Epidermal growth factor inhibits Ca(2+)-dependent Cl- transport in T84 human colonic epithelial cells

Effects of orally administered crofelemer on the incidence and severity of neratinib-induced diarrhea in female dogs

Targeted therapies have increased cancer therapy-related diarrhea (CTD) burden, with high incidence and/or severity of diarrhea for some agents that inhibit epidermal growth factor receptor and receptor tyrosine kinases. Neratinib is a pan-HER tyrosine kinase inhibitor approved for breast cancer treatment and causes severe diarrhea in >95% of patients. Crofelemer, a novel intestinal chloride ion channel modulator, is an approved antidiarrheal drug for symptomatic relief of noninfectious diarrhea in patients with HIV/AIDS receiving antiretroviral therapy. The objective of this study was to evaluate the effectiveness of crofelemer prophylaxis in reducing the incidence /severity of neratinib-induced diarrhea without concomitant administration of loperamide in female beagle dogs. A pilot study using 3 dogs determined a maximum daily tolerated dose of neratinib was between 40 and 80 mg; this dose would induce a consistent incidence/severity of diarrhea without risking severe dehydration. In the definitive study, 24 female beagle dogs (8/group) received neratinib once daily and placebo capsules (CTR) four times/day, or neratinib once daily and crofelemer 125 mg delayed-release tablets given two times (BID), or neratinib once daily and crofelemer 125 mg delayed-release tablets given four times per day (QID). Fecal scores were collected twice daily using an established canine stool scoring scale called the Purina Fecal Scoring (PFS) System. After 28 days, using analysis of covariance (ANCOVA), dogs in the CTR group had a significantly higher average number of weekly loose/watery stools (PFS of 6 or 7) when compared to either crofelemer BID (8.71±2.2 vs. 5.96±2.2, p = 0.028) or crofelemer QID (8.70±2.2 vs. 5.74±2.2, p = 0.022) treatment groups. The average number of weekly loose/watery stools were not different between the crofelemer BID and QID treatment groups (p = 0.84). This study showed that crofelemer prophylaxis reduced the incidence/severity of neratinib-associated diarrhea in female beagle dogs without the need for any loperamide administration.

Mg2+ supplementation treats secretory diarrhea in mice by activating calcium-sensing receptor in intestinal epithelial cells

Cholera is a global health problem with no targeted therapies. The Ca2+-sensing receptor (CaSR) is a regulator of intestinal ion transport and a therapeutic target for diarrhea, and Ca2+ is considered its main agonist. We found that increasing extracellular Ca2+ had a minimal effect on forskolin-induced Cl- secretion in human intestinal epithelial T84 cells. However, extracellular Mg2+, an often-neglected CaSR agonist, suppressed forskolin-induced Cl- secretion in T84 cells by 65% at physiological levels seen in stool (10 mM). The effect of Mg2+ occurred via the CaSR/Gq signaling that led to cAMP hydrolysis. Mg2+ (10 mM) also suppressed Cl- secretion induced by cholera toxin, heat-stable E. coli enterotoxin, and vasoactive intestinal peptide by 50%. In mouse intestinal closed loops, luminal Mg2+ treatment (20 mM) inhibited cholera toxin-induced fluid accumulation by 40%. In a mouse intestinal perfusion model of cholera, addition of 10 mM Mg2+ to the perfusate reversed net fluid transport from secretion to absorption. These results suggest that Mg2+ is the key CaSR activator in mouse and human intestinal epithelia at physiological levels in stool. Since stool Mg2+ concentrations in patients with cholera are essentially zero, oral Mg2+ supplementation, alone or in an oral rehydration solution, could be a potential therapy for cholera and other cyclic nucleotide-mediated secretory diarrheas.

Targeting the Epidermal Growth Factor Receptor with Molecular Degraders: State-of-the-Art and Future Opportunities

Epidermal growth factor receptor (EGFR) is an oncogenic drug target and plays a critical role in several cellular functions including cancer cell growth, survival, proliferation, differentiation, and motility. Several small-molecule tyrosine kinase inhibitors (TKIs) and monoclonal antibodies (mAbs) have been approved for targeting intracellular and extracellular domains of EGFR, respectively. However, cancer heterogeneity, mutations in the catalytic domain of EGFR, and persistent drug resistance limited their use. Different novel modalities are gaining a position in the limelight of anti-EGFR therapeutics to overcome such limitations. The current perspective reflects upon newer modalities, importantly the molecular degraders such as PROTACs, LYTACs, AUTECs, and ATTECs, etc., beginning with a snapshot of traditional and existing anti-EGFR therapies including small molecule inhibitors, mAbs, and antibody drug conjugates (ADCs). Further, a special emphasis has been made on the design, synthesis, successful applications, state-of-the-art, and emerging future opportunities of each discussed modality.

Gastrointestinal injury induced by immunomodulators: A review article

An increasing number of immunomodulators, either anti-inflammatory or immunity-enhancing, have brought about a revolutionary effect in the management of a variety of autoimmune disorders and malignancies. However, their ability to cause gastrointestinal (GI) injury and induce GI symptoms has been increasingly and unexpectedly recognized. GI injury associated with immunomodulators may demonstrate various histologic and endoscopic patterns. Optimal diagnosis and treatment require a multidisciplinary approach. This review aims to provide an overview of the literature on its pathogenesis, the clinical, endoscopic, and histologic features, and suggested approaches to manage these newly recognized immunomodulator-induced GI adverse effects (AEs). We also reviewed current biomarkers predictive of GI toxicity and potential risk factors to identify susceptible patients. In addition, these immune-mediated AEs were compared with inflammatory bowel disease, a well-documented form of inflammation-driven GI injury. We hope this review will raise awareness and vigilance among clinicians of these entities to increase early diagnosis and rapid referral to specialist care.

Safety profile of tyrosine kinase inhibitors used in non-small-cell lung cancer: An analysis from the Italian pharmacovigilance database

Introduction

Non-small cell lung cancer (NSCLC) is often caused by molecular alterations that can be detected by predictive biomarkers including mutations or amplifications of several genes. Several tyrosine kinase inhibitors (TKIs) have been approved in Europe by the European Medicines Agency (EMA) for NSCLC. The aim of this study was to analyze the onset of adverse drug reactions (ADRs) related to TKIs in NSCLC through a spontaneous reporting system (SRS) database.

Methods

All ADR reports having as suspected drug afatinib (AFT), alectinib (ALEC), brigatinib (BRG), ceritinib (CER), crizotinib (CRIZ), erlotinib (ERL), gefitinib (GEF), lorlatinib (LORL), nintedanib (NTB), and osimertinib (OSI) recorded into the Report Reazioni Avverse dei Medicinali (RAM) system database for national data and into the Italian SRS database for Sicilian data and collected from 2006 to 2021 have been evaluated. A descriptive analysis of basal demographic and drug-related characteristics was performed. A case-by-case methodology was conducted paying particular attention to all serious ADR reports collected in Sicily, focusing on type of seriousness, age, sex, concomitant drugs, and comorbidities.

Results

Of the 3,048 Italian reports, most of ADRs were related to ERL (n = 1,448), followed by AFT (n = 435) and GEF (n = 366). ADR reports were slightly more frequent in females (52.2%) and in the age group >65 years (53.0%). A higher number of cases were related to skin disorders (n = 1,766; 57.9%), followed by gastrointestinal disorders (n = 1,024; 33.6%), general disorders and administration site conditions (n = 536; 17.6%), and infections (n = 483; 15.8%). The case-by-case assessment of Sicilian ADRs showed that 33 cases were serious (12.5%) and mainly involved ERL (n = 17; 51.5%), occurring in males with a higher onset of respiratory diseases (30.3%) such as respiratory failure, interstitial lung disease and dyspnea.

Discussion

The analysis of spontaneous ADR reports of TKIs confirmed, in general, well-known risks, which often include skin, gastrointestinal, general, liver, and respiratory diseases as well as infections. However, more attention should be paid to the occurrence of serious life-threatening ADRs including respiratory failure, interstitial lung disease, and cardiogenic shock, especially in young patients.

Intestinal secretory mechanisms and diarrhea

One of the primary functions of the intestinal epithelium is to transport fluid and electrolytes to and from the luminal contents. Under normal circumstances, absorptive and secretory processes are tightly regulated such that absorption predominates, thereby enabling conservation of the large volumes of water that pass through the intestine each day. However, in conditions of secretory diarrhea, this balance becomes dysregulated, so that fluid secretion, driven primarily by Cl- secretion, overwhelms absorptive capacity, leading to increased loss of water in the stool. Secretory diarrheas are common and include those induced by pathogenic bacteria and viruses, allergens, and disruptions to bile acid homeostasis, or as a side effect of many drugs. Here, we review the cellular and molecular mechanisms by which Cl- and fluid secretion in the intestine are regulated, how these mechanisms become dysregulated in conditions of secretory diarrhea, currently available and emerging therapeutic approaches, and how new strategies to exploit intestinal secretory mechanisms are successfully being used in the treatment of constipation.

Adverse Drug Reactions with HER2-Positive Breast Cancer Treatment: An Analysis from the Italian Pharmacovigilance Database

Background

Anti-HER2 therapy has evolved in the last years and an important role in this transformation was that of monoclonal antibodies and tyrosine kinase inhibitors. Considering their extended use in clinical practice, some toxicity problems have been highlighted around these drugs.

Objective

To analyze the onset of adverse drug reactions (ADRs) related to the use of HER2-positive breast cancer treatments through a spontaneous reporting system (SRS) database.

Methods

All ADR reports having as suspected drug trastuzumab, pertuzumab, lapatinib, or trastuzumab emtansine (TDM-1), recorded into the Report Reazioni Avverse dei Medicinali (RAM) system database for national data and into the Italian SRS database for Sicilian data and collected from 2006 to 2020 have been evaluated. A descriptive analysis of basal demographic and drug-related characteristics was performed. A case-by-case methodology was conducted paying particular attention to the serious ADR reports collected in Sicily, focusing on type of seriousness, age, sex, concomitant drugs, comorbidities, time to onset (TTO), and time to resolution (TTR).

Results

Of the 3609 Italian reports, 65.6% were related to trastuzumab (n = 2367), followed by pertuzumab, TDM-1, and lapatinib. Almost all reports occurred in female patients (94.3%) and were most frequent in the age group 18–65 years (69.6%). A higher number of cases were related to general disorders and administration site conditions (n = 1079; 29.9%), gastrointestinal disorders (n = 1037; 28.7%), skin disorders (n = 821; 22.7%), and blood disorders (n = 599; 16.6%). Cases involving trastuzumab and pertuzumab mainly reported general disorders (n = 788; 33.3% and n = 194; 32.1%, respectively) while more than half of the reports associated with lapatinib were related to gastrointestinal (n = 184; 59.7%) and skin diseases (n = 146; 47.4%). Regarding TDM-1, 40% of reports had at least one ADR belonging to blood and lymphatic system disorders. The case-by-case assessment of Sicilian ADR reports showed that 40 cases were serious (33.3%), with a median TTO of 37 (6–97) days. Serious ADR reports mainly involved the onset of thrombocytopenia (n = 8; 20.0%), diarrhea (n = 6; 15.0%), asthenia and cardiac failure (both with n = 5; 12.5%), vomiting, hypersensitivity, and ejection fraction decreased (all with n = 4; 10.0%) and stomatitis (n = 3: 7.5%).

Conclusion

This study is fundamentally consistent with results from the literature. Given the serious clinical condition of breast cancer and taking into account the importance of preventing some clinically relevant ADRs related to the use of anti-HER2 therapy, further analyses are essential to better describe the safety profile of these target therapies.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40801-021-00278-z.

Calcium-activated chloride channel is involved in the onset of diarrhea triggered by EGFR tyrosine kinase inhibitor treatment in rats

EGFR tyrosine kinase inhibitors (TKIs) are mainly used to treat non-small cell lung cancer; however, adverse effects such as severe diarrhea represent a major obstacle towards the continuation of EGFR-TKIs therapy. Chloride channels, which control the fluid flow in the intestinal lumen, are proposed as an important target to remediate EGFR-TKIs-induced diarrhea, but the mechanism remains unclear. The aim of this study was to clarify the mechanism underlying EGFR-TKIs-induced diarrhea with a particular focus on the role of intestinal chloride channels. Here, we show that osimertinib-treated rats exhibit diarrhea and an increase in fecal water content without showing any severe histopathological changes. This diarrhea was attenuated by intraperitoneal treatment with the calcium-activated chloride channel (CaCC) inhibitor CaCCinh-A01. These findings were confirmed in afatinib-treated rats with diarrhea. Moreover, treatment with the Japanese traditional herbal medicine, hangeshashinto (HST), decreased fecal water content and improved fecal appearance in rats treated with EGFR-TKIs. HST inhibited the ionomycin-induced CaCC activation in HEK293 cells in patch-clamp current experiments and its active ingredients were identified. In conclusion, secretory diarrhea induced by treatment with EGFR-TKIs might be partially mediated by the activation of CaCC. Therefore, blocking the CaCC could be a potential new treatment for EGFR-TKI-induced diarrhea.

Potentiation of calcium-activated chloride secretion and barrier dysfunction may underlie EGF receptor tyrosine kinase inhibitor-induced diarrhea

Epidermal growth factor receptor tyrosine kinase inhibitors (EGFr TKIs) are first‐line therapies for various cancers, and cause dose‐limiting severe diarrhea in many patients. We hypothesized that diarrhea caused by EGFr TKIs might reflect actions on epithelial transport, barrier function, or both, which we tested using cell cultures including murine and human enteroid‐derived monolayers (EDMs), analyzed using electrophysiological and other relevant methods. EGFr TKIs (such as afatinib, erlotinib, and osimertinib) reversed the acute inhibitory effect of EGF on chloride secretion induced by carbachol (CCh) across T84 human colonic epithelial cells, which correlated with the diarrhea‐inducing effect of each agent clinically. EGFr TKIs also reduced transepithelial electrical resistance (TEER), whereas co‐treatment with CCh delayed the decrease in TEER compared with that of cells co‐treated with EGF. Furthermore, afatinib and erlotinib prevented EGF‐ or CCh‐induced EGFr phosphorylation. EGFr TKIs also suppressed phosphorylation of extracellular signal‐regulated kinase (Erk)1/2 in response to EGF, whereas they had weaker effects on CCh‐induced Erk1/2 phosphorylation. In human EDMs, EGF potentiated ion transport induced by CCh, whereas afatinib reversed this effect. The ability of EGFr TKIs to reverse the effects of EGF on calcium‐dependent chloride secretion could contribute to the diarrheal side effects of these agents, and their disruption of epithelial barrier dysfunction is likely also pathophysiologically significant. CCh‐activated Erk1/2 phosphorylation was relatively insensitive to EGFr TKIs and delayed the deleterious effects of EGFr TKIs on barrier function. These findings confirm and extend those of other authors, and may be relevant to designing strategies to overcome the diarrheal side effects of EGFr TKIs.

Epidermal growth factor receptor inhibitor-induced diarrhea: clinical incidence, toxicological mechanism, and management

The epidermal growth factor receptor (EGFR) family is a class of receptor tyrosine kinase playing a central role in carcinogenesis and cancer progression. The members of this family, particularly EGFR and human epidermal growth factor receptor 2 (HER2), are the most extensively studied drug targets for malignancy. Today, numerous tyrosine kinase inhibitors targeting EGFR family have been developed to combat non-small-cell lung cancer and breast cancer. However, severe gastrointestinal (GI) toxicity leading to dose reduction and treatment discontinuation hampers the therapeutic outcome of EGFR inhibitors. Diarrhea is one of the most frequent GI side effects, especially when it comes to second-generation EGFR inhibitors. Enterocytes apoptosis and increased inflammation accompany with many oral EGFR inhibitors. Loperamide and budesonide are the first-line treatment to manage such adverse effects. However, current prophylaxis and management are all empirical interventions to relieve the symptom. They do not specifically target the toxicological mechanism of EGFR inhibitors. Hereby, those anti-diarrhea agents do not work well when used in cancer patients experiencing EGFR inhibitor-induced diarrhea. On the other hand, the toxicological mechanism of EGFR inhibitor-induced diarrhea is poorly understood. Thus, determining the mechanism behind such diarrhea is urgently in need for developing genuinely effective anti-diarrhea agents. This review aims to call attention to EGFR inhibitor-induced diarrhea, a highly occurring and devastating cancer drug toxicity.

Visualization of Kinase Inhibition-Related Adverse Events Using the Japanese Adverse Drug Event Report Database

INTRODUCTION

Small molecule tyrosine kinase inhibitors (TKIs) inhibit not only the target kinase but also various kinases as off-target inhibitors not mentioned in the package insert. However, there are no reports that comprehensively examine the relationship between adverse events and kinase affinity.

OBJECTIVE

In this study, we combined basic data and clinical data to visualize the relationship between kinase affinity and adverse events, which will be useful for the management of adverse events in clinical practice.

METHODS

We targeted TKIs that have been used domestically and for which the dissociation constant was obtained as reported by Davis et al. Adverse event data recorded in the Japanese Adverse Drug Event Report (JADER) database provided by the Pharmaceuticals and Medical Devices Agency between April 2004 and January 2018 were used. We calculated the reporting rates of the Standardized MedDRA Queries (SMQ) for the adverse events of interest and visualized the correlation coefficients with kinase affinity. We used the adverse events associated with VEGFR2 and EGFR to assess their validity.

RESULTS

We found a correlation among known kinase-related adverse events, suggesting that the methodology may be used as a signal detection method to generate hypotheses for clinical and basic research.

CONCLUSION

Our comprehensive analysis of the kinase affinity of TKIs in this study, which was based on basic TKI kinase affinity data and the clinical data of the reporting rates, suggested that our comprehensive analysis method is useful for generating hypotheses about possible causal relationships between pharmacological effects and adverse events.

A Comprehensive Review of Contemporary Literature for Epidermal Growth Factor Receptor Tyrosine Kinase Inhibitors in Non-Small Cell Lung Cancer and Their Toxicity

Mutations in the epidermal growth factor receptor (EGFR) are common amongst those with non-small cell lung cancer and represent a major factor in treatment decisions, most notably in the advanced stages. Small molecule tyrosine kinase inhibitors (TKIs) that target the EGFR, such as erlotinib, gefitinib, icotinib, afatinib, dacomitinib and osimertinib, have all shown to be effective in this setting. Osimertinib, a third-generation EGFR TKI, is a favorable option, but almost all patients develop resistance at some time point. There are no effective treatment options for patients who progress on osimertinib, but ongoing trials will hopefully address this unmet need. The aim of this review is to provide a comprehensive review of the data with EGFR TKIs, management of the toxicities and the ongoing trials with this class of agents.

Molecular Mechanisms and Targeted Therapies Including Immunotherapy for Non-Small Cell Lung Cancer

Lung cancer is the leading cause of cancer death worldwide. Molecular targeted therapy has greatly advanced the field of treatment for non-small cell lung cancer (NSCLC), which accounts for the majority of lung cancers. Indeed, gefitinib, which was the first molecular targeted therapeutic agent, has actually doubled the survival time of NSCLC patients. Vigorous efforts of clinicians and researchers have revealed that lung cancer develops through the activating mutations of many driver genes including the epidermal growth factor receptor (EGFR), anaplastic lymphoma kinase (ALK), c-ros oncogene 1 (ROS1), v-Raf murine sarcoma viral oncogene homolog B (BRAF), and rearranged during transfection (RET) genes. Although ALK, ROS1, and RET are rare genetic abnormalities, corresponding tyrosine kinase inhibitors (TKIs) can exert dramatic therapeutic effects. In addition to anticancer drugs targeting driver genes, bevacizumab specifically binds to human vascular endothelial growth factor (VEGF) and blocks the VEGF signaling pathway. The VEGF signal blockade suppresses angiogenesis in tumor tissues and inhibits tumor growth. In this review, we also explore immunotherapy, which is a promising new NSCLC treatment approach. In general, antitumor immune responses are suppressed in cancer patients, and cancer cells escape from the immune surveillance mechanism. Immune checkpoint inhibitors (ICIs) are antibodies that target the primary escape mechanisms, immune checkpoints. Patients who respond to ICIs are reported to experience longlasting therapeutic effects. A wide range of clinical approaches, including combination therapy involving chemotherapy or radiation plus adjuvant therapy, are being developed.

Epithelial transport in digestive diseases: mice, monolayers, and mechanisms

The transport of electrolytes and fluid by the intestinal epithelium is critical in health to maintain appropriate levels of fluidity of the intestinal contents. The transport mechanisms that underlie this physiological process are also subject to derangement in various digestive disease states, such as diarrheal illnesses. This article summarizes the 2019 Hans Ussing Lecture of the Epithelial Transport Group of the American Physiological Society and discusses some pathways by which intestinal transport is dysregulated, particularly in the setting of infection with the diarrheal pathogen, Salmonella, and in patients treated with small-molecule inhibitors of the tyrosine kinase activity of the epidermal growth factor receptor (EGFr-TKI). The burdensome diarrhea in patients infected with Salmonella may be attributable to decreased expression of the chloride-bicarbonate exchanger downregulated in adenoma (DRA) that participates in electroneutral NaCl absorption. This outcome is possibly secondary to increased epithelial proliferation and/or decreased epithelial differentiation that occurs following infection. Conversely, the diarrheal side effects of cancer treatment with EGFr-TKI may be related to the known ability of EGFr-associated signaling to reduce calcium-dependent chloride secretion. Overall, the findings described may suggest targets for therapeutic intervention in a variety of diarrheal disease states.

Safety Profile of Epidermal Growth Factor Receptor Tyrosine Kinase Inhibitors: A Disproportionality Analysis of FDA Adverse Event Reporting System

Adverse event reports submitted to the US Food and Drug Administration (FDA) were analyzed to map the safety profile of epidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKIs). We conducted a disproportionality analysis of the adverse events (AEs) of EGFR-TKIs (gefitinib, erlotinib, afatinib, osimertinib) by data mining using the FDA adverse event reporting system (AERS) database, and by calculating the reporting odds ratios (ROR) with 95% confidence intervals. The FDA AERS database contained 27,123 EGFR-TKI-associated AERs within the reporting period from January 1, 2004 to March 31, 2018. Thirty-three preferred terms (PTs) were selected for analysis, and significant RORs were most commonly observed in the skin, nail, gastrointestinal tract, hepatic, eyes, and lungs. Unexpected adverse drug reactions were found in the “intestinal obstruction” and “hypokalaemia” in gefitinib and erlotinib, “hyponatraemia” in gefitinib, erlotinib and afatinib, “alopecia”in erlotinib, “hair growth abnormal” in afatinib, but not in “nausea” and “vomiting” listed on drug labels. The results of this study are consistent with clinical observation, suggesting the usefulness of pharmacovigilance research should be corroborated with the real-world FAERS data.

FDA- and EMA-Approved Tyrosine Kinase Inhibitors in Advanced EGFR-Mutated Non-Small Cell Lung Cancer: Safety, Tolerability, Plasma Concentration Monitoring, and Management

Non-small-cell lung cancer (NSCLC) is the most common form of primary lung cancer. The discovery of several oncogenic driver mutations in patients with NSCLC has allowed the development of personalized treatments based on these specific molecular alterations, in particular in the tyrosine kinase (TK) domain of the epidermal growth factor receptor (EGFR) gene. Gefitinib, erlotinib, afatinib, and osimertinib are TK inhibitors (TKIs) that specifically target EGFR and are currently approved by the Food and Drug Administration (FDA) and the European Medicines Agency (EMA) as first line treatment for sensitive EGFR-mutant patients. However, these four drugs are associated with severe adverse events (AEs) that can significantly impact patient health-related quality of life and patient monitoring. EGFR-TKIs are commonly used together with other types of medication that can substantially interact. Here, we review approaches used for the management of TKI-AEs in patients with advanced NSCLC to promote the benefits of treatments and minimize the risk of TKI treatment discontinuation. We also consider potential TKI–drug interactions and discuss the usefulness of plasma concentration monitoring TKIs based on chromatographic and mass spectrometry approaches to guide clinical decision-making. Adjusting the most appropriate therapeutic strategies and drug doses may improve the performance therapy and prognosis of patients with advanced EGFR-mutated NSCLC.

Intestinal epithelial potassium channels and CFTR chloride channels activated in ErbB tyrosine kinase inhibitor diarrhea

Diarrhea is a major side effect of ErbB receptor tyrosine kinase inhibitors (TKIs) in cancer chemotherapy. Here, we show that the primary mechanism of ErbB TKI diarrhea is activation of basolateral membrane potassium (K+) channels and apical membrane chloride (Cl-) channels in intestinal epithelia and demonstrate the efficacy of channel blockers in a rat model of TKI diarrhea. Short-circuit current in colonic epithelial cells showed that the TKIs gefitinib, lapatinib, and afatinib do not affect basal secretion but amplify carbachol-stimulated secretion by 2- to 3-fold. Mechanistic studies with the second-generation TKI afatinib showed that the amplifying effect on Cl- secretion was Ca2+ and cAMP independent, was blocked by CF transmembrane conductance regulator (CFTR) and K+ channel inhibitors, and involved EGFR binding and ERK signaling. Afatinib-amplified activation of basolateral K+ and apical Cl- channels was demonstrated by selective membrane permeabilization, ion substitution, and channel inhibitors. Rats that were administered afatinib orally at 60 mg/kg/day developed diarrhea with increased stool water from approximately 60% to greater than 80%, which was reduced by up to 75% by the K+ channel inhibitors clotrimazole or senicapoc or the CFTR inhibitor (R)-BPO-27. These results indicate a mechanism for TKI diarrhea involving K+ and Cl- channel activation and support the therapeutic efficacy of channel inhibitors.

Phase I trial of afatinib and 3-weekly trastuzumab with optimal anti-diarrheal management in patients with HER2-positive metastatic cancer

Background

Trastuzumab is the mainstay of therapy for patients with HER2-positive breast and gastric cancer but resistance frequently occurs. Afatinib, an irreversible oral ErbB family blocker, shows clinical activity in trastuzumab-refractory HER2-positive metastatic breast cancer.

Materials and methods

This phase I study used a modified 3 + 3 dose escalation design to determine the maximum tolerated dose (MTD) of oral once-daily afatinib in combination with 3-weekly intravenous trastuzumab (8 mg/kg week 1; 6 mg/kg 3-weekly thereafter) for patients with confirmed advanced or metastatic HER2-positive cancer.

Results

Of the 13 patients treated, 6 received daily afatinib 20 mg and 7 received 30 mg. One patient who received afatinib 30 mg developed a tumor lysis syndrome and was not evaluable for dose-limiting toxicity (DLT). Two of the six remaining patients receiving afatinib 30 mg and 1 of the 6 patients receiving afatinib 20 mg experienced DLTs (all CTCAE ≥ grade 2 diarrhea despite optimal management) in the first treatment cycle. The most common drug-related adverse events were diarrhea (n = 13, 100%), asthenia (n = 8, 61.5%), rash (n = 7, 53.8%) and paronychia (n = 5, 38.5%). No pharmacokinetic interaction was observed. One patient (7.7%) had an objective response (20 mg afatinib cohort). Nine patients (69.2%) experienced clinical benefit.

Conclusions

Despite optimal management of diarrhea including treatment of grade I symptoms, it was not possible to treat the patients above a dose of 20 mg of afatinib daily in combination with 3-weekly trastuzumab. The MTD of afatinib in combination with the recommended 3-weekly dose of trastuzumab was 20 mg daily.

Preventive effect of kampo medicine (hangeshashin-to, TJ-14) plus minocycline against afatinib-induced diarrhea and skin rash in patients with non-small cell lung cancer

Purpose

Diarrhea and oral mucositis induced by afatinib can cause devastating quality of life issues for patients undergoing afatinib treatment. Several studies have shown that hangeshashin-to (TJ-14) might be useful for chemotherapy-induced diarrhea and oral mucositis. In this study, we investigated the prophylactic effects of TJ-14 for afatinib-induced diarrhea and oral mucositis and minocycline for afatinib-induced skin rash.

Patients and methods

First- and second-generation epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitors have become the standard first-line treatment in patients with EGFR-mutated non-small cell lung cancer. The incidence of diarrhea was higher with afatinib than with gefitinib, and we conducted a single-arm Phase II study with afatinib. Patients who had previously undergone treatment with afatinib were ineligible. Both TJ-14 (7.5 g/day) and minocycline (100 mg/day) were administered simultaneously from the start of afatinib administration. The primary end point was the incidence of ≥ grade 3 (G3) diarrhea (increase of ≥7 stools/day over baseline) during the first 4 weeks of treatment. The secondary end points were the incidence of ≥ G3 oral mucositis (severe pain interfering with oral intake) and $ G3 skin toxicity (severe or medically significant but not immediately life-threatening).

Results

A total of 29 patients (nine men and 20 women; median age, 66 years; performance status, 0/1/2: 18/10/1) were enrolled from four centers. Four patients had undergone prior treatment with chemotherapy, including gefitinib or erlotinib. In all, 20 (68.9%) patients and one (3.4%) patient had diarrhea of any grade and ≥ G3, respectively. One (3.4%) patient had ≥ G3 oral mucositis; no patients had ≥ G3 skin rash. A total of 18 (62%) of the 29 patients achieved a partial response.

Conclusion

The present study indicated a trend in which TJ-14 reduced the risk of afatinib-induced diarrhea and minocycline reduced the risk of afatinib-induced skin rash.

Lactobacillus rhamnosus GG: An Overview to Explore the Rationale of Its Use in Cancer

Cancer is the second leading cause of death in the western world. In the era of precision medicine, a significant number of cancer patients can be cured with several anti-cancer therapeutic regimens. However, therapy failure may be caused by treatment side effects, such as diarrhea, especially occurring in patients with gastrointestinal or pelvic malignancies. In particular, diarrhea is one of the most frequent gastrointestinal toxicity during cancer treatment and it can result from nearly bot chemo- and radio-therapeutic strategies currently used. Diarrhea has a serious impact on patients’ quality of life and treatment dosing and schedule modification due to its severity can negatively influence treatment outcomes. In this context, probiotics may play an interesting role in several human diseases with an inflammatory bowel involvement and, among these, Lactobacillus rhamnosus GG (LGG) is one of the most characterized and utilized. In particular, LGG is able to reverse intestinal dysbiosis and moderate diarrhea. Moreover, preclinical studies have documented its effects in reducing chronic inflammation associated with cancer development. This review summarizes the preclinical results of LGG on cancer cells proliferation and tumor invasion as well as the potential role of LGG use in cancer patients for the prevention and management of diarrhea associated with cancer treatment. Overall, these encouraging data support further investigation on the use of LGG in stratified patients undergoing specific therapeutic protocols, including chemotherapy and pelvic radiotherapy, in order to reduce the development of severe diarrhea and thus improve the adherence to the therapy and patients’ quality of life.

The safety of afatinib for the treatment of non-small cell lung cancer

INTRODUCTION

Lung cancer tumors present EGFR mutations associated with an increased response rate to tyrosine kinase inhibitors (TKIs). Afatinib acts as an irreversible pan-ErbB-TKI. Areas covered: This review summarizes the results of clinical trials in NSCLC regarding its safety and efficacy. Expert opinion: Afatinib in 40 mg doses is highly effective in patients with NSCLC and EGFR mutations, improving progression-free survival and disease-related symptoms compared to chemotherapy. Additionally, afatinib has a better response rate and shows a small benefit in progression free survival compared to first-generation TKIs, and patients with exon 19 deletion could represent a subgroup with better prognosis and overall survival. Diarrhea, mucositis and rash are frequent adverse events induced by afatinib, these can impair quality of life and sometimes afatinib discontinuation is necessary. Management of adverse events, including early antidiarrheal treatment and prophylactic or early antibiotic management can reduce the gastrointestinal and cutaneous adverse events, respectively. Different risk factors, including malnourishment, sarcopenia, and low body surface might be associated with a higher toxicity risk, and these groups of patients could begin treatment with a low dose of afatinib followed by a close evaluation on tolerability and toxicity in order to slowly increase the dosage of afatinib.

Chenodeoxycholic acid requires activation of EGFR, EPAC, and Ca2+ to stimulate CFTR-dependent Cl- secretion in human colonic T84 cells

Bile acids are known to initiate intricate signaling events in a variety of tissues, primarily in the liver and gastrointestinal tract. Of the known bile acids, only the 7α-dihydroxy species, deoxycholic acid and chenodeoxycholic acid (CDCA), and their conjugates, activate processes that stimulate epithelial Cl^- secretion. We have previously published that CDCA acts in a rapid manner to stimulate colonic ion secretion via protein kinase A (PKA)-mediated activation of the dominant Cl^- channel, the cystic fibrosis transmembrane conductance regulator (CFTR) (Ao M, Sarathy J, Domingue J, Alrefai WA, and Rao MC. Am J Physiol Cell Physiol 305: C447-C456, 2013); however, PKA signaling did not account for the entire CDCA response. Here we show that in human colonic T84 cells, CDCA's induction of CFTR activity, measured as changes in short-circuit current (I_sc), is dependent on epidermal growth factor receptor (EGFR) activation and does not involve the bile acid receptors TGR5 or farnesoid X receptor. CDCA activation of Cl^- secretion does not require Src, mitogen-activated protein kinases, or phosphoinositide 3-kinase downstream of EGFR but does require an increase in cytosolic Ca²⁺ In addition to PKA signaling, we found that the CDCA response requires the novel involvement of the exchange protein directly activated by cAMP (EPAC). EPAC is a known hub for cAMP and Ca²⁺ cross talk. Downstream of EPAC, CDCA activates Rap2, and changes in free cytosolic Ca²⁺ were dependent on both EPAC and EGFR activation. This study establishes the complexity of CDCA signaling in the colonic epithelium and shows the contribution of EGFR, EPAC, and Ca²⁺ in CDCA-induced activation of CFTR-dependent Cl^- secretion.

Collateral Growth in the Peripheral Circulation: A Review

Arterial occlusive diseases are a major cause of morbidity and death in the United States. The enlargement of pre-existing vessels, which bypass the site of arterial occlusion, provide a natural way for the body to compensate for such obstructions. Individuals differ in their capacity to develop collateral vessels. In recent years much attention has been focused upon therapy to promote collateral development, primarily using individual growth factors. Such studies have had mixed results. Persistent controversies exist regarding the initiating stimuli, the processes involved in enlargement, the specific vessels that should be targeted, and the most appropriate terminology. Consequently, it is now recognized that more research is needed to extend our knowledge of the complex process of collateral growth. This basic science review addresses five questions essential in understanding current problems in collateral growth research and the development of therapeutic interventions.

[Toxicity associated with EGRF inhibition: review and key aspects in the management of afatinib]

Afatinib is an irreversible tyrosine kinase inhibitor of the ErbB family, approved for the treatment of patients with non-small cell lung cancer with EGFR-sensitizing mutations. Like other EGFR inhibitors, afatinib can provoke adverse events such as diarrhoea, rash, paronychia or mucositis. The correct management of these adverse events is essential to maintain quality of life in these patients and obtain the maximum benefit from afatinib therapy. This study aimed to review the toxicity of the drug and summarize recommendations for the prevention and treatment of the most significant adverse events associated with afatinib.

A systematic review and meta-analysis of the risk of diarrhea associated with vandetanib treatment in carcinoma patients

Background and purpose

Vandetanib is a promising anticancer targeted agent for treating advanced carcinomas, such as non-small-cell lung cancer, small-cell lung cancer, breast cancer, malignant glioma, hepatocellular cancer, and unresectable, locally advanced, or metastatic medullary thyroid cancer. However, diarrhea is a frequently reported adverse event. The incidence of vandetanib-associated diarrhea varies extensively in different study populations and has not been carefully estimated. This systematic review and meta-analysis of clinical trials aims to figure out the overall risks of all-grade and high-grade diarrhea during vandetanib treatment and get a better understanding of its prediction and management.

Materials and methods

A comprehensive search was performed in EMBASE, PubMed, and Cochrane Library for clinical trials studying vandetanib and diarrhea prior to April 2015. Eligible articles were selected according to the inclusion criteria. Data were extracted to calculate the summary incidence of all-grade and high-grade diarrhea caused by vandetanib treatment.

Results

Thirteen clinical trials that involved 3,264 patients were included in this meta-analysis. The overall incidences of all-grade and high-grade diarrhea caused by vandetanib treatment were 52.1% (95% confidence interval [CI], 48.3%–55.8%) and 5.6% (95% CI, 4.4%–76.7%), respectively. The risk ratios of the all-grade and high-grade diarrhea for vandetanib arm versus control arm were 1.932 (95% CI, 1.746–2.138; P<0.001) and 3.190 (95% CI, 2.061–4.938; P<0.001), respectively. Studies with small-cell lung cancer demonstrated the highest incidence of all-grade diarrhea (78.85%) and high-grade diarrhea (17.31%), whereas the lowest incidences of all-grade (42.11%) and high-grade (2.67%) diarrhea are seen in patients with hepatocellular carcinoma and non-small-cell lung cancer, respectively.

Conclusion

Our findings demonstrate that the administration of vandetanib leads to a significantly increased risk of diarrhea, which varies in different carcinoma patients. Early recognition and timely management may be key factors to avoid dose reduction, drug interruption, and drug discontinuation, which is significant to maximize the treatment benefits.

Endogenous and exogenous control of gastrointestinal epithelial function: building on the legacy of Bayliss and Starling

Transport of fluid and electrolytes in the intestine allows for appropriate adjustments in luminal fluidity while reclaiming water used in digesting and absorbing a meal, and is closely regulated. This article discusses various endogenous and exogenous mechanisms whereby transport is controlled in the gut, placing these in the context of the ideas about the neurohumoral control of alimentary physiology that were promulgated by William Bayliss and Ernest Starling. The article considers three themes. First, mechanisms that intrinsically regulate chloride secretion, centred on the epidermal growth factor receptor (EGFr), are discussed. These may be important in ensuring that excessive chloride secretion, with the accompanying loss of fluid, is not normally stimulated by intestinal distension as the meal passes through the gastrointestinal tract. Second, mechanisms whereby probiotic microorganisms can impart beneficial effects on the gut are described, with a focus on targets at the level of the epithelium. These findings imply that the commensal microbiota exert important influences on the epithelium in health and disease. Finally, mechanisms that lead to diarrhoea in patients infected with an invasive pathogen, Salmonella, are considered, based on recent studies in a novel mouse model. Diarrhoea is most likely attributable to reduced expression of absorptive transporters and may not require the influx of neutrophils that accompanies infection. Overall, the goal of the article is to highlight the many ways in which critical functions of the intestinal epithelium are regulated under physiological and pathophysiological conditions, and to suggest possible targets for new therapies for digestive disease states.

Kinase inhibitors and monoclonal antibodies in oncology: clinical implications

Molecularly targeted cancer therapies, such as small-molecule kinase inhibitors and monoclonal antibodies, constitute a rapidly growing and an important part of the oncology armamentarium. Unlike conventional (cytotoxic) chemotherapeutics, targeted therapies were designed to disrupt cancer cell pathogenesis at specific biological points essential for the development and progression of the tumour. These agents were developed to disrupt specific targets with the aim of minimizing treatment burden compared with conventional chemotherapy. Nevertheless the increasingly common use of targeted therapies has revealed some unanticipated, often clinically significant toxic effects, as well as compromising effective palliative and end-of-life management approaches. Although patients and clinicians welcome improvements in cancer prognosis, these changes can also impact patient quality-of-life. Therefore, as demand for oncology expertise increases, physicians need to apprise themselves of targeted therapies and their clinical implications, including drug-specific side effects, impact on quality of life, and cost issues, especially in relation to end-of-life care. This Review provides a useful summary and guide for professionals treating patients with malignant diseases.

Towards manageable toxicities from targeted lung cancer treatment

Targeted agents are now considered standard of care for patients whose tumors possess a sensitizing mutation in EGFR or ALK rearrangement. As the toxicity profiles of these agents differ significantly from that of cytotoxic chemotherapy, physicians need to be cognizant of the clinically relevant adverse events and manage them aggressively. Early recognition of these toxicities is vital to ensure medication compliance and maintain quality of life for patients. As more novel agents enter the treatment armamentarium, such as third-generation EGFR and ALK inhibitors, it will be important for physicians to understand class-specific toxicities and rare but serious side effects associated with these drugs.

ErbB small molecule tyrosine kinase inhibitor (TKI) induced diarrhoea: Chloride secretion as a mechanistic hypothesis

Diarrhoea is a common, debilitating and potentially life threatening toxicity of many cancer therapies. While the mechanisms of diarrhoea induced by traditional chemotherapy have been the focus of much research, the mechanism(s) of diarrhoea induced by small molecule ErbB TKI, have received relatively little attention. Given the increasing use of small molecule ErbB TKIs, identifying this mechanism is key to optimal cancer care. This paper critically reviews the literature and forms a hypothesis that diarrhoea induced by small molecule ErbB TKIs is driven by intestinal chloride secretion based on the negative regulation of chloride secretion by ErbB receptors being disrupted by tyrosine kinase inhibition.

Management of diarrhea induced by epidermal growth factor receptor tyrosine kinase inhibitors

Treatment for non-small-cell lung cancer (nsclc) is moving away from traditional chemotherapy toward personalized medicine. The reversible tyrosine kinase inhibitors (tkis) erlotinib and gefitinib were developed to target the epidermal growth factor receptor (egfr). Afatinib, an irreversible ErbB family blocker, was developed to block egfr (ErbB1), human epidermal growth factor receptor 2 (ErbB2), and ErbB4 signalling, and transphosphorylation of ErbB3. All of the foregoing agents are efficacious in treating nsclc, and their adverse event profile is different from that of chemotherapy. Two of the most common adverse events with egfr tkis are rash and diarrhea. Here, we focus on diarrhea. The key to successful management of diarrhea is to treat early and aggressively using patient education, diet, and antidiarrheal medications such as loperamide. We also present strategies for the effective assessment and management of egfr tki-induced diarrhea.

Panitumumab safety for treating colorectal cancer

INTRODUCTION

Panitumumab is a human IgG2 mAb against the EGFR, inhibiting tumor cell proliferation, survival and angiogenesis. It has demonstrated clinical efficacy in metastatic colorectal cancer (CRC) in combination with chemotherapy in first- and second-line settings and as monotherapy in third-line setting. Recently, mutations in the RAS genes have been shown to be predictive of lack of efficacy, panitumumab should be restricted to patients with RAS wild-type (wt) tumors.

AREAS COVERED

This review focuses on main efficacy results of panitumumab in metastatic CRC in first-, second- and third-line settings in combination with chemotherapy or as monotherapy. Additionally, we have covered safety aspects of this agent in these indications, especially in K-RAS and all RAS wt patients. These safety aspects refer to the most common toxicities (i.e., acne-like skin rash, diarrhea and hypomagnesaemia).

EXPERT OPINION

Panitumumab adds to the armamentarium of effective agents in the treatment of metastatic CRC. Due to its human origin, panitumumab is a well-tolerated agent with low rates of infusional reactions. Skin toxicity is frequent and should be pre-emptively treated. Other common toxicities related to panitumumab treatment, such as diarrhea and hypomagnesaemia, should be closely monitored to ensure early treatment or substitution.

Erlotinib promotes endoplasmic reticulum stress-mediated injury in the intestinal epithelium

Erlotinib, a popular drug for treating non-small cell lung cancer (NSCLC), causes diarrhea in approximately 55% of patients receiving this drug. In the present study, we found that erlotinib induced barrier dysfunction in rat small intestine epithelial cells (IEC-6) by increasing epithelial permeability and down-regulating E-cadherin. The mRNA levels of various pro-inflammatory cytokines (Il-6, Il-25 and Il-17f) were increased after erlotinib treatment in IEC-6 cells. Erlotinib concentration- and time-dependently induced apoptosis and endoplasmic reticulum (ER) stress in both IEC-6 and human colon epithelial cells (CCD 841 CoN). Intestinal epithelial injury was also observed in male C57BL/6J mice administrated with erlotinib. Knockdown of C/EBP homologous protein (CHOP) with small interference RNA partially reversed erlotinib-induced apoptosis, production of IL-6 and down-regulation of E-cadherin in cultured intestinal epithelial cells. In conclusion, erlotinib caused ER stress-mediated injury in the intestinal epithelium, contributing to its side effects of diarrhea in patients.

Drug-induced, factitious, & idiopathic diarrhoea

The aetiology of diarrhoea can often be simple to identify, but in some cases may pose a challenge. The diagnosis of drug-induced diarrhoea can easily be sorted based on timing of the symptom with onset of a new drug. Treatment can vary from simply monitoring and eventual resolution with continuation of the drug, to discontinuation of the offending agent. In cases where a drug cannot always be stopped, additional medications can help control the symptom. Factitious diarrhoea can present a diagnostic challenge if the evaluating physician does not suspect its possibility. Typically a careful history, and in some cases, stool testing can provide clues. The diagnosis of idiopathic diarrhoea is often made when exhaustive testing provides no definite aetiology and the goal of management is supportive care and symptomatic treatment.

A double-blind, randomized, multiple-dose, parallel-group study to characterize the occurrence of diarrhea following two different dosing regimens of neratinib, an irreversible pan-ErbB receptor tyrosine kinase inhibitor

PURPOSE

Neratinib, a potent, low-molecular-weight, orally administered, irreversible, pan-ErbB receptor tyrosine kinase inhibitor has antitumor activity in ErbB2 + breast cancer. The objective of this study was to characterize the onset, severity, and duration of diarrhea after administration of neratinib 240 mg once daily (QD) and 120 mg twice daily (BID) for ≤14 days in healthy subjects.

METHODS

A randomized, double-blind, parallel-group, inpatient study was conducted in 50 subjects given oral neratinib either 240 mg QD or 120 mg BID with food for ≤14 days. The primary endpoint was the proportion of subjects with diarrhea of at least moderate severity (grade 2; 5-7 loose stools/day). In subjects with grade 2 diarrhea, fecal analytes were determined. Pharmacokinetic profiles were characterized for neratinib on Days 1 and 7.

RESULTS

No severe (grade 3) diarrhea was reported. By Day 4, all subjects had grade 1 diarrhea. Grade 2 diarrhea occurred in 11/22 evaluable subjects (50 % [90 % confidence interval (CI): 28-72 %]) in the QD group and 17/23 evaluable subjects (74 % [90 % CI: 52-90 %]) in the BID group (P = 0.130). In fecal analyses, 18 % tested positive for hemoglobin and 46 % revealed fecal lactoferrin. Specimen pH was neutral to slightly alkaline. In pharmacokinetic analyses, Day 1 peak plasma concentration and Day 7 steady-state exposure were higher with the QD regimen than the BID regimen. In an exploratory analysis, ABCG2 genotype showed no correlation with severity or onset of diarrhea.

CONCLUSIONS

Incidences and onsets of at least grade 1 and at least grade 2 diarrhea were not improved on BID dosing compared with QD dosing.

Epidermal growth factor chronically upregulates Ca(2+)-dependent Cl(-) conductance and TMEM16A expression in intestinal epithelial cells

Dysregulated epithelial fluid and electrolyte transport is a common feature of many intestinal disorders. However, molecular mechanisms that regulate epithelial transport processes are still poorly understood, thereby limiting development of new therapeutics. Previously, we showed that epidermal growth factor (EGF) chronically enhances intestinal epithelial secretory function. Here, we investigated a potential role for altered expression or activity of apical Cl(−) channels in mediating the effects of EGF. Cl(−) secretion across monolayers of T(84) colonic epithelia was measured as changes in short-circuit current. Protein expression/phosphorylation was measured by RT-PCR and Western blotting. Under conditions that specifically isolate apical Ca(2+)-activated Cl(−) channel (CaCC) currents, EGF pretreatment (100 ng ml(−1) for 15 min) potentiated carbachol (CCh)-induced responses to 173 ± 25% of those in control cells, when measured 24 h later (n = 26; P < 0.01). EGF-induced increases in CaCC currents were abolished by the transmembrane protein 16A (TMEM16A) inhibitor, T16A(inh)-A01 (10 μm). Furthermore, TMEM16A mRNA and protein expression was increased by EGF to 256 ± 38% (n = 7; P < 0.01) and 297 ± 46% (n = 9, P < 0.001) of control levels, respectively. In contrast, EGF did not alter CFTR expression or activity. EGF-induced increases in Cl(−) secretion, CaCC currents and TMEM16A expression were attenuated by a PKCδ inhibitor, rottlerin (20 μm), and a phosphatidylinositol 3-kinase (PI3K) inhibitor, LY290042 (25 μm). Finally, LY290042 inhibited EGF-induced phosphorylation of PKCδ. We conclude that EGF chronically upregulates Ca(2+)-dependent Cl(−) conductances and TMEM16A expression in intestinal epithelia by a mechanism involving sequential activation of PI3K and PKCδ. Therapeutic targeting of EGF receptor-dependent signalling pathways may provide new approaches for treatment of epithelial transport disorders.

Interferon-γ alters downstream signaling originating from epidermal growth factor receptor in intestinal epithelial cells: functional consequences for ion transport

The epidermal growth factor receptor (EGFr) regulates many cellular functions, such as proliferation, apoptosis, and ion transport. Our aim was to investigate whether long term treatment with interferon-γ (IFN-γ) modulates EGF activation of downstream signaling pathways in intestinal epithelial cells and if this contributes to dysregulation of epithelial ion transport in inflammation. Polarized monolayers of T(84) and HT29/cl.19A colonocytes were preincubated with IFN-γ prior to stimulation with EGF. Basolateral potassium transport was studied in Ussing chambers. We also studied inflamed colonic mucosae from C57BL/6 mice treated with dextran sulfate sodium or mdr1a knock-out mice and controls. IFN-γ increased intestinal epithelial EGFr expression without increasing its phosphorylation. Conversely, IFN-γ caused a significant decrease in EGF-stimulated phosphorylation of specific EGFr tyrosine residues and activation of ERK but not Akt-1. In IFNγ-pretreated cells, the inhibitory effect of EGF on carbachol-stimulated K(+) channel activity was lost. In inflamed colonic tissues, EGFr expression was significantly increased, whereas ERK phosphorylation was reduced. Thus, although it up-regulates EGFr expression, IFN-γ causes defective EGFr activation in colonic epithelial cells via reduced phosphorylation of specific EGFr tyrosine residues. This probably accounts for altered downstream signaling consequences. These observations were corroborated in the setting of colitis. IFN-γ also abrogates the ability of EGF to inhibit carbachol-stimulated basolateral K(+) currents. Our data suggest that, in the setting of inflammation, the biological effect of EGF, including the inhibitory effect of EGF on Ca(2+)-dependent ion transport, is altered, perhaps contributing to diarrheal and other symptoms in vivo.

Epidermal growth factor upregulates serotonin transporter in human intestinal epithelial cells via transcriptional mechanisms

Serotonin transporter (SERT) regulates extracellular availability of serotonin and is a potential pharmacological target for gastrointestinal disorders. A decrease in SERT has been implicated in intestinal inflammatory and diarrheal disorders. However, little is known regarding regulation of SERT in the intestine. Epidermal growth factor (EGF) is known to influence intestinal electrolyte and nutrient transport processes and has protective effects on intestinal mucosa. Whether EGF regulates SERT in the human intestine is not known. The present studies examined the regulation of SERT by EGF, utilizing Caco-2 cells grown on Transwell inserts as an in vitro model. Treatment with EGF from the basolateral side (10 ng/ml, 24 h) significantly stimulated SERT activity (∼2-fold, P < 0.01) and mRNA levels compared with control. EGF increased the activities of the two alternate promoter constructs for human SERT gene: SERT promoter 1 (hSERTp1, upstream of exon 1a) and SERT promoter 2 (hSERTp2, upstream of exon 2). Inhibition of EGF receptor (EGFR) tyrosine kinase activity by PD168393 (1 nM) blocked the stimulatory effects of EGF on SERT promoters. Progressive deletions of the SERT promoter indicated that the putative EGF-responsive elements are present in the -672/-472 region of the hSERTp1 and regions spanning -1195/-738 and -152/+123 of hSERTp2. EGF markedly increased the binding of Caco-2 nuclear proteins to the potential AP-1 cis-elements present in EGF-responsive regions of hSERTp1 and p2. Overexpression of c-jun but not c-fos specifically transactivated hSERTp2, with no effects on hSERTp1. Our findings define novel mechanisms of transcriptional regulation of SERT by EGF via EGFR at the promoter level that may contribute to the beneficial effects of EGF in gut disorders.

[Management of side-effects of targeted therapies in renal cancer: gastrointestinal side-effects]

Several types of gastrointestinal complications can occur during treatment with targeted therapies: diarrhoea, nausea and vomiting, abnormalities in hepatic and pancreatic profiles, etc. Gastrointestinal problems in targeted therapy can have a significant impact on the general status of patients, their weight and their adherence to the treatment. The prevention, screening and rapid treatment of these side-effects are essential elements of patient care and can limit the associated dose reductions and loss of therapeutic benefit. In the case of diarrhoea, treatment must be started at the onset of grade 1 or 2 diarrhoea (four to six stools per day), with loperamide or racecadotril. Treatment with targeted therapy must be stopped if there is diarrhoea of grade 3 or 4 (more than six stools per day). In the case of nausea/vomiting or burning pain in the oesophagus, symptomatic treatment without stopping the targeted therapy is recommended. Biological assessment including transaminases, total and conjugated bilirubin should be prescribed before treatment initiation with targeted therapy. An elevation in alkaline phosphatases without elevation of transaminases suggests primarily the existence of hepatic metastases. In the event of worsening of the hepatic profile, if ALT greater than 5N, treatment must be stopped and specialist advice sought.

Loss of protein tyrosine phosphatase N2 potentiates epidermal growth factor suppression of intestinal epithelial chloride secretion

The Crohn's disease candidate gene, protein tyrosine phosphatase nonreceptor type 2 (PTPN2), has been shown to regulate epidermal growth factor (EGF)-induced phosphatidylinositol 3-kinase (PI3K) activation in fibroblasts. In intestinal epithelial cells (IECs), EGF-induced EGF receptor (EGFR) activation and recruitment of PI3K play a key role in regulating many cellular functions including Ca(2+)-dependent Cl(-) secretion. Moreover, EGFR also serves as a conduit for signaling by other non-growth factor receptor ligands such as the proinflammatory cytokine, IFN-γ. Here we investigated a possible role for PTPN2 in the regulation of EGFR signaling and Ca(2+)-dependent Cl(-) secretion in IECs. PTPN2 knockdown enhanced EGF-induced EGFR tyrosine phosphorylation in T(84) cells. In particular, PTPN2 knockdown promoted EGF-induced phosphorylation of EGFR residues Tyr-992 and Tyr-1068 and led subsequently to increased association of the catalytic PI3K subunit, p110, with EGFR and elevated phosphorylation of the downstream marker, Akt. As a functional consequence, loss of PTPN2 potentiated EGF-induced inhibition of carbachol-stimulated Ca(2+)-dependent Cl(-) secretion. In contrast, PTPN2 knockdown affected neither IFN-γ-induced EGFR transactivation nor EGF- or IFN-γ-induced phosphorylation of ERK1/2. In summary, our data establish a role for PTPN2 in the regulation of EGFR signaling in IECs in response to EGF but not IFN-γ. Knockdown of PTPN2 directs EGFR signaling toward increased PI3K activation and increased suppression of epithelial chloride secretory responses. Moreover, our findings suggest that PTPN2 dysfunction in IECs leads to altered control of intestinal epithelial functions regulated by EGFR.

Association of polymorphisms in AKT1 and EGFR with clinical outcome and toxicity in non-small cell lung cancer patients treated with gefitinib

EGFR mutations are strongly predictive of epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitor activity in non-small cell lung cancer (NSCLC), but resistance mechanisms are not completely understood. The interindividual variability in toxicity also points out to the need of novel pharmacogenetic markers to select patients before therapy. Therefore, we evaluated the associations between EGFR and AKT1 polymorphisms and outcome/toxicity in gefitinib-treated NSCLC patients. Polymorphic loci in EGFR, and AKT1, and EGFR and K-Ras mutations were assessed in DNA isolated from blood samples and/or paraffin-embedded tumor from 96 gefitinib-treated NSCLC patients. Univariate and multivariate analyses compared genetic variants with clinical efficacy and toxicity using Fisher's, log-rank test, and Cox's proportional hazards model. AKT1-SNP4 association with survival was also evaluated in 127 chemotherapy-treated/gefitinib-naive patients, whereas its relationship with AKT1 expression and gefitinib cytotoxicity was studied in 15 NSCLC cell lines. AKT1-SNP4 A/A genotype was associated with shorter time-to-progression (P = 0.04) and overall survival (P = 0.007). Multivariate analyses and comparison with the gefitinib-nontreated population underlined its predictive significance, whereas the in vitro studies showed the association of lower AKT1 mRNA levels with gefitinib resistance. In contrast, EGFR-activating mutations were significantly correlated with response, longer time-to-progression, and overall survival, whereas EGFR -191C/A (P < 0.001), -216 G/T (P < 0.01), and R497K (P = 0.02) polymorphisms were strongly associated with grade >1 diarrhea. AKT1-SNP4 A/A genotype seems to be a candidate biomarker of primary resistance, whereas EGFR -191C/A, -216G/T, and R497K polymorphisms are associated with diarrhea when using gefitinib in NSCLC patients, thus offering potential new tools for treatment optimization.

Genomic, tissue expression, and protein characterization of pCLCA1, a putative modulator of cystic fibrosis in the pig

Recent studies have identified members of the CLCA (chloride channels, calcium-activated) gene family as potential modulators of the cystic fibrosis (CF) phenotype, but differences between the human and murine CLCA genes and proteins may limit the use of murine CF models. Recently established pig models of CF are expected to mimic the human disease more closely than the available mouse models do. Here, we characterized the porcine CLCA gene locus, analyzed the expression pattern and protein processing of pCLCA1, and compared it to its human ortholog, hCLCA1. The porcine CLCA gene family is located on chromosome 4q25, with a broad synteny with the human and murine clca gene loci, except for a pig-specific gene duplication of pCLCA4. Using pCLCA1-specific antibodies, the protein was immunohistochemically localized in mucin-producing cells, including goblet cells and mucinous glands in the respiratory and alimentary tracts. Similar to hCLCA1, biochemical characterization of pCLCA1 identified a secreted soluble protein that could serve as an extracellular signaling molecule or functional constituent of the protective mucous layers. The results suggest that pCLCA1 shares essential characteristics of hCLCA1, supporting the pig model as a promising tool for studying the modulating role of pCLCA1 in the complex pathology of CF.

Regulation of intestinal electroneutral sodium absorption and the brush border Na+/H+ exchanger by intracellular calcium

The intestinal electroneutral Na(+) absorptive processes account for most small intestinal Na(+) absorption in the period between meals and also for the great majority of the increase in ileal Na(+) absorption that occurs postprandially. In most diarrheal diseases, there is inhibition of neutral NaCl absorption. Elevated levels of intracellular calcium ([Ca(2+)](i)) are known to inhibit NaCl absorption and involve multiple components of the Ca(2+) signaling pathway. The BB Na(+)/H(+) exchanger NHE3 accounts for most of the recognized digestive changes in neutral NaCl absorption, as well as most of the changes in Na(+) absorption that occur in diarrheal diseases. Previous studies have examined several aspects of Ca(2+) regulation of NHE3 activity. These include phosphorylation, protein trafficking, and multiprotein complex formation. In addition, recent studies have demonstrated the role of the NHERF family of PDZ domain-containing proteins in Ca(2+) regulation of NHE3 activity, thereby adding a new level of complexity to understanding Ca(2+)-dependent inhibition of Na(+) absorption. In this article, we will review the current understanding of (1) Ca(2+) signaling events in intestinal epithelial cells; (2) Ca(2+) regulation of intestinal electroneutral sodium absorption, which includes NHE3; and (3) the role of the NHERF family of PDZ domain-containing proteins in Ca(2+) regulation of NHE3 activity. We will also present new data on using advanced imaging showing rapid BB NHE3 endocytosis in response to elevated [Ca(2+)](i).

Clinical Efficacy and Toxicity of Anti-EGFR Therapy in Common Cancers

Epidermal growth factor receptor (EGFR) is a cell surface molecule and member of the ErbB family of receptor tyrosine kinases. Its activation leads to proliferation, antiapoptosis, and metastatic spread, making inhibition of this pathway a compelling target. In recent years, an increasing number of clinical trials in the management of solid malignancies have become available indicating the clinical efficacy of anti-EGFR monoclonal antibodies and oral small molecule tyrosine kinase inhibitors (TKIs). This review addresses frequently used EGFR inhibitors, summarizes clinical efficacy data of these new therapeutic agents, and discusses their associated toxicity and management.

Decoding epithelial signals: critical role for the epidermal growth factor receptor in controlling intestinal transport function

The intestinal epithelium engages in bidirectional transport of fluid and electrolytes to subserve the physiological processes of nutrient digestion and absorption, as well as the elimination of wastes, without excessive losses of bodily fluids that would lead to dehydration. The overall processes of intestinal ion transport, which in turn drive the secretion or absorption of water, are accordingly carefully regulated. We and others have identified the epidermal growth factor receptor (EGFr) as a critical regulator of mammalian intestinal ion transport. In this article, we focus on our studies that have uncovered the intricate signalling mechanisms downstream of EGFr that regulate both chloride secretion and sodium absorption by colonocytes. Emphasis will be placed on the EGFr-associated regulatory pathways that dictate the precise outcome to receptor activation in response to signals that may seem, on their face, to be quite similar if not identical. The concepts to be discussed underlie the ability of the intestinal epithelium to utilize a limited set of signalling effectors to produce a variety of outcomes suitable for varying physiological and pathophysiological demands. Our findings therefore are relevant not only to basic biological principles, but also may ultimately point to new therapeutic targets in intestinal diseases where ion transport is abnormal.