic target in metastatic colorectal cancer and pancreatic ductal adenocarcinoma

Colorectal cancer (CRC) and pancreatic ductal adenocarcinoma (PDAC) are highly metastatic cancers with poor survival rates. The tumor microenvironment has been shown to play a critical role in cancer progression and response to therapies. Endothelial cells (ECs) are a key component of the tumor microenvironment and promote cancer cell survival by secreting soluble factors that activate cancer-promoting signaling pathways. Studies from us and others identified HER3 as a key mediator of liver EC-induced chemoresistance and cancer cell growth in metastatic CRC and PDAC. In this article, we discuss that HER3-targeted therapies may be effective in treating patients with HER3-expressing CRC and PDAC, and highlight the importance of applying HER3 expression as a predictive biomarker for patient response to HER3-targeted therapies. We also discuss the challenges encountered in past clinical trials of HER3-targeted therapies, including the role of NRG1 gene fusions, alternative HER3 activation mechanisms, and adaptive resistance mechanisms. Finally, we conclude by suggesting the future directions of HER3-targeted therapies, including novel approaches to overcome chemoresistance and promote cancer cell death.

Combining MEK and SRC inhibitors for treatment of colorectal cancer demonstrate increased efficacy in vitro but not in vivo

Metastatic colorectal cancer (mCRC) is the second leading cause of cancer deaths in the United States. More than 50% of patients with mCRC harbor mutations of the oncogenic driver RAS (KRAS or NRAS). Because directly targeting most mutations of RAS is technically challenging, researchers have concentrated on targeting MEK, a downstream mediator of RAS. However, targeting MEK as single-agent therapy is ineffective in patients with mCRC. We hypothesize that combining a MEK inhibitor with other agents can enhance the efficacy of MEK targeting in mCRC. Unbiased high-throughput screening (HTS) was performed to identify drugs that enhance the efficacy of MEK inhibitors. HTS was performed with KRAS-mutated CRC cells using the MEK inhibitor trametinib as a "backbone" and two "clinically ready" compound libraries approved by the U.S. Food and Drug Administration or in clinical trials. HTS demonstrated that the combination of the SRC inhibitor dasatinib and trametinib was synergistic in CRC cells in vitro (MTT and colony formation assays). Analysis of markers for cell proliferation and apoptosis using fluorescence-activated cell sorting, reverse-phase protein array, or Western blotting demonstrated decreased cell proliferation and increased cell death when targeting both SRC and MEK as compared to single agents in multiple CRC cell lines. However, combining dasatinib and trametinib in vivo at doses in mice equivalent to doses used in humans failed to significantly enhance the antitumor activity of trametinib when compared to that of trametinib alone. These results underscore the importance of performing careful preclinical in vivo validation studies using clinically relevant doses as a prerequisite for translating in vitro findings to the clinic.

Ecological niches for colorectal cancer stem cell survival and thrival

To date, colorectal cancer is still ranking top three cancer types severely threatening lives. According to cancer stem cell hypothesis, malignant colorectal lumps are cultivated by a set of abnormal epithelial cells with stem cell-like characteristics. These vicious stem cells are derived from intestinal epithelial stem cells or transformed by terminally differentiated epithelial cells when they accumulate an array of transforming genomic alterations. Colorectal cancer stem cells, whatever cell-of-origin, give rise to all morphologically and functionally heterogenous tumor daughter cells, conferring them with overwhelming resilience to intrinsic and extrinsic stresses. On the other hand, colorectal cancer stem cells and their daughter cells continuously participate in constructing ecological niches for their survival and thrival by communicating with adjacent stromal cells and circulating immune guardians. In this review, we first provide an overview of the normal cell-of-origin populations contributing to colorectal cancer stem cell reservoirs and the niche architecture which cancer stem cells depend on at early stage. Then we survey recent advances on how these aberrant niches are fostered by cancer stem cells and their neighbors. We also discuss recent research on how niche microenvironment affects colorectal cancer stem cell behaviors such as plasticity, metabolism, escape of immune surveillance as well as resistance to clinical therapies, therefore endowing them with competitive advantages compared to their normal partners. In the end, we explore therapeutic strategies available to target malignant stem cells.

Tumor microenvironment enriches the stemness features: the architectural event of therapy resistance and metastasis

Cancer divergence has many facets other than being considered a genetic term. It is a tremendous challenge to understand the metastasis and therapy response in cancer biology; however, it postulates the opportunity to explore the possible mechanism in the surrounding tumor environment. Most deadly solid malignancies are distinctly characterized by their tumor microenvironment (TME). TME consists of stromal components such as immune, inflammatory, endothelial, adipocytes, and fibroblast cells. Cancer stem cells (CSCs) or cancer stem-like cells are a small sub-set of the population within cancer cells believed to be a responsible player in the self-renewal, metastasis, and therapy response of cancer cells. The correlation between TME and CSCs remains an enigma in understanding the events of metastasis and therapy resistance in cancer biology. Recent evidence suggests that TME dictates the CSCs maintenance to arbitrate cancer progression and metastasis. The immune, inflammatory, endothelial, adipocyte, and fibroblast cells in the TME release growth factors, cytokines, chemokines, microRNAs, and exosomes that provide cues for the gain and maintenance of CSC features. These intricate cross-talks are fueled to evolve into aggressive, invasive, migratory phenotypes for cancer development. In this review, we have abridged the recent developments in the role of the TME factors in CSC maintenance and how these events influence the transition of tumor progression to further translate into metastasis and therapy resistance in cancer.

Liver Endothelium Microenvironment Promotes HER3-mediated Cell Growth in Pancreatic Ductal Adenocarcinoma

~90% metastatic pancreatic ductal adenocarcinoma (mPDAC) occurs in the liver, and the 5-year survival rate for patients with mPDAC is only at 3%. The liver has a unique endothelial cell (EC)-rich microenvironment, and preclinical studies showed that ECs promote cancer cell survival pathways by secreting soluble factors in a paracrine fashion in other types of cancer. However, the effects of liver ECs on mPDAC have not been elucidated. In this study, we used primary liver ECs and determined that liver EC-secreted factors containing conditioned medium (CM) increased PDAC cell growth, compared to control CM from PDAC cells. Using an unbiased receptor tyrosine kinase array, we identified human epidermal growth factor receptor 3 (HER3, also known as ErbB3) as a key mediator of liver EC-induced growth in PDAC cells with HER3 expression (HER3 +ve). We found that EC-secreted neuregulins activated the HER3-AKT signaling axis, and that depleting neuregulins from EC CM or blocking HER3 with an antibody, seribantumab, attenuated EC-induced functions in HER3 +ve PDAC cells, but not in cells without HER3 expression. Furthermore, we determined that EC CM increased PDAC xenograft growth in vivo, and that seribantumab blocked EC-induced growth in xenografts with HER3 expression. These findings elucidated a paracrine role of liver ECs in promoting PDAC cell growth, and identified the HER3-AKT axis as a key mediator in EC-induced functions in HER3 +ve PDAC cells. As over 70% mPDAC express HER3, this study highlights the potential of using HER3-targeted therapies for treating patients with HER3 +ve mPDAC.

Tumor Microenvironment Shapes Colorectal Cancer Progression, Metastasis, and Treatment Responses

Colorectal cancer (CRC) is one of the most devastating diseases that accounts for numerous deaths worldwide. Tumor cell-autonomous pathways, such as the oncogenic signaling activation, significantly contribute to CRC progression and metastasis. Recent accumulating evidence suggests that the CRC microenvironment also profoundly promotes or represses this process. As the roles of the tumor microenvironment (TME) in CRC progression and metastasis is gradually uncovered, the importance of these non-cell-autonomous signaling pathways is appreciated. However, we are still at the beginning of this TME function exploring process. In this review, we summarize the current understanding of the TME in CRC progression and metastasis by focusing on the gut microbiota and host cellular and non-cellular components. We also briefly discuss TME-remodeling therapies in CRC.

Liver Endothelium Promotes HER3-mediated Cell Survival in Colorectal Cancer with Wild-type and Mutant KRAS

We previously identified that human epidermal growth factor receptor 3 (HER3, also known as ERBB3) is a key mediator in liver endothelial cell (EC) promoting colorectal cancer (CRC) growth and chemoresistance, and suggested HER3-targeted therapy as a strategy for treating patients with metastatic CRC (mCRC) in the liver. Meanwhile, KRAS mutations occur in 40-50% of mCRC and render CRC resistant to therapies targeting the other HER family protein epidermal growth factor receptor (EGFR). It is necessary to elucidate the roles of KRAS mutation status in HER3-mediated cell survival and CRC response to HER3 inhibition. In the present study, we used primary ECs isolated from non-neoplastic liver tissues to recapitulate the liver EC microenvironment. We demonstrated that liver EC-secreted factors activated CRC-associated HER3, and increased CRC cell survival in vitro and promoted CRC patient-derived xenograft tumor growth in vivo. Moreover, we determined that blocking HER3, either by siRNA knockdown or the humanized antibody seribantumab, blocked EC-induced CRC survival in vitro in both KRAS wild-type and mutant CRC cells, and the HER3 antibody seribantumab significantly decreased CRC tumor growth and sensitized tumors to chemotherapy in an orthotopic xenograft model with CRC tumors developed in the liver. In summary, our findings demonstrated that blocking HER3 had significant effects on attenuating liver EC-induced CRC cell survival independent of the KRAS mutation status. Implications: This body of work highlighted a potential strategy of using HER3 antibodies in combination with standard chemotherapy agents for treating patients with either KRAS wild-type or KRAS mutant mCRC.

Human umbilical vein endothelial cells derived-exosomes promote osteosarcoma cell stemness by activating Notch signaling pathway

Osteosarcoma is one of the most common primary malignant tumors of bone in adolescents. Human umbilical vein endothelial cells (HUVECs) derived exosomes are associated with osteosarcoma cell stemness. Little is known about the function of HUVECs-exosomes in osteosarcoma cell stemness. This work aimed to investigate the mechanism of action of HUVECs-exosomes in regulating stem cell-like phenotypes of osteosarcoma cells. HUVECs were treated with GW4869 (exosome inhibitor). Human osteosarcoma cells (U2OS and 143B) were treated with HUVECs supernatant, HUVECs-exosomes with or without RO4929097 (γ secretase inhibitor, used to block Notch signaling pathway). We found that HUVECs supernatant and HUVECs-exosomes enhanced the proportions of STRO-1⁺CD117⁺ cells and the expression of stem cell-related proteins Oct4 and Sox2. Both HUVECs supernatant and HUVECs-exosomes promoted the sarcosphere formation efficiency of U2OS and 143B cells. These stem-like phenotypes of U2OS and 143B cells conferred by HUVECs-exosomes were repressed by GW4869. Moreover, HUVECs-exosomes promoted the expression of Notch1, Hes1 and Hey1 in the U2OS and 143B cells. RO4929097 treatment reversed the impact of HUVECs-exosomes on Notch1, Hes1, and Hey1 expression by inhibiting Notch1 signaling pathway. In conclusion, this work demonstrated that HUVECs-exosomes promoted cell stemness in osteosarcoma through activating Notch signaling pathway. Thus, our data reveal the mechanism of HUVECs-exosomes in regulating cell stemness of osteosarcoma, and provide a theoretical basis for osteosarcoma treatment by exosomes.

Endothelial Cells Promote Docetaxel Resistance of Prostate Cancer Cells by Inducing ERG Expression and Activating Akt/mTOR Signaling Pathway

Docetaxel is a first-line chemotherapy for the treatment of patients with castration-resistant prostate cancer (CRPC). Despite the good initial response of docetaxel, drug resistance will inevitably occur. Mechanisms underlying docetaxel resistance are not well elaborated. Endothelial cells (ECs) have been implicated in the progression and metastasis of prostate cancer. However, little attention has been paid to the role of endothelial cells in the development of docetaxel resistance in prostate cancer. Here, we sought to investigate the function and mechanism of endothelial cells involving in the docetaxel resistance of prostate cancer. We found that endothelial cells significantly promoted the proliferation of prostate cancer cells and decreased their sensitivity to docetaxel. Mechanistically, basic fibroblast growth factor (FGF2) secreted by endothelial cells leads to the upregulation of ETS related gene (ERG) expression and activation of the Akt/mTOR signaling pathway in prostate cancer cells to promote docetaxel resistance. In summary, these findings demonstrate a microenvironment-dependent mechanism mediating chemoresistance of prostate cancer and suggest that targeting FGF/FGFR signaling might represent a promising therapeutic strategy to overcome docetaxel resistance.

Correlation of PRL3 expression with colorectal cancer progression

OBJECTIVES

To evaluate the relationship between phosphatase of regenerating liver 3 (PRL3) expression and clinical outcome in colorectal cancer (CRC).

BACKGROUND

PRL3, a protein tyrosine phosphatase functions as one of the key regulatory enzymes of various signal transduction pathways. PRL3 is highly expressed in a majority of cancers and is a novel potential therapeutic target.

METHODS

PRL3 expression was evaluated by immunohistochemistry in 167 patients with CRC, 37 patients with no disease, and 26 patients with metastatic CRC (mCRC). Phosphorylated Akt at serine 473 (p-Akt S473) expression was also evaluated by immunohistochemistry in mCRC patients.

RESULTS

High expression of PRL3 was correlated with CRC progression, and every one unit increase in PRL3 level contributed to an increase in the rate of death by 1%-1.7%. PRL3 expression was significantly higher in liver metastases compared with primary tumors and showed a significant positive correlation with the expression level of p-Akt S473.

CONCLUSION

PRL3 expression levels associated with CRC progression and metastasis, and positively correlated with activated Akt level in mCRC. Together, these findings indicated that PRL3 might be a potential marker for increased risk of CRC-specific tumor burden and identify PRL3 as an attractive therapeutic target for mCRC treatment.

Exploring the radiosensitizing potential of AZD8931: a pilot study on the human LoVo colorectal cancer cell line

AIM

To explore the radiosensitizing effect of AZD8931, a novel equipotent and reversible inhibitor of signaling by EGFR (HER1), HER2 and HER3 receptors, focusing on cell cycle progression, apoptosis and clonogenic capacity in the human LoVo colorectal cancer (CRC) cell line, also in comparison with the EGFR-blocking monoclonal antibody Cetuximab or the EGFR tyrosine kinase selective small molecular inhibitor Gefitinib.

MATERIALS AND METHODS

Cells were pretreated with EGFR inhibitors for 5 consecutive days and then exposed or not to ionizing radiation (IR) (2 Gy daily for 3 consecutive days). Cell proliferation, cell cycle progression and apoptosis were evaluated by flow cytometry and enzyme-linked immunosorbent assay (ELISA), clonogenic potential and radiosensitivity were studied by colony formation assay.

RESULTS

AZD8931 induced cell cycle arrest and apoptosis more effectively than Gefitinib and Cetuximab and, more importantly, it was significantly more potent than Gefitinib and Cetuximab in radiosensitizing cells. This radiosensitizing action by AZD8931 mainly occurred by markedly reducing cell cycle progression into S phase, the most radioresistant phase of cell cycle, secondly by inducing apoptosis and reducing clonogenic survival.

CONCLUSIONS

Our results show that AZD8931 increases IR efficacy in LoVo cells, suggesting that it works as a potent radiosensitizer, even more efficient than Gefitinib and Cetuximab, opening new pathways of investigation for further in vitro and in vivo studies aimed at confirming its potential to improve local radiotherapy in CRC.

High-Throughput Tumor-on-a-Chip Platform to Study Tumor-Stroma Interactions and Drug Pharmacokinetics

Drug screening in oncology, especially for triple-negative breast cancer (TNBC), has high demand but remains unsatisfactory. Currently available models are either nonrepresentative of the complex tumor microenvironment or only suitable for low throughput screening, resulting in a low-yield success for drug development. To tackle these issues, the L-TumorChip system is developed in this study. It is a three-layered microfluidic tumor-on-a-chip platform integrating tumor microvasculature and tumor-stromal microenvironment with high throughput screening capability. Its layered and modular design is readily scalable through simple integration of multiple units. Here, L-TumorChip is validated with a TNBC model. The L-TumorChip system emulates certain tumor-stroma complexities and tumor-endothelium interactions, including TNBC invasion through the leaky microvasculature and angiogenesis. Additionally, with this L-TumorChip, the influence of different stromal cells, including normal fibroblasts, mesenchymal stem cells, and cancer-associated fibroblasts (CAF), on cancer cell growth as well as the stromal effects on drug responses to doxorubicin treatment is investigated. The presence of CAF delays drug pharmacokinetics, while apoptotic responses indicated by caspase-3 activities are higher in coculture with normal fibroblasts. Collectively, the L-TumorChip system represents a translational high-throughput screening toolkit that enables drug screening with a scenario closer to the in vivo conditions. This potential use may therefore facilitate development of new cancer drugs.

Tumor microenvironment in gastric cancers

The tumor microenvironment favors the growth and expansion of cancer cells. Many cell types are involved in the tumor microenvironment such as inflammatory cells, fibroblasts, nerves, and vascular endothelial cells. These stromal cells contribute to tumor growth by releasing various molecules to either directly activate the growth signaling in cancer cells or remodel surrounding areas. This review introduces recent advances in findings on the interactions within the tumor microenvironment such as in cancer-associated fibroblasts (CAFs), immune cells, and endothelial cells, in particular those established in mouse gastric cancer models. In mice, myofibroblasts in the gastric stroma secrete R-spondin and support normal gastric stem cells. Most CAFs promote tumor growth in a paracrine manner, but CAF population appears to be heterogeneous in terms of their function and origin, and include both tumor-promoting and tumor-restraining populations. Among immune cell populations, tumor-associated macrophages, including M1 and M2 macrophages, and myeloid-derived suppressor cells (MDSCs), are reported to directly or indirectly promote gastric tumorigenesis by secreting soluble factors or modulating immune responses. Endothelial cells or blood vessels not only fuel tumors with nutrients, but also interact with cancer stem cells and immune cells by secreting chemokines or cytokines, and act as a cancer niche. Understanding these interactions within the tumor microenvironment would contribute to unraveling new therapeutic targets.

Endothelial cells in colorectal cancer

The dependence of tumor growth on neovascularization has become an important aspect of cancer biology. Tumor angiogenesis is one of the key mechanisms of tumorigenesis, growth and metastasis. The key events involved in this process are endothelial cell proliferation, migration, and vascular formation. Recent studies have revealed the importance of tumor-associated endothelial cells (TECs) in the development and progression of colorectal cancer (CRC), including epithelial proliferation, stem cell maintenance, angiogenesis, and immune remodeling. Decades of research have identified that the molecular basis of tumor angiogenesis includes vascular endothelial growth factors (VEGFs) and their receptor family, which are the main targets of antiangiogenesis therapy. VEGFs and their receptors play key roles in the pathology of angiogenesis, and their overexpression indicates poor prognosis in CRC. This article reviews the characteristics of the tumor vasculature and the role of TECs in different stages of CRC and immune remodeling. We also discuss the biological effects of VEGFs and their receptor family as angiogenesis regulators and emphasize the clinical implications of TECs in clinical treatment.