Treatment outcome of atypical EGFR mutations in the German National Network Genomic Medicine Lung Cancer (nNGM).

BACKGROUND: Atypical EGFR mutations occur in 10%-30% of non-small-cell lung cancer (NSCLC) patients with EGFR mutations and their sensitivity to classical epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitors (TKI) is highly heterogeneous. Patients harboring one group of uncommon, recurrent EGFR mutations (G719X, S768I, L861Q) respond to EGFR-TKI. Exon 20 insertions are mostly insensitive to EGFR-TKI but display sensitivity to exon 20 inhibitors. Clinical outcome data of patients with very rare point and compound mutations upon systemic treatments are still sparse to date. PATIENTS AND METHODS: In this retrospective, multicenter study of the national Network Genomic Medicine (nNGM) in Germany, 856 NSCLC cases with atypical EGFR mutations including co-occurring mutations were reported from 12 centers. Clinical follow-up data after treatment with different EGFR-TKIs, chemotherapy and immune checkpoint inhibitors were available from 260 patients. Response to treatment was analyzed in three major groups: (i) uncommon mutations (G719X, S7681, L861Q and combinations), (ii) exon 20 insertions and (iii) very rare EGFR mutations (very rare single point mutations, compound mutations, exon 18 deletions, exon 19 insertions). RESULTS: Our study comprises the largest thus far reported real-world cohort of very rare EGFR single point and compound mutations treated with different systemic treatments. We validated higher efficacy of EGFR-TKI in comparison to chemotherapy in group 1 (uncommon), while most exon 20 insertions (group 2) were not EGFR-TKI responsive. In addition, we found TKI sensitivity of very rare point mutations (group 3) and of complex EGFR mutations containing exon 19 deletions or L858R mutations independent of the combination partner. Notably, treatment responses in group 3 (very rare) were highly heterogeneous. Co-occurring TP53 mutations exerted a non-significant trend for a detrimental effect on outcome in EGFR-TKI-treated patients in groups 2 and 3 but not in group 1. CONCLUSIONS: Based on our findings, we propose a novel nNGM classification of atypical EGFR mutations.

Effects of chronic morphine treatment on responding for intracranial stimulation in female versus male rats.

Morphine was administered to Sprague-Dawley rats twice daily at 0, 3, 10, and 20 mg/kg/ injection during Weeks 1, 2, 3, and 4, respectively; responding for medial forebrain bundle stimulation was assessed 1, 2, and 3 hr after morning injections in female versus male rats. There were no sex differences in responding under control conditions (Week 1). Morphine's effect on response rate depended on dose, time post-injection, stimulation frequency, and day of treatment. Significant sex differences in morphine's effects occurred at 10 mg/kg, which decreased responding more in males at 1 hr and increased responding more in females at 2 hr, at some frequencies and on some test days. Similar trends were observed at other frequencies, test days, and doses. Morphine's differential effect in males versus females in this procedure suggests that sex comparisons of opioid effects in many animal models may be influenced by sex differences in opioid effects on behavioral output.

Sex differences in development of morphine tolerance and dependence in the rat.

RATIONALE: Several investigators have shown that male rodents are more sensitive than females to morphine's antinociceptive effects. OBJECTIVE: The present study was conducted to determine whether this sex difference is stable after chronic morphine treatment. RESULTS: Acutely administered morphine produced significantly greater hotplate and tail withdrawal antinociception in males than in females. In contrast, there were no sex differences in morphine's hotplate or tail withdrawal effects under repeated (1-week interval) dosing conditions. In a separate group of rats, after 2 weeks of twice-daily morphine treatment (10-20 mg/kg per injection), the ED50 for morphine's antinociceptive effects increased approximately 6.9-fold in males versus only 3.7-fold in females; chronic morphine treatment also disrupted the estrous cycle of females. In a separate group of rats treated with 10 mg/kg morphine twice daily for 5 days, treatment with naloxone (1.0 mg/kg) on day 6 produced greater withdrawal scores in males than in females. CONCLUSIONS: These experiments demonstrate sex differences in development of tolerance to and dependence on morphine in the rat.

Intracranial self-stimulation in female and male rats: no sex differences using a rate-independent procedure.

Given gender differences in human drug use and dependence, this study examined sex differences in reinforcement processes that may underlie such behavior. A psychophysical determination of reinforcement threshold was made using an intracranial self-stimulation (ICSS) paradigm, electrically activating the medial forebrain bundle (MFB) as it passes through the lateral hypothalamus (LH). Using this response rate-independent procedure, basal reinforcement thresholds were not significantly different in male vs. female rats (119.4 +/- 3.3 microA vs. 110.8 +/- 4.0 microA, respectively; N = 8/sex). Further, baseline reinforcement threshold did not fluctuate systematically across stages of the estrous cycle in female rats. The psychostimulants D-amphetamine (0.056-0.56 mg/kg s.c.) and cocaine (1.8-18.0 mg/kg i.p.) dose-dependently lowered reinforcement threshold, with no significant sex difference. The opioid morphine (0.56-5.6 mg/kg s.c.) did not significantly lower reinforcement threshold in either sex. These results contrast those of some previous studies that have used response rate-dependent measures of reinforcement threshold; procedures which are less rate-dependent may be more appropriate when examining subject variables such as sex and stage of estrous.

Sex differences in discriminative stimulus effects of morphine in the rat.

Nine female and ten male rats were trained to discriminate 3.0mg/kg s.c. morphine from saline. The six female rats that acquired and maintained the morphine discrimination did so in significantly fewer sessions than the eight males did (28 +/- 5 vs 51 +/- 9 sessions, respectively), and the ED(50) for morphine substitution was significantly lower in females (0.69 +/- 0.15 vs 1.28 +/- 0.20mg/kg). The time course of morphine substitution was approximately equivalent in females and males. The µ agonist fentanyl completely substituted for morphine in both sexes, with no sex difference in potency to substitute for morphine. The µ agonist buprenorphine partially or completely substituted for morphine in all females and five of six males, but at a lower dose in females (ED(50) 0.009 +/- 0.002 vs 0.019 +/- 0.006mg/kg). The delta agonist BW373U86 partially substituted for morphine in both sexes, with no potency differences; the kappa agonist U69,593 and the non-opioid cocaine did not substitute for morphine in either sex. On a test of spontaneous locomotor activity, morphine increased locomotion to a slightly but not significantly greater extent in males than in females. Morphine also produced significantly greater hotplate antinociception in males than in females. Further drug discrimination training with a lower dose of morphine, 1.0mg/kg, decreased the ED(50) for morphine substitution in females and males to 0.26 +/- 0.06 vs 0.45 +/- 0.11mg/kg, respectively (not significant). In a separate group of age-matched rats, there was no sex difference in brain or plasma levels of morphine measured via HPLC 20min post-injection, the pretreatment time used to examine behavioral effects of morphine. The HPLC results, plus the fact that sex differences were not the same for all behavioral effects of morphine, suggest that sex differences in discriminative stimulus effects of morphine are not due to differential pharmacokinetics. The possibility that sex differences in morphine discrimination reflect sex differences in opioid receptor pharmacology, or differential reinforcement between morphine and saline levers for males but not females, is discussed.

Discriminative stimulus effects of cocaine in female versus male rats.

Eight female and 8 male rats were trained to discriminate 5.6 mg/kg i.p. cocaine from saline on 2-lever, food-reinforced drug discrimination procedure. Female rats acquired the cocaine discrimination in approximately the same number of sessions that males did (43 +/- 7 vs. 51 +/- 9 sessions, respectively), and the ED50 for cocaine discrimination was nearly equivalent in female and male rats (2.46 +/- 0.41 vs. 2.32 +/- 0.49 mg/kg, respectively). The time course for cocaine discrimination was similar in female and male rats, except the offset of cocaine's effects occurred significantly earlier in females than in males. D-Amphetamine dose-dependently substituted for cocaine in all 7 males and 6 of 7 females tested, with no significant sex difference in the ED50 values for D-amphetamine substitution. None of the three opioid agonists tested, morphine (mu), U69,593 (kappa) or BW373U86 (delta), fully substituted for cocaine in rats of either sex. The dopamine antagonist fluphenazine blocked the discriminative stimulus effects of cocaine to approximately the same extent in both sexes. Further drug discrimination training with a higher dose of cocaine, 10 mg/kg, did not significantly alter the ED50 for cocaine discrimination, and there was still no significant sex difference in ED50 values (3.50 +/- 0.39 vs. 2.36 +/- 0.41 mg/kg in females vs. males, respectively). In these same rats, however, cocaine (1-10 mg/kg) produced significantly greater locomotor activation in females than in males on a test of spontaneous locomotor activity. Thus, these results suggest that there are few sex differences in discriminative stimulus effects of cocaine, even at doses that produce significantly different locomotor responses in female versus male rats.