Detection of cytokeratins 19/20 and guanylyl cyclase C in peripheral blood of colorectal cancer patients

The clinical significance of detecting supposed tumour cell-derived mRNA transcripts in blood using the polymerase chain reaction (PCR) remains unclear. We have used a fully quantitative 5′-nuclease RT-PCR assay to screen for the expression of cytokeratins (ck) 19 and 20 and guanylyl cyclase C (GCC) in the peripheral blood of 21 healthy controls and 27 colorectal cancer patients. Expression of cytokeratin 19 and 20 mRNA was detected in 30% and 100% of samples, respectively, taken from healthy volunteers. There was no apparent difference in ck19 and ck20 mRNA transcription levels between controls and patients, or between patients with different Dukes' stages. While GCC mRNA was detected in only 1/21 control samples, it was expressed in approximately 80% of patients, although again there was no correlation between GCC levels and disease stage. Transcription levels of all three markers varied considerably between samples, even between samples taken from the same person at different times. We conclude that neither ck19 nor ck20 are reliable markers for the detection of colon epithelial cells in peripheral blood and that an evaluation of the usefulness of GCC awaits further longitudinal studies. © 1999 Cancer Research Campaig

Loss of Guanylyl Cyclase C (GCC) Signaling Leads to Dysfunctional Intestinal Barrier

Guanylyl Cyclase C (GCC) signaling via uroguanylin (UGN) and guanylin activation is a critical mediator of intestinal fluid homeostasis, intestinal cell proliferation/apoptosis, and tumorigenesis. As a mechanism for some of these effects, we hypothesized that GCC signaling mediates regulation of intestinal barrier function.Paracellular permeability of intestinal segments was assessed in wild type (WT) and GCC deficient (GCC-/-) mice with and without lipopolysaccharide (LPS) challenge, as well as in UGN deficient (UGN-/-) mice. IFNγ and myosin light chain kinase (MLCK) levels were determined by real time PCR. Expression of tight junction proteins (TJPs), phosphorylation of myosin II regulatory light chain (MLC), and STAT1 activation were examined in intestinal epithelial cells (IECs) and intestinal mucosa. The permeability of Caco-2 and HT-29 IEC monolayers, grown on Transwell filters was determined in the absence and presence of GCC RNA interference (RNAi). We found that intestinal permeability was increased in GCC-/- and UGN-/- mice compared to WT, accompanied by increased IFNγ levels, MLCK and STAT1 activation in IECs. LPS challenge promotes greater IFNγ and STAT1 activation in IECs of GCC-/- mice compared to WT mice. Claudin-2 and JAM-A expression were reduced in GCC deficient intestine; the level of phosphorylated MLC in IECs was significantly increased in GCC-/- and UGN-/- mice compared to WT. GCC knockdown induced MLC phosphorylation, increased permeability in IEC monolayers under basal conditions, and enhanced TNFα and IFNγ-induced monolayer hyperpermeability.GCC signaling plays a protective role in the integrity of the intestinal mucosal barrier by regulating MLCK activation and TJ disassembly. GCC signaling activation may therefore represent a novel mechanism in maintaining the small bowel barrier in response to injury

A monomethyl auristatin E-conjugated antibody to guanylyl cyclase C is cytotoxic to target-expressing cells <i>in vitro</i> and <i>in vivo</i>

<div><p>Guanylyl cyclase C (GCC) is a cell-surface protein that is expressed by normal intestinal epithelial cells, more than 95% of metastatic colorectal cancers (mCRC), and the majority of gastric and pancreatic cancers. Due to strict apical localization, systemically delivered GCC-targeting agents should not reach GCC in normal intestinal tissue, while accessing antigen in tumor. We generated an investigational antibody-drug conjugate (TAK-264, formerly MLN0264) comprising a fully human anti-GCC monoclonal antibody conjugated to monomethyl auristatin E via a protease-cleavable peptide linker. TAK-264 specifically bound, was internalized by, and killed GCC-expressing cells <i>in vitro</i> in an antigen-density-dependent manner. In GCC-expressing xenograft models with similar GCC expression levels/patterns observed in human mCRC samples, TAK-264 induced cell death, leading to tumor regressions and long-term tumor growth inhibition. TAK-264 antitumor activity was generally antigen-density-dependent, although some GCC-expressing tumors were refractory to TAK-264-targeted high local concentrations of payload. These data support further evaluation of TAK-264 in the treatment of GCC-expressing tumors.</p></div

Phase II study of the antibody-drug conjugate TAK-264 (MLN0264) in patients with metastatic or recurrent adenocarcinoma of the stomach or gastroesophageal junction expressing guanylyl cyclase C

Background The first-in-class antibody–drug conjugate TAK-264 (formerly MLN0264) consists of an antibody targeting guanylyl cyclase C (GCC) conjugated to monomethyl auristatin E (MMAE) via a peptide linker. This phase II study evaluated the efficacy and safety of TAK-264 in patients with adenocarcinoma of the stomach or gastroesophageal junction expressing GCC, who had progressed on ≥1 line of prior therapy. Methods This study used a two-stage design, with an interim analysis conducted after stage I to determine whether to continue to stage II or discontinue on the grounds of futility. Adult patients with gastric and gastroesophageal junction adenocarcinoma expressing low, intermediate, or high GCC levels received TAK-264 1.8 mg/kg as a 30-min intravenous infusion once every 21 days, for up to 1 year. The primary endpoint was objective response rate. Radiographic assessments of tumor burden were performed every 2 cycles (6 weeks). Results A total of 38 patients participated in the study. Patients received a median of 2 (range 1–14) cycles; 8 (21%) received at least 6 cycles. The most common adverse events were nausea (53%), fatigue (32%), and decreased appetite (29%). Grade ≥3 events including anemia, diarrhea, and neutropenia were seen in 14 (37%) patients. Systemic exposure to TAK-264 was maintained throughout each treatment cycle. Two patients (6%) with intermediate GCC expression had objective responses. Conclusions TAK-264 demonstrated a manageable safety profile in this patient population. The stage I interim analysis did not support continuation to stage II of the study.SCOPUS: ar.jinfo:eu-repo/semantics/publishe