Randomized open-label controlled study of cancer vaccine OSE2101 versus chemotherapy in HLA-A2-positive patients with advanced non-small-cell lung cancer with resistance to immunotherapy: ATALANTE-1

BACKGROUND

Patients with advanced non-small-cell lung cancer (NSCLC) treated with immune checkpoint blockers (ICBs) ultimately progress either rapidly (primary resistance) or after durable benefit (secondary resistance). The cancer vaccine OSE2101 may invigorate antitumor-specific immune responses after ICB failure. The objective of ATALANTE-1 was to evaluate its efficacy and safety in these patients.

PATIENTS AND METHODS

ATALANTE-1 was a two-step open-label study to evaluate the efficacy and safety of OSE2101 compared to standard-of-care (SoC) chemotherapy (CT). Patients with human leukocyte antigen (HLA)-A2-positive advanced NSCLC without actionable alterations, failing sequential or concurrent CT and ICB were randomized (2 : 1) to OSE2101 or SoC (docetaxel or pemetrexed). Primary endpoint was overall survival (OS). Interim OS futility analysis was planned as per Fleming design. In April 2020 at the time of interim analysis, a decision was taken to prematurely stop the accrual due to coronavirus disease 2019 (COVID-19). Final analysis was carried out in all patients and in the subgroup of patients with ICB secondary resistance defined as failure after ICB monotherapy second line ≥12 weeks.

RESULTS

Two hundred and nineteen patients were randomized (139 OSE2101, 80 SoC); 118 had secondary resistance to sequential ICB. Overall, median OS non-significantly favored OSE2101 over SoC {hazard ratio (HR) [95% confidence interval (CI)] 0.86 [0.62-1.19], P = 0.36}. In the secondary resistance subgroup, OSE2101 significantly improved median OS versus SoC [11.1 versus 7.5 months; HR (95% CI) 0.59 (0.38-0.91), P = 0.017], and significantly improved post-progression survival (HR 0.46, P = 0.004), time to Eastern Cooperative Oncology Group (ECOG) performance status deterioration (HR 0.43, P = 0.006) and Quality of Life Questionnaire Core 30 (QLQ-C30) global health status compared to SoC (P = 0.045). Six-month disease control rates and progression-free survival were similar between groups. Grade ≥3 adverse effects occurred in 11.4% of patients with OSE2101 and 35.1% in SoC (P = 0.002).

CONCLUSIONS

In HLA-A2-positive patients with advanced NSCLC and secondary resistance to immunotherapy, OSE2101 increased survival with better safety compared to CT. Further evaluation in this population is warranted.

Lorlatinib for advanced ROS1+ non-small-cell lung cancer: results of the IFCT-1803 LORLATU study

Introduction

ROS1-rearranged (ROS1+) non-small-cell lung cancer (NSCLC) is a rare lung cancer with limited treatment options. Phase I-II studies with ROS1-tyrosine kinase inhibitors (TKIs) included small numbers of patients and real-world data are lacking. We investigate the efficacy and safety of lorlatinib, a third-generation TKI targeting ALK and ROS1, in patients with ROS1+ NSCLC treated through an expanded access program.

Methods

Consecutive patients with advanced ROS1+ NSCLC treated with lorlatinib between October 2015 and June 2019 were included. Data were collected from medical records. The primary endpoint was progression-free survival.

Results

Out of the 80 patients included, 47(59%) were female, 49(62%) never smokers (less than 100 cigarettes over the lifetime), and 68(85%) had stage IV NSCLC at diagnosis. Most frequent histology was adenocarcinoma (95%) and median age was 58.2 years. At the time of lorlatinib initiation, 51(64%) patients had brain metastases and 55(81%) were PS 0-1. Lorlatinib was administered as second/third/fourth/fifth+ line in 29%/28%/18%/26% of patients. All patients previously received at least one ROS1 TKI, and 55(69%) previously received chemotherapy. Median follow-up from lorlatinib initiation was 22.2 months. Median progression-free survival and overall survival from lorlatinib initiation were 7.1 months [95% confidence interval (CI) 5.0-9.9 months] and 19.6 months (95% CI 12.3-27.5 months). Median duration of treatment with lorlatinib was 7.4 months (95% CI 6.5-13.1 months). Overall response and disease control rates were 45% and 82%, respectively. The central nervous system response rate was 72%. Treatment was stopped due to toxicity in 10 patients (13%). The safety profile was consistent with previously published data.

Conclusions

Lorlatinib is a major treatment option for advanced refractory ROS1+ NSCLC in treatment strategy.

•

Data are lacking on lorlatinib efficacy in advanced refractory ROS1+ NSCLC.

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Lorlatinib median progression-free survival and objective response rate were 7.1 months and 45%, respectively.

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Lorlatinib represents a major treatment option for patients with a ROS1+ NSCLC.

Cachexia - sarcopenia as a determinant of disease control rate and survival in non-small lung cancer patients receiving immune-checkpoint inhibitors

PURPOSE

The metabolic changes associated with cachexia - sarcopenia syndrome might down-regulate antitumor immunity. We hypothesized that this syndrome reduces efficiency of immune checkpoint inhibitors (ICPI) in non-small cell lung cancer (NSCLC).

METHODS

The records of 142 consecutive NSCLC patients receiving first- or second-line anti-Programmed cell death protein 1) ICPI were reviewed. Response evaluation according to Response Evaluation Criteria in Solid Tumors 1.1 was performed at the eighth week of immunotherapy. Pretreatment cachexia was defined as a body-weight loss of 5% or more in the previous 6 months. Sarcopenia was estimated with the third lumbar skeletal muscle mass index (mSMI) and was evaluated before immunotherapy and at the eighth week. A decrease by 5% or more of the mSMI was considered as an evolving sarcopenia. The endpoints were disease control rate (DCR), progression-free (PFS) and overall survival (OS).Logistic regression model and Cox model took into account others covariables known to influence ICPI efficiency, particularly Programmed Death -Ligand 1 tumor cell score, Eastern Cooperative Oncology Group performance status and common somatic mutational status.

RESULTS

In multivariate analysis, cachexia - sarcopenia syndrome reduced the probability of achieving a disease control and were associated with a shorter survival. Patients without cachexia had a better probability to achieve disease control in comparison with those who did not experience cachexia (59.9 % and 41.1 %, respectively; odds ratio 95 % (confidence interval [95 %CI]): 2.60 (1.03-6.58)). Patients with cachexia had a shorter OS when compared with those without cachexia (hazard ratios [HR] (95 %CI): 6.26 (2.23-17.57)). Patients with an evolving sarcopenia had a shorter PFS and OS, with HR (95 %CI): 2.45 (1.09-5.53) and 3.87 (1.60-9.34) respectively.

CONCLUSION

Cachexia - sarcopenia syndrome negatively influences patients' outcome during anti-PD-1 ICPI therapy.

Development and Validation of a Simplified Prognostic Score in SCLC

Introduction

This study aimed at generating a new simplified prognostic score (SPS) using common clinical and biological variables to discriminate a limited number of subgroups of patients with SCLC differing by their overall survival (OS).

Methods

The SPS was developed exploring the Montpellier University Hospital retrospective database of 401 patients over a 16-year period. All patients had received etoposide - platinum-based chemotherapy as first-line treatment. The SPS development took into account significant determinants of OS in the Cox model, weighted by their regression β coefficients. Validation of the consequent SPS has been done separately in a combined population of 213 patients accrued from two different published trials (NCT03059667 and NCT00930891).

Results

The significant independent determinants of OS included the following: (1) American Joint Committee on Cancer TNM stage IV (hazard ratio [HR]: 2.52; 95% confidence interval [CI]: 1.91–3.33); (2) Eastern Cooperative Oncology Group performance status greater than 1 (HR: 2.27; 95% CI: 1.79–2.87); (3) the presence of liver metastases (HR: 1.66; 95% CI: 1.29–2.15); and (4) neutrophil-to-lymphocyte ratio greater than 4 (HR: 1.39; 95% CI: 1.11–1.92). The SPS generated with these four variables, segregated three groups (good, intermediate, and poor prognosis) with respective median OS of 26.9 months (95% CI: 20.1–38.9), 11.5 months (95% CI: 9.8–13.0), and 6.8 months (95% CI: 5.8–8.3; log-rank p < 10^–4). Harrell's C statistic estimate was 0.68 ± 0.012, suggesting goodness of calibration. In the validation cohort, the SPS segregated the aforementioned three subgroups in a nearly similar manner, with respective median OS: 27.2, 12.3, and 8.6 months (log-rank p < 10^–3; Harrell’s C statistic: 0.58 ± 0.02).

Conclusions

The SPS is easy to calculate in real-life practice and efficiently discriminates three populations with different prognoses. This study deserves further validation of this score in patients with SCLC receiving immunochemotherapy.

Synchronous multiple non-small cell lung cancers in an allograft lung recipient

We described a case report of synchronous non-small cell lung cancers arising in lung transplants after allograft. Immunosuppressive therapy of the recipient induced an accelerated growth rate of primary tumour and metastases as was been observed in orthotopic liver allograft for hepatocellular carcinoma.

[What do chemotherapy specialists expect of lung cancer?]

OBJECTIVE

In an attempt to understand physicians' expectations of chemotherapy, a group of lung cancer specialists was involved in an online survey investigating their opinions by a self-questionnaire. The questionnaire described five different chemotherapy prescription situations for lung cancer patients (stages IIIB or IV).

METHOD

A total of 30 expert specialists were invited; 22 responded (73%). For each of the clinical situations, the expert was asked for his opinion on 3 items: cure, prolongation of survival and alleviation of symptoms. Each item was judged on a Likert scale with categories between -2 "not at all probable" and +2 "quite likely".

RESULTS

For "cure", the percentage of -2 responses differed significantly according to the clinical situation (Fisher test: P<0.00001). The trend test showed a relationship between the percentage of -2 responses and the suspected order of the clinical situations (Cochran-Armitage trend test: P<0.0001). For symptom alleviation, the percentage of responses +2 and +1 differed significantly according to the clinical situation (Fisher test: P=0.00013, trend test: P<0.0001).

CONCLUSION

What specialist physicians expect of chemotherapy in terms of curability and symptom relief differs according to the actual statistical prognosis of each situation as presented in the literature. The worst prognostic situation leads to the strongest expectation in terms of symptom relief and, conversely, the lowest for curability.

Qualitative study of patients' decision-making when accepting second-line treatment after failure of first-line chemotherapy

Objective

Treatment failures in advanced lung cancer are frequent events affecting patients during or after first-line chemotherapy. International guidelines recommend second-line chemotherapy. However, around one half of patients who experience disease progression enter a systemic second-line therapy. In the herein qualitative study, we investigated patients' thoughts and attitudes determining the decision to undergo a second-line chemotherapy.

Methods

Thirty-three purposively selected patients who recently accepted second-line or palliative chemotherapy were invited to participate in this survey consisting of semi-structured in-depth interviews. Grounded theory was applied to investigate participants’ perceptions of the context that have surrounded their decision to undergo palliative chemotherapy.

Results

For most patients, tumor burden and reduced quality of life in relation with lung cancer itself were major drivers of the decision-making process. There was a balance between two different attitudes: making a decision to undergo a new line of chemotherapy or starting a psychological process in order to accept end of life. Choosing between these two attitudes allowed the patient to keep the matter of palliative care at a distance. Even in case of low chance of success, many patients who worried about their life partner's future would accept a new chemotherapy line. Some patients experienced ambivalent thoughts regarding social network, particularly about their family as daily function impairment required an increased need for relative's support. The initial "Worrying about others" thoughts left place to in an increasing self-need of care as those provided by relatives; this phenomenon might increase patients' self- perception of being a burden for others. Confidence previously established with formal caregiver support was another major decision driver: some patients with sustained confidence in their medical staff may have privileged this formal support rather than family support when the latter was perceived as weak, insufficient or intrusive.

Conclusion

This study identified three domains involved into a complex interplay for lung cancer patients’ decision regarding second-line palliative chemotherapy: (i) perception of the definitive loss of health, (ii) interactions between idiosyncrasy (hope, disease burden) and environment (healthcare and social network support), and (iii) patient's subjective evaluation of chemotherapy benefit–risk.

Morbidity and mortality in the antiphospholipid syndrome during a 5-year period: a multicentre prospective study of 1000 patients

Objectives:

To identify the main causes of morbidity and mortality in patients with antiphospholipid syndrome (APS) during a 5-year period and to determine clinical and immunological parameters with prognostic significance.

Methods:

The clinical and immunological features of a cohort of 1000 patients with APS from 13 European countries who had been followed up from 1999 to 2004 were analysed.

Results:

200 (20%) patients developed APS-related manifestations during the 5-year study period. Recurrent thrombotic events appeared in 166 (16.6%) patients and the most common were strokes (2.4% of the total cohort), transient ischaemic attacks (2.3%), deep vein thromboses (2.1%) and pulmonary embolism (2.1%). When the thrombotic events occurred, 90 patients were receiving oral anticoagulants and 49 were using aspirin. 31/420 (7.4%) patients receiving oral anticoagulants presented with haemorrhage. 3/121 (2.5%) women with only obstetric APS manifestations at the start of the study developed a new thrombotic event. A total of 77 women (9.4% of the female patients) had one or more pregnancies and 63 (81.8% of pregnant patients) had one or more live births. The most common fetal complications were early pregnancy loss (17.1% of pregnancies) and premature birth (35% of live births). 53 (5.3% of the total cohort) patients died. The most common causes of death were bacterial infection (21% of deaths), myocardial infarction (19%) and stroke (13%). No clinical or immunological predictor of thrombotic events, pregnancy morbidity or mortality was detected.

Conclusion:

Patients with APS still develop significant morbidity and mortality despite current treatment (oral anticoagulants or antiaggregants, or both).

Hyperurikämie und Gicht

In our modern society hyperuricemia is one of the most frequent metabolism disturbances. So far, every fourth man and every tenth woman suffer from an asymptomatic or a symptomatic hyperuricemia named gout. Mostly, over nutrition and malnutrition as well as other secondary factors with a genetically determined renal secretion disturbance of uric acid lead to an increase of serum uric acid. By deposition of uric acid crystals in tissues with intermittent immunologic activation of inflammation cells a manifestation of gout can be seen. The clinical image of gout varies widely. It may manifest as acute or chronic arthritis, tophi on the skin, subcutaneous tissue and the skeletal system as well as urate nephropathy. To eliminate the consequences of hyperuricemia in the long term, apart from a thorough anamnesis of nutritional habits a general examination of metabolic parameters is necessary to exclude a metabolic syndrome and other causes for a secondarily caused hyperuricemia. As gout is very often primarily caused by a renal secretion disturbance of uric acid special diagnostics should be done. Basing on literature research and inclusion of experts opinions this article represents the therapeutically options in treatment of hyperuricemia and gout with their resulting side effects and contraindications.

Oxidativ modifizierte Lipoproteine und deren Antik�rper bei Patienten mit Antiphospholipidsyndrom und Systemischem Lupus erythematodes

The antiphospholipid syndrome (APS) with its typical clinical manifestations of recurrent thrombosis and fetal loss is biochemically defined by the presence of circulating antiphospholipid antibodies (aPL). The disease pattern has raised special interest as a possible link between autoimmunity and atherosclerosis. aPL, oxidized low density lipoproteins (oxLDL), and antibodies to oxLDL (Anti-oxLDL) are suggested to play an important role in atherogenesis. In the present study we compared the serum levels of oxLDL and Anti-oxLDL in APS patients (20 subjects with primary APS; 14 subjects with secondary APS) and nonAPS subjects (24 phenotypically healthy controls samples and 12 patients with systemic lupus erythematosus [SLE]) and investigated associations of the above mentioned parameters with the intima-media thickness (IMT), a clinical surrogate parameter of atherosclerosis.SLE patients with and without APS showed significantly increased levels of Anti-oxLDL as compared to the controls group (p = 0.038 and p = 0.007, respectively). In contrast, oxLDL levels were not significantly different between the controls group and patients. The Anti-oxLDL levels correlated significantly with anticardiolipin (p = 0.002) and beta(2)-glycoprotein I antibodies (p < 0.048), both from IgG isotype. Only SLE patients without APS revealed a significantly elevated production of reactive oxygen species indicating an increased proatherogenic oxidative stress in the circulation (p < 0.002). In the patient groups, the circulating levels of oxLDL and Anti-oxLDL showed no association with atherosclerosis as estimated by IMT. In conclusion, our experimental data do not support the concept of oxidative stress-induced accelerated atherosclerosis in APS patients.

A dependency model for patients with Alzheimer's disease: its validation and relationship to the costs of care--the LASER-AD Study

BACKGROUND

Loss of independence becomes more marked as Alzheimer's disease (AD) progresses and contributes significantly to its societal and economic burden. Existing measures of functional disability focus either on basic or on instrumental activities of daily living (ADL). It would be more appropriate to combine these but, using existing assessment tools, this would involve considerable quantitative analysis. Recently, a qualitative and pragmatic system of classifying AD patients according to levels of dependency has been developed in a Belgian cohort.

OBJECTIVES

To validate independently, in a UK community setting, a functional classification model of AD patients and to explore the relationship between dependency and costs of care using this model.

RESEARCH DESIGN AND METHODS

Longitudinal epidemiological study of 224 AD patients. Data were collected at baseline and at 6 months on ADL, global state, cognition, behavioural dimensions, depression, quality of life and resource utilisation using validated instruments. An automatic classification algorithm was performed to allow identification of dependency clusters. The scheme was tested for validity against other simultaneously collected data including health and social care costs. The relationship between dependency and costs of care was explored using ANOVA models.

RESULTS

Analysis of the ADL assessment instruments produced three ADL sub-scores by which patients could be classified into one of three disability clusters: ('non-dependent', 'non-dependent with instrumental functional disability', and 'dependent'). Good external validity of the classification scheme was demonstrated by correlation with simultaneously collected data. After a backward selection process on ANOVA model (at a 5% level), institutionalisation and the most dependent status were the most significant cost drivers.

CONCLUSIONS

Qualitative classification of AD patients using dependency levels is a simple and validated approach. Applying this approach showed that institutionalisation and the most 'dependent' status were independently and significantly associated with high care cost.

Multiple antiphospholipid tests do not increase the diagnostic yield in antiphospholipid syndrome

The family of antiphospholipid antibodies (aPL) includes a heterogeneous population of autoantibodies whose specificity is directed against not only phospholipids, but their complex with plasma proteins. Anticardiolipin antibodies (aCL) and lupus anticoagulant (LA) tests are widely performed to screen the aPL family which is associated with thrombotic complications in patients with systemic lupus erythematosus (SLE) or antiphospholipid syndrome (APS). The clinical significance of other aPL tests, including antibodies against phosphatidylserine (aPS), phosphatidylinositol (aPI), phosphatidic acid (aPA), phosphatidylcholine (aPC) and phosphatidylethanolamine (aPE), has not been established. The purpose of this study was to evaluate whether multiple aPL tests have enhanced diagnostic value for APS. We tested IgG/M/A aPS, aPI, aPA, aPC and aPE by ELISA using 10% bovine serum as blocking and sample diluent in 26 SLE patients with clinical manifestations of APS, but negative for both aCL and LA (Group 1). The results were compared with 32 SLE patients without any features of APS (Group 2) and 24 SLE patients with APS (aCL and/or LA positive) (Group 3). In Group 1, 1/26 (4%) was positive for IgA aPE, less frequent than in other groups, and none of the patients had any other aPL. In Group 2, 1/32 (3%) was positive for aPS, two (6%) for aPI, one (3%) for aPA and four (12.5%) for aPE. None was positive for aPC. In the third group, 13/24 (54%) were positive for aPS, 11 (46%) for aPI, 15 (63%) for aPA, four (17%) for aPC and seven (29%) for aPE. Since aPE was found in some patients, we extended the study, including 207 SLE patients, and tested aPE. IgG/M/A aPE was found in six (3%), 10(5%) and 21 (10%), respectively, but no association was found between aPE and any clinical features of APS. This study suggests that screening by multiple aPL tests does not increase the diagnostic yield in APS.

[The antiphospholipid syndrome]

Antiphospholipid syndrome (APS) is a thrombophilic disorder, which embraces almost all specialities. This article includes information about the history, classification, epidemiology, clinical manifestations and treatment of the APS. It is the aim of this article to introduce the APS with clinical features of all medical specialities to show the actuality of the syndrome which is not known everywhere.

The pathogenic 16/6 idiotype in patients with silica associated systemic lupus erythematosus (SLE) and uranium miners with increased risk for development of SLE

OBJECTIVE

To investigate the prevalence of the 16/6 idiotype (16/6 Id), a major cross reactive idiotype of anti-DNA antibodies involved in the pathogenesis of experimental lupus, in subjects with an exogenous risk for the development of systemic lupus erythematosus (SLE).

METHODS

The titer of 16/6 Id was determined by ELISA in sera of uranium miners exposed to heavy quartz dust: 15 developed definite and 12 probable SLE, 34 had clinical symptoms, and 27 had only serological signs (medium to high titer anti-dsDNA antibodies) of possible connective tissue disease (CTD) development.

RESULTS

The prevalence of 16/6 Id was higher in all groups compared to healthy blood donors. It was 18.5% in miners with SLE (definite and probable) and 22.2-26.5% in miners with clinical and/or serological signs for developing CTD. All 16/6 Id positive miners were positive for anti-dsDNA antibodies and other autoantibodies associated with CTD. The prevalence of 16/6 Id in anti-dsDNA positive miners correlated slightly with CTD/SLE symptoms: 55.6% in patients with SLE, 47.4% in miners with possible CTD/SLE, and 22.2% in miners without CTD symptoms. Further, at short term followup, disease progressed in 2 miners of the 16/6 Id positive, but not in 16/6 Id negative miners.

CONCLUSION

The detection of 16/6 Id in miners exposed to quartz dust may indicate a higher risk for development of SLE, warranting further studies of the role of 16/6 Id in the development of SLE in a cohort with the same sex, ethnicity, geographic region, and occupation.

ATP-sensitive K+ channels regulated by intracellular Ca2+ and phosphorylation in normal (T84) and cystic fibrosis (CFPAC-1) epithelial cells

The elementary K+ conductance activated by the cAMP or the Ca2+ second messenger pathways was investigated in the model salt-secreting epithelium, the human T84 cell line. Under Cl(-)-free conditions, an inwardly rectifying whole-cell K+ current was evoked by either forskolin 10 (mumol/l) or acetylcholine 1 (mumol/l) and blocked by extracellular charybdotoxin 10 (nmol/l). In the cell-attached mode, both secretory agonists induced the opening of a channel showing inward rectification with a unitary chord conductance of 36.8 +/- 2.5 pS (n = 26) for inward currents. In inside-out patches, a 35-pS inwardly rectifying K+ channel that corresponded to the channel recorded in the cell-attached configuration was recorded in the presence of 0.3 mumol/l free Ca2+ at the inner side of the membrane. This channel was blocked by Ba2+ (5 mumol/l) and by charybdotoxin (50 nmol/l). Its open probability was enhanced by intracellular Ca2+ with and EC50 of 0.25 mumol/l and strongly reduced by intracellular MgATP with an IC50 of 600 mumol/l. In the continuous presence of ATP, the channel activity was consistently increased by 125 kU/l catalytic subunit of cAMP-dependent protein kinase. In the cystic fibrosis pancreatic duct cell line CFPAC-1, a K+ channel was also recorded, with similar characteristics and regulation as the 35-pS channel in T84 cells. We conclude that an ATP-sensitive K+ channel regulated by intracellular Ca2+ and phosphorylation supports the main K+ current activated by secretory agonists in normal cystic fibrosis cell lines.(ABSTRACT TRUNCATED AT 250 WORDS)

Concomitant activation of Cl- and K+ currents by secretory stimulation in human epithelial cells

1. Whole-cell currents were investigated in the model salt-secreting epithelium, human T84 cell line, by means of the perforated patch-clamp technique. In the control extracellular medium containing Cl-, depolarizing voltage ramps evoked current responses which peaked at 5.43 +/- 0.81 pA pF-1 at +60 mV and had a reversal potential (Erev) of -38.4 +/- 2.5 mV (n = 23). 2. Activation of the cAMP pathway with forskolin increased the current at +60 mV from 3.81 +/- 0.61 to 20.79 +/- 5.08 pA pF-1 (n = 18). In thirteen cells, Erev was initially shifted towards positive potentials (Erev of the cAMP-activated initial current was -18.2 +/- 1.2 mV) and subsequently shifted towards more negative potentials, consistent with the activation of both Cl- and K+ currents during cAMP stimulation. 3. Increasing the intracellular Ca2+ concentration, [Ca2+]i, with ionomycin (1 microM) or with acetylcholine (1 microM), increased the current at +60 mV from 7.79 +/- 1.57 to 57.50 +/- 12.10 pA pF-1 (n = 6) and from 6.36 to 34.13 pA pF-1 (n = 4), respectively. With both agonists, Erev was shifted either towards the reversal potential for potassium, EK, or towards the reversal potential for chloride, ECl, depending on the cell. 4. In the absence of chloride ions (gluconate substituted), stimulation of the Ca2+ pathway activated a time-independent outward current of large amplitude. This current exhibited inward rectification at positive voltages, reverted at -89.5 +/- 0.2 mV and was markedly reduced by charybdotoxin (10 nM), a specific blocker of Ca(2+)-activated K+ channels. When a voltage step protocol was used, increased [Ca2+]i also activated an outward current at potentials more positive than -40 mV which slowly relaxed during depolarizing steps. 5. The activation of both (i) a time-dependent inwardly rectifying charybdotoxin-sensitive K+ current, and (ii) a time-dependent slowly inactivating current was also produced by cAMP stimulation. 6. We concluded that (i) in the T84 epithelial cells, both Cl- and K+ currents are concomitantly increased by secretagogue stimulation, and (ii) two different types of K+ conductances are activated by either the cAMP or the intracellular Ca2+ secreting pathways.

Small and intermediate conductance chloride channels in HT29 cells

Recently, it has been shown that intermediate conductance outwardly rectifying chloride channels (ICOR) are blocked by cytosolic inhibitor (C. I.) found in the cytosol of human placenta and epithelial cells. C. I. also reduced the baseline current in excised membrane patches of HT29 cells. In the present study, this effect of C. I. was characterized further. Heat treated human placental cytosol was extracted in organic solvents and dissolved in different electrolyte solutions. It is shown that the reduction of baseline conductance (g(o)) is caused by inhibition of small non-resolvable channels, which are impermeable to Na+ and SO4(2-), but permeable to Cl-. The regulation of these small Cl(-)-conducting channels (g(o)) and of ICOR was examined further. First, no activating effects of protein kinase A (PKA) on the open probability (Po) of the ICOR or on the g(o)) were observed. The Po of the ICOR was reduced by 22% in a Ca(2+)-free solution. g(o) was insensitive to changes in the Ca2+ activity. The effects of C. I. from a cystic fibrosis (CF) placenta and the CF pancreatic duct cell line CFPAC-1 were compared with the effects of corresponding control cytosols, and no significant differences between CF and control cytosols were found. We conclude that the excised patches of HT29 cells contain ICOR and small non-resolvable Cl(-)-conducting channels which are similarly inhibited by C. I.(ABSTRACT TRUNCATED AT 250 WORDS)