The role of clinicopathologic and molecular prognostic factors in the post-mastectomy radiotherapy (PMRT): a retrospective analysis of 912 patients.

OBJECTIVE: To assess the association of clinicopathologic and molecular features with loco-regional recurrence (LRR) in post-mastectomy breast cancer patients with or without adjuvant radiotherapy (PMRT). PATIENTS AND METHODS: We retrospectively reviewed data of patients undergone to mastectomy followed or not by PMRT between January 2004 and June 2013. The patients were divided according to clinicopathologic and molecular sub-classification features. LRR and Cancer Specific Survival (CSS) were calculated using the Kaplan-Meier method; the prognostic factors were compared using long-rank tests and Cox regression model. RESULTS: A total of 912 patients underwent to mastectomy of whom 269 (29.5%) followed by PMRT and 643 (70.5%) not; among the PMRT group, 77 underwent to the chest wall (CW) and 202 to the chest wall and lymphatic drainage (CWLD) irradiation. The median follow-up was 54 months (range, 3-118). No significant difference in terms of LRR and CSS was found between non-PMRT and PMRT group (p=0.175; and p=0.628). The multivariate analysis of LRR for patients who did not undergo PMRT showed a significant correlation with the presence of extracapsular extension (ECE) (p=0.049), Ki-67>30% (p=0.048) and triple negative status (p=0.001). In the PMRT group, triple negative status resulted as the only variable significantly correlated to LRR (p=0.006) at the multivariate analysis and T-stage also showed a trend to significance (p=0.073). Finally, no difference in LRR control was shown between CW and CWLD-PMRT (p=0.078). CONCLUSIONS: After mastectomy ECE, a cut off of Ki-67>30% and triple negative status were strictly correlated with LRR regardless of clinicopathologic stage. PMRT has a positive impact in decreasing LRR in patients with this molecular profile. Besides, CW might represent a valid option for patients with one to three positive nodes.

Homotaurine: a GABAB antagonist in guinea-pig ileum.

Homotaurine (3-aminopropane sulphonic acid) did not inhibit the twitch response in guinea-pig ileum longitudinal muscle whilst gamma-aminobutyric acid (GABA) and (-)-baclofen evoked dose-dependent inhibitions. The inhibitory effects of GABA and (-)-baclofen were prevented in the presence of homotaurine 2 X 10(-4) and 10(-3) M. The log dose-effect curves of GABA and (-)-baclofen were shifted in a parallel manner compatible with competitive antagonism. The pA2 of homotaurine with GABA (4.22 +/- 0.05) and (-)-baclofen (4.26 +/- 0.1) were the same. Homotaurine did not antagonize the inhibitory effects of morphine (ED50 4 X 10(-7) M), noradrenaline (ED50 10(-6) M) or ATP (ED50 1.5 X 10(-5) M). The inferior homologue of homotaurine, taurine 10(-3) M, did not modify the inhibitory effects of GABA and (-)-baclofen. Picrotoxin 5 X 10(-5) M antagonized GABAA receptor-mediated contraction but did not affect GABAB receptor-mediated inhibition. At the same concentration the drug did not influence the antagonistic action of homotaurine, thus showing no GABAA receptor-mediated interference. It may be concluded that homotaurine is a competitive antagonist of GABAB mediated effects in the guinea-pig ileum.

GABAA and GABAB receptor-mediated effects in guinea-pig ileum.

1 The effects of gamma-aminobutyric acid (GABA) and related substances were examined in guinea-pig ileum longitudinal muscle.2 GABA at doses ranging from 10(-7) M to 3 x 10(-6) M elicited a relaxation while at higher doses (3 x 10(-6) M - 10(-4) M), as previously described, it caused a contraction followed by relaxation.3 GABA-induced relaxation was bicuculline-insensitive, was mimicked by (-)-baclofen but not by homotaurine and muscimol. The effect of baclofen was stereospecific. GABA- and (-)-baclofen-induced relaxations were dose-dependent and their ED(50) values were similar. A specific cross-desensitization occurred between GABA and (-)-baclofen.4 The bicuculline-insensitive relaxation induced by GABA and (-)-baclofen was prevented by tetrodotoxin and hyoscine but not by phentolamine plus propranolol, naloxone or theophylline.5 In preparations in which the muscle tone was raised by histamine or prostaglandin F(2alpha), GABA and (-)-baclofen induced relaxation to the same extent as before increasing the tone. If the tone was raised by DMPP, a greater bicuculline-insensitive relaxation occurred.6 Contraction caused by GABA was bicuculline-sensitive and was mimicked by homotaurine and muscimol. Contraction was dose-dependent and muscimol was about three times more potent than GABA or homotaurine. A specific cross-desensitization occurred between the contractile effects of GABA and those of homotaurine or muscimol.7 Bicuculline competitively antagonized the contractile effects of GABA, homotaurine and muscimol and gave closely similar pA(2) values. The slope of the Schild plot for the above drugs was near 1, confirming the competitive nature of the antagonism.8 The bicuculline-sensitive contraction induced by GABA, homotaurine and muscimol was abolished by tetrodotoxin and was non-competitively antagonized by hyoscine, while it was unaffected by hexamethonium, mepyramine and methysergide.9 It is concluded that two receptors mediate the GABA effects in guinea-pig ileum: a bicuculline-sensitive GABA(A) receptor, which elicits contraction through an excitatory action on cholinergic post-ganglionic neurones; and a bicuculline-insensitive GABA(B) receptor which causes relaxation through an inhibitory presynaptic action on cholinergic post-ganglionic neurones. We confirm that GABA, homotaurine and muscimol are GABA(A) agonists, while GABA and (-)-baclofen are GABA(B) agonists.

Modulatory activity of GABAB receptors on cholinergic tone in guinea-pig distal colon.

The effect of gamma-aminobutyric acid (GABA) administration was studied in both in vitro and in vivo preparations of the guinea-pig distal colon. In in vitro preparations GABA (10(-7) - 10(-3) M) elicited a dose-dependent relaxation; a decrease in the spontaneous contractions was sometimes observed. The effect of GABA was mimicked by (-)-baclofen, which gave a dose-response curve overlapping that of GABA, while (+)-baclofen was about one hundred times less potent. The relaxation responses induced by the above drugs were antagonized by 5-aminovaleric acid (5 X 10(-4) M), which did not affect adenosine-induced relaxation, but they were insensitive to bicuculline (10(-5) M) and picrotoxin (10(-5) M). Moreover, they were prevented by tetrodotoxin (6 X 10(-7) M). In hyoscine (10(-7) M)-pretreated preparations, GABA still evoked a small relaxation response (approx. 10% of the maximum) that was bicuculline-sensitive. Desensitization to GABA (10(-5) M) was observed. A specific cross-desensitization occurred between GABA (10(-5) M) and (-)-baclofen (10(-5) M). In in vivo preparations, GABA (10 mumol kg-1) and (-)-baclofen (5 mumol kg-1) produced a dose-related inhibition of basal tone, while (+)-baclofen (5 mumol kg-1) had much less effect (about 25%). A decrease in the spontaneous contractions was sometimes observed. The relaxant effect of GABA and (-)-baclofen persisted in guinea-pigs pretreated (1-2 min) with picrotoxin (1.6 mumol kg-1), whereas it was significantly reduced in animals injected 1 min beforehand with 5-aminovaleric acid (0.2 mmol). The maximal relaxant effect induced by GABA and (-)-baclofen did not differ from that of atropine (0.9 mumol kg-1) and after atropine administration GABA had no further inhibitory effect. Relaxation responses induced by GABA and (-)-baclofen still occurred after blockade of nicotinic receptors by hexamethonium (0.17 mmol kg-1), which itself caused an increase in the basal tone. When the tone was increased by topical application of physostigmine (40 micrograms), GABA and (-)-baclofen induced a greater relaxation than that obtained in basal conditions. It is concluded that GABA, both in vitro and in vivo administration, inhibits cholinergic tone in guinea-pig distal colon and that this effect is mediated mainly by activation of GABAB receptors. Further experiments are required to ascertain the possible physiological role of a GABA-releasing neuronal system in the colon in vivo.

A phase I-II study of oral doxifluridine plus radiotherapy in radiosensitive tumors of the pelvic region.

AIMS AND BACKGROUND: Fluoropyrimidines have shown synergic effects in combination with radiotherapy in several tumor types. Doxifluridine is a novel 5-fluorouracil (5-FU) prodrug which is transformed into 5-FU in neoplastic tissue. This would imply enhancement of radiotherapy by 5-FU in neoplastic tissue, where the drug is concentrated higher than in surrounding healthy tissues. METHODS: A phase I-II study was carried out on 10 patients with radiosensitive tumors of the pelvic area (4 uterine carcinomas). Escalating doses of oral doxifluridine were administered in combination with standard radiotherapy to assess the efficacy and toxicity profile of the combined treatment. The 9 evaluable patients (3 groups of 3 patients each) received oral doxifluridine, at daily doses of 500, 750, or 1000 mg, for 6 consecutive weeks in combination with a standard (1.8-2.0 Gy) dose of radiotherapy. Assessment of physical and laboratory parameters was made at baseline, then weekly up to the end of the treatment and at follow-up. RESULTS: At the final evaluation, one patient with a diagnosis of uterine carcinoma showed a complete response that lasted 10 weeks. One patient had a partial response, and 7 patients had no change. The most frequent adverse events were gastrointestinal: 27 episodes of mild to moderate nausea/vomiting and diarrhea. Three patients complained of severe diarrhea of 5-7 days duration: all patients spontaneously recovered. There were no significant changes in laboratory or clinical parameters, and no serious toxicity requiring reduction or interruption of the radiotherapy. CONCLUSIONS: The maximum tolerated dose of oral doxifluridine in combination with standard radiotherpay was assessed at 1000 mg/patient/day (equivalent to 36-38 g monthly, previously reported as mTD in phase I studies).

5-Aminovaleric acid interactions with GABAA and GABAB receptors in guinea-pig ileum.

The potential interaction of 5-aminovaleric acid (5-AVA) on GABAA and GABAB receptors was investigated on the guinea-pig isolated ileum myenteric plexus preparation. In the unstimulated preparation 5-AVA (0.1-3 mM) produced a transient contraction which was abolished by previous exposure to picrotoxin (0.1 mM), atropine (3 microM) or tetrodotoxin (0.3 microM). Cross desensitization was observed between the contractile effects of 5-AVA and GABA, while a previous exposure to (+/-)-baclofen did not affect 5-AVA induced contractions. 5-AVA antagonized the relaxant effect of (+/-)-baclofen in unstimulated preparations. 5-AVA (1 mM) had no effect on amplitude of twitches in supramaximally stimulated preparations while GABA produced a concentration related inhibition. In the presence of 5-AVA (1 mM) the concentration response curve to GABA was shifted to the right without a reduction of the maximal effect attainable. These observations indicate that 5-AVA interacts with both GABAA and GABAB receptors in guinea-pig ileum. The concentrations required to observe a GABAA effect are of the same order as those which are effective in producing a blockade of GABAB mediated responses.

Inhibition of anaphylactic histamine release in vitro by GABA.

Inhibitory effect of GABA on anaphylactic histamine release in vitro is not mimicked by 2-aminoethansulphonic acid (taurine), an aminoacid unrelated to GABA neuro-transmission. Tetrodotoxin (TTX) 6 X 10(-7) M, a concentration known to block neuronal mechanism but not to modify muscle membrane and anaphylactic histamine release, strongly prevented the inhibition caused by GABA in the Schultz-Dale reaction and in anaphylactic histamine release. The inhibitory effect of GABA on anaphylactic reaction in vitro thus appears to be specific for this aminoacid and is neurogenic in nature, in that it requires integrity of neuronal mechanisms.

Influence of GABA on anaphylactic histamine release in vitro.

In this preliminary report an unreported inhibitory action of GABA on anaphylactic reaction has been described. In a functional model (Schultz-Dale reaction) GABA has been demonstrated to inhibit the antigen-evoked contraction. This effect depends on a modulation of anaphylactic histamine release. The phenomenon is dose-dependent and requires a period of time to develop. Since GABAergic neurons are present in the preparation, it is possible to speculate that GABA receptors are involved in this inhibitory action. However, pharmacological analysis of the phenomenon has to be carried out, especially in view of the latency of GABA to develop its effect.

Diazepam potentiates GABA-contraction in guinea-pig ileum.

Both GABA-receptors and benzodiazepine receptors have recently been described in the ileum. In this work we tested whether an interaction between diazepam and GABA-A- or GABA-B-mediated effects took place in guinea-pig ileum longitudinal muscle. We found that diazepam dose-dependently (10(-9) M-10(-6) M) potentiates the contractions caused by the activation of GABA-A receptor while it is ineffective at the same doses on GABA-B- mediated effects (relaxation and inhibition of twitch response). The drug "per se" does not affect the ileum. Diazepam potentiation is specific since this drug does not potentiate contractions caused by acetylcholine (10(-8) M), 5-HT (10(-7) M), histamine (10(-7) M), and electrical stimulation. Diazepam potentiating effect was not evident in the presence of bicuculline (10(-5) M) or hyoscine (2 X 10(-7) M). Ro 15-1788 (10(-5)M) and beta CCE (10(-5)M) antagonized diazepam potentiation of GABA contraction, while PK 11195 (10(-5) M) was ineffective. We conclude that diazepam modulates the effects evoked by stimulation of peripheral GABA-A receptors, while it is ineffective on GABA-B mediated effects.