A Phase-1b study of tivantinib (ARQ 197) in adult patients with hepatocellular carcinoma and cirrhosis

BACKGROUND

The mesenchymal-epithelial transition factor (MET) receptor is dysregulated in hepatocellular carcinoma (HCC), and tivantinib (ARQ 197) is an oral, selective, MET inhibitor.

METHODS

This Phase-1b study assessed tivantinib safety as primary objective in patients with previously treated HCC and Child-Pugh A or B liver cirrhosis. Patients received oral tivantinib 360 mg twice daily until disease progression or unacceptable toxicity.

RESULTS

Among 21 HCC patients, common drug-related adverse events (AEs) were neutropaenia, anaemia, asthenia, leucopaenia, anorexia, diarrhoea, and fatigue. No drug-related worsening of liver function or performance status occurred, but one Child-Pugh B patient experienced drug-related bilirubin increase. Four patients had drug-related serious AEs, including one neutropaenia-related death. Haematologic toxicities were more frequent than in previous tivantinib studies but were manageable with prompt therapy. Best response was stable disease (median, 5.3 months) in 9 of 16 evaluable patients (56%). Median time to progression was 3.3 months.

CONCLUSION

Tivantinib demonstrated a manageable safety profile and preliminary antitumour activity in patients with HCC and Child-Pugh A or B cirrhosis.

Mechanisms linking obesity, inflammation and altered metabolism to colon carcinogenesis

Due to its prevalence, obesity is now considered a global epidemic. It is linked to increased risk of colorectal cancer, the third most common cancer and the second leading cause of death among adults in Western countries. Obese adipose tissue differs from lean adipose tissue in its immunogenic profile, body fat distribution and metabolic profile. Obese adipose tissue releases free fatty acids, adipokines and many pro-inflammatory chemokines. These factors are known to play a key role in regulating malignant transformation and cancer progression. Obese adipose tissue is infiltrated by macrophages that participate in inflammatory pathways activated within the tissue. Adipose tissue macrophages consist of two different phenotypes. M1 macrophages reside in obese adipose tissue and produce pro-inflammatory cytokines, and M2 macrophages reside in lean adipose tissue and produce anti-inflammatory cytokines, such as interleukin-10 (IL-10). The metabolic networks that confer tumour cells with their oncogenic properties, such as increased proliferation and the ability to avoid apoptosis are still not well understood. We review the interactions between adipocytes and immune cells that may alter the metabolism towards promotion of colorectal cancer.

Emergency Medical Services: a resource for victims of domestic violence?

BACKGROUND

Domestic violence (DV), also known as intimate partner violence (IPV), is one of the leading causes of serious injury among women of childbearing age. As first responders on the scene during DV calls where personal injuries have occurred, Emergency Medical Services (EMS) could routinely identify, report and assist victims of violence. Yet, little is known of the prevalence of DV calls in EMS practice, Emergency Medical Technicians' (EMT) knowledge and comfort in responding to such calls, or how they care for victims.

METHOD

The objectives of this study were to assess EMTs' knowledge of and experience with providing care to victims of DV in the province of Ontario, Canada. Data were gathered through an online, short-answer survey. Survey data were analysed using basic frequency displays, and descriptive statistics are reported.

RESULTS

Almost 500 EMTs participated in this study, the vast majority of whom (90%) attended at least one DV call in the preceding year, with 65% attending between 10 and 20 DV calls. The majority of respondents (84.5%) wished for more education and training on the issue.

CONCLUSION

EMTs have frequent contact with victims of DV yet have received little education about the issue. The majority of those surveyed would like specific education and training on DV.

Heart rate monitoring as a reliable tool for assessing energy expenditure in obese individuals

Previous studies have suggested the use of the FlexHR method for predicting daily energy expenditure in various populations. We investigated the stability of the relation between oxygen consumption (VO2) and heart rate (HR) in obese subjects undergoing a fitness and weight reduction program. Eleven obese (BMI>30) healthy subjects (6 males, 5 females) were recruited from a Wellness program. Subjects performed a laboratory calibration procedure between HR and VO2 in resting and exercising conditions, before starting the Wellness program (Stage I) and after reducing 10% of their initial body weights (BW) within 6 months (Stage II). Mean BW, BMI and % body fat were reduced by 13.1±4.4 kg, 4.2±1.4 kg.m-2 and 6.8±4.1%, respectively, for all parameters (P<0.001). Mean peak VO2 increased from 31.3±7.1 at the beginning to 37.2±7.3 mL.kg-1.min-1 at the end of the intervention period (P<0.01). The mean flex HR point changed from 96±14 to 86±15 beats.min-1 (P<0.05). There were no significant individual differences in the HR-VO2 prediction equations derived from the laboratory calibrations in either stage. In conclusion, the relationship between HR and VO2 consumption remains stable during a time period of weight reduction. The use of the FlexHR method for predicting energy expenditure by heart rate monitoring is recommended for subjects undergoing a weight-reduction program. It should be taken in account, however, that an increase in aerobic capacity, in parallel to changes in body weight and composition, might cause a decrease in the flex point.

Studies of operant and reflexive key pecks in the pigeon

The duration of pigeons' key pecks was studied in three experiments. Experiment I revealed that key pecks early in exposure to continuous reinforcement were of short duration, as were key pecks observed on an omission procedure in which pecks prevented food delivery. Key pecks later in exposure to continuous reinforcement, and those that occurred on positive automaintenance procedures, were of long duration. In Experiment II, pigeons were exposed to fixed-interval and fixed-ratio reinforcement schedules, and durations were recorded separately for each quarter of each interval or ratio. On fixed interval, durations were shorter in the first quarter of each interval than in subsequent quarters; on fixed ratio, durations were longer in the first quarter of the ratio than in subsequent quarters. These data parallel observations of concurrent operant responding and salivation in dogs. In Experiment III, pigeons were exposed to a discrete trial, differential-reinforcement-of-low-rate 6-sec schedule. Durations of responses in the first 2 sec of the trial were substantially shorter than those of responses that occurred later. The data from all three experiments support the view that the pigeon's "key peck" actually consists of two subclasses of peck, one reflexive and one operant.

Two types of pigeon key pecking: suppression of long- but not short-duration key pecks by duration-dependent shock

The key pecking of eight pigeons was maintained on a variable-interval 1-minute schedule of food reinforcement. Sometimes, all responses between 35 and 50 milliseconds in duration produced a shock; sometimes, all responses between 10 and 25 milliseconds produced a shock; sometimes, shocks were produced by pecks without regard to duration (nondifferential punishment), and sometimes shocks were delivered independently of responding. Punishment of 35- to 50-millisecond responses selectively suppressed those responses, while punishment of 10- to 25-millisecond responses and nondifferential punishment suppressed responding overall but did not suppress responses of particular duration. Punishment of 35- to 50-millisecond responses suppressed key pecking slightly less than did nondifferential punishment. Punishment of 10- to 25-millisecond responses and response-independent shock produced roughly equal amounts of suppression, substantially less than the other punishment procedures. The data support the view that there are at least two kinds of key peck, identifiable on the basis of duration, one of which (short duration) is insensitive to its consequences.

Stimulus-reinforcer contingencies and local behavioral contrast

Four pigeons were exposed to a series of multiple schedules of variable-interval reinforcement in which pecks were required on one key (operant key) and components were signalled on a second key (signal key). Four additional pigeons experienced identical conditions, except that a yoking procedure delivered food on variable-time schedules, with no key pecks required. One of the components of the multiple schedule was constant throughout the experiment as a variable-interval (or variable-time) 30-second schedule. Operant-key responding during the constant component was uniform throughout the component, uninfluenced by changes in the duration of the variable component, and only slightly influenced by changes in reinforcement frequency correlated with the variable component. By comparison, signal-key response rate during the constant component was highest at the onset of the component, was higher when the variable component was 60-sec long than when it was 1-sec long, and was higher when no reinforcement occurred in the variable component than when reinforcement was scheduled in the variable component. These characteristics of signal-key pecking matched characteristics of local positive behavioral contrast. These data are taken to support the "additivity theory" of behavioral contrast and to suggest that Pavlovian stimulus-reinforcer relations contribute primarily to the phenomenon of local positive contrast.

Effects of reinforcement magnitude on pigeons' preference for different fixed-ratio schedules of reinforcement

In concurrent, two-member chains, the completion of one or the other of two initial percentage fixed-interval 90-sec links produced a terminal link in which the completion of a fixed ratio produced food reinforcement. The fixed ratios and the duration of reinforcement in the terminal links were varied. Relative response rate in initial links was proportional to the relative reinforcement duration per ratio response (reinforcement duration divided by fixed ratio) in terminal links. The rate of responding in the terminal fixed-ratio links was insensitive to both ratio size and reinforcement duration and therefore did not vary sufficiently to distinguish between responses per reinforcement and immediacy of reinforcement as controlling variables in terminal links.

Interval and ratio reinforcement of a complex sequential operant in pigeons

Pigeons were required to produce exactly four pecks on each of two keys in any order for reinforcement. Correct response sequences were reinforced on either fixed-interval two-minute or fixed-ratio four schedules, with each correct sequence treated as a single response. Each pigeon developed a particular dominant sequence that accounted for more than 80% of all sequences. Sequence stereotypy was relatively unaffected by the temporal properties of the fixed-interval and fixed-ratio schedules. Response time (time from the first response in each sequence to the last) was also relatively unaffected by the temporal properties of the schedules. In contrast, response latency (time from end of one sequence to the beginning of the next) was markedly affected by the schedules. Latencies were long early in the interreinforcement interval and got shorter as the interreinforcement interval progressed. These data suggest that stereotyped response sequences become functional behavioral units, resistant to disruption or alteration by reinforcement variables that ordinarily influence the temporal spacing of individual responses.

The role of the response-reinforcer contingency in negative automaintenance

When a response key is briefly illuminated before a grain reinforcer is presented, key pecking is reliably developed and maintained in pigeons, even if pecking prevents reinforcement (negative automaintenance). This experiment demonstrated that pigeons are sensitive to a negative response-reinforcer contingency, even though it does not eliminate responding. Within individual pigeons, two kinds of trials were compared: red key trials, in which reinforcement was negatively contingent on responding, and white key trials, in which reinforcement was unrelated to responding. Reinforcement frequency in non-contingent trials was yoked to the obtained reinforcement frequency in negatively contingent trials. All eight pigeons pecked substantially more on the non-contingent key than on the negative key, and preferred the non-contingent key to the negative key on occasional "choice" trials where both were presented together. When the stimuli correlated with the two conditions were reversed, the pigeons' behavior also shifted. These response differences are taken as evidence that pigeons are sensitive to the negative response-reinforcer contingency.

The maintenance of key pecking by stimulus-contingent and response-independent food presentation

Three naive pigeons were exposed to a series of two-component multiple schedules of response-independent food presentation. The component schedules were sometimes identical (non-differential procedures) and sometimes different (differential procedures). High rates of key pecking were maintained in all the differential procedures, and pecking decreased substantially in non-differential procedures, even when the frequency of food presentation in non-differential procedures was higher than in differential procedures. It is suggested that the high rates of key pecking were maintained not by adventitious response-reinforcer contingencies, but by differential contingencies between the stimulus (keylight) and food. The role of such contingencies in the phenomenon of behavioral contrast is discussed.

Discrete-trials spaced responding in the pigeon: the dependence of efficient performance on the availability of a stimulus for collateral pecking

Four pigeons were exposed to a discrete-trial schedule in which only responses spaced by at least 6 sec were reinforced. After 45, fifty-trial sessions, they failed to meet the spacing requirement in over 90% of the trials. When an alternative, non-contingent key (pecks on which had no consequence) was illuminated concurrently with the first key, the spacing performance of the three pigeons that pecked the non-contingent key improved so that they were obtaining 75% of the possible reinforcers. These data demonstrated the importance of collateral behavior in mediating spaced performance. It was suggested that pigeons may successfully refrain from responding on the spacing procedure only when another stimulus correlated with reinforcement is available for pecking, and that the form that collateral behavior takes may, in general, be non-arbitrary, and species dependent.

Development of complex, stereotyped behavior in pigeons

A pigeon's peck on one key moved a light down one position in a 5x5 matrix of lights, while a peck on another key moved the light across one position. Reinforcement depended upon the occurrence of four pecks on each key (moving the matrix light from the top left to the bottom right), and a fifth peck on either key ended a trial without food. Though there were 70 different sequences that led to reinforcement, each of 12 pigeons developed a particular, stereotyped sequence which dominated its behavior (Experiment 1). Extinction produced substantial increases in sequence variability (Experiment 2). Removal of the matrix cues disrupted performance, though it partially recovered with extended training (Experiment 3). The pigeons did not master a contingency which required a different sequence on the current trial than on the previous one (Experiment 4), though they were able to learn to emit sequences which began with either left-left or left-right response patterns (Experiment 5). The experiments suggest that contingencies of reinforcement may contribute to the creation of complex units of behavior, and that stereotypy may be a likely consequence of contingent reinforcement.

Discriminative stimulus location as a determinant of positive and negative behavioral contrast in the pigeon

Four pigeons were exposed to a series of two-component multiple schedules of reinforcement that ordinarily yield positive and negative behavioral contrast. The stimuli that signalled the component schedules were sometimes located on the response key and sometimes off. Positive behavioral contrast was observed only when the stimuli were on the key. Negative contrast was observed independent of stimulus location. These data suggest that positive and negative contrast may be causally unrelated, and support an account of contrast in terms of the summation of key pecks that are separately controlled by response-reinforcer and stimulus-reinforcer dependencies.

Behavioral contrast in the pigeon: a study of the duration of key pecking maintained on multiple schedules of reinforcement

Pecks on an operant key were reinforced on either multiple variable-interval variable-interval or multiple variable-interval extinction schedules of reinforcement. The stimuli that signalled the multiple-schedule components were located on a second key (signal key), and a changeover delay prevented reinforcement of signal key-peck-operant key-peck sequences. No behavioral contrast was observed on the operant key, and appreciable responding to the signal key occurred during the variable-interval component of the multiple variable-interval extinction procedure. Peck durations on the signal key were markedly shorter than peck durations on the operant key. Moreover, most responses on the signal key occurred just after the multiple-schedule components changed. These data support an account of behavioral contrast in terms of the summation of pecks that are separately controlled by stimulus-reinforcer and response-reinforcer dependencies, and suggest that the stimulus-reinforcer dependency is responsible primarily for local contrast. In addition, the data suggest that pecks that are controlled by these two dependencies may belong to topographically different classes.

Failure to produce response variability with reinforcement

Two experiments attempted to train pigeons to produce variable response sequences. In the first, naive pigeons were exposed to a procedure requiring four pecks on each of two keys in any order, with a reinforcer delivered only if a given sequence was different from the preceding one. In the second experiment, the same pigeons were exposed to this procedure after having been trained successfully to alternate between two specific response sequences. In neither case did any pigeon produce more than a few different sequences or obtain more than 50% of the possible reinforcers. Stereotyped sequences developed even though stereotypy was not reinforced. It is suggested that reinforcers have both hedonic and informative properties and that the hedonic properties are responsible for sterotyped repetition of reinforced responses, even when stereotypy is negatively related to reinforcer delivery.

Allocation of complex, sequential operants on multiple and concurrent schedules of reinforcement

Pigeons could produce food by pecking exactly four times on each of two keys, in any order. In the first experiment, these response sequences were reinforced on a series of multiple schedules of variable-interval reinforcement. In the second experiment, these response sequences were reinforced on a series of concurrent schedules of reinforcement. In both experiments, highly stereotyped response sequences developed. If these response sequences were treated as individual responses, the resulting data conformed to what is typically reported in studies of multiple and concurrent schedules involving individual responses. For example, behavioral contrast was observed with the multiple schedules, and matching was observed with the concurrent schedules. However, schedule manipulation had no effect on within-sequence characteristics of responses like accuracy, stereotypy, or rate. These data constitute further evidence that response sequences can become functional behavioral units.