Clinical Outcomes of Patients with Brain Metastases from Colorectal Cancer Treated with Stereotactic Radiosurgery

PURPOSE/OBJECTIVE(S)

Prior studies have demonstrated that brain metastases from gastrointestinal (GI) primary cancers have a poorer response to stereotactic radiosurgery (SRS) when compared to patients with other primary sites, with reported local control of 62-74%. We report our institutional outcomes for patients with colorectal primary cancer who were treated with SRS for brain metastases.

MATERIALS/METHODS

Patients with colorectal primary cancer who underwent SRS for brain metastases between 1989 and 2021 were retrospectively reviewed from a single institutional IRB-approved database. The primary endpoint was local failure (LF) and secondary endpoint was overall survival (OS). LF was estimated using the Cumulative Incidence Function with death as a competing risk. Survival analysis was performed using the Kaplan-Meier Method. Predictors of cumulative incidence of LF were assessed using competing risk regression.

RESULTS

The study population comprised of 109 patients with primary colorectal adenocarcinoma with 207 brain metastases. The median follow-up was 5.2 months (range: 0.4-124 months) and median OS was 5.8 months (range: 0.5-71.2 months). Fifty-two patients (48%) were male and median Karnofsky Performance Status at the time of treatment was 80 (range: 40-100). The median tumor diameter was 1.55 cm (range: 0.17-5.48 cm). The median prescription dose and number of fractions were 24 Gy (range: 11-36 Gy) and 1 fraction (range: 1-3 fractions), respectively. The cumulative incidence of LF at 3, 6, and 12 months was 9.7% (95% CI: 6.1-14%), 22% (95% CI: 16-28%), and 25% (95% CI: 20-31%), respectively. Overall survival at 3, 6, and 12 months was 81% (95% CI: 76-87%), 49% (95% CI: 42-56%) and 24% (95% CI: 18-31%), respectively. On univariate analysis, age was a significant predictor (HR = 0.96, 95% CI: 0.94-0.98), p < 0.001) of LF. Tumor size (HR = 0.80, p = 0.13) and prescription dose (HR = 1.02, p = 0.54) did not predict for LF.

CONCLUSION

To our knowledge, this is the largest series of patients with brain metastases from colorectal primary cancer treated with SRS. Compared to historical data, LF and OS in our cohort of patients was favorable. Our data confirms relatively higher rates of LF when compared to brain metastases from other primary disease sites. Further studies are warranted to identify factors that predict for LF following SRS and to develop models that predict which patients with colorectal brain metastases may be at higher risk of failure.

Studies on the Effect of Platelet Inhibitors on Platelet Adhesion to Collagen and Collagen-Induced Human Platelet Activation

The effect of pyridoxal 5’-phosphate (PALP) and trifluoperazine (TFPZ), the calmodulin antagonist, on in vitro platelet adhesion to collagen and collagen-induced platelet activation was studied using platelet-rich-plasma (PRP) or washed platelets (WPL). Platelet aggregation and [14C]-5HT release induced by “threshold” or low concentrations of collagen (0.6 μg/ ml) in PRP were completely abolished by PALP (24 mM), TFPZ (250 μM) as well as indomethacin (10 μM). At higher concentrations of collagen (10–15 μg/ml) in PRP and WPL, the use of stirred and unstirred platelets treated with collagen enabled a distinction to be made between aggregation and adhesion- mediated release reaction. Platelet aggregation and the aggregation-mediated release reaction induced by these concentrations of collagen in stirred platelets were completely abolished by PALP, TFPZ and indomethacin although neither adhesion to collagen nor the adhesion-mediated release reaction of unstirred platelets was significantly affected by these inhibitors. Interestingly, both adhesion and the adhesion-mediated release reaction were abolished by concentrations of PALP 10–40 fold higher than those required to abolish aggregation. Collagen-induced platelet aggregation, but not platelet adhesion, was inhibited in resuspended platelets pretreated with PALP and NaBH4 indicating a separation in the membrane sites involved in aggregation and adhesion. The results further emphasize the distinction between adhesion and aggregation-mediated events with regards to collagen with the latter being more susceptible to inhibition by antiplatelet agents such as PALP and TFPZ.

Effect of Pyridoxal 5'-Phosphate (PALP) on Human Platelet Aggregation, Dense Granule Release and Thromboxane B2 Generation - Role of Schiff Base Formation

Pyridoxal 5’-phosphate (PALP) inhibited ADP, thrombin, adrenaline, PAF and AA induced aggregation and 14C-5HT release. Thromboxane B2 (TxB2) generation induced by all the above agents except AA was also inhibited indicating that PALP may be inhibiting AA release via phospholipase A2 activation rather than AA metabolism. PALP inhibited ristocetin induced aggegation in PRP and agglutination in formaldehyde-treated washed platelets (FWP). Inhibition of ADP, adrenaline, PAF and AA-induced aggregation and 14C-5HT release by PALP was found in resuspended platelets pretreated with PALP and sodium borohydride suggesting that inhibition was mediated by Schiff base formation with platelet surface amino groups.

Irreversible fixation of PALP to the platelet membrane by borohydride reduction also inhibited thrombin induced 14C-5HT release and TxB2 generation but not thrombin induced primary aggregation or ristocetin induced agglutination in FWP. This suggests that PALP may interact with specific glycoproteins on the platelet membrane involved in ADP, adrenaline and PAF induced primary aggregation and that PALP could be inhibiting ristocetin induced agglutination by direct interaction with ristocetin or FVIII RCoF.

Mobilization of manganese by basalt associated Mn(II)-oxidizing bacteria from the Indian Ridge System

The Indian Ridge System basalt bearing Mn-oxide coatings had todorokite as the major and birnesite as the minor mineral. We posit that microorganisms associated with these basalts participate in the oxidation of Mn and contribute to mineral deposition. We also hypothesized that, the Mn-oxidizing microbes may respond reversibly to pulses of fresh organic carbon introduced into the water column by mobilizing the Mn in Mn-oxides. To test these two hypotheses, we enumerated the number of Mn-oxidizers and -reducers and carried out studies on the mobilization of Mn by microbial communities associated with basalt. In medium containing 100 μM Mn(2+), 10(3) colony forming units (CFU) were recovered with undetectable number of reducers on Mn-oxide amended medium, suggesting that the community was more oxidative. Experiments were then conducted with basalt fragments at 4±2 °C in the presence 'G(+)' and absence 'G(-)' of glucose (0.1%). Controls included set-ups, some of which were poisoned with 15 mM azide and the others of which were heat-killed. The mobilization of Mn in the presence of glucose was 1.76 μg g(-1) d(-1) and in the absence, it was 0.17 μg g(-1) d(-1) after 150 d. Mn mobilization with and without added glucose was 13 and 4 times greater than the corresponding azide treated controls. However, rates in 'G(+)' were 16 times and 'G(-)' 24 times more than the respective heat killed controls. The corresponding total counts in the presence of added glucose increased from 1.63×10(6) to 6.71×10(7) cells g(-1) and from 1.41×10(7) to 3.52×10(7) cells g(-1) in its absence. Thus, the addition of glucose as a proxy for organic carbon changed the community's response from Mn(II)-oxidizing to Mn(IV)-reducing activity. The results confirm the participation of Mn oxidizing bacteria in the mobilization of Mn. Identification of culturable bacteria by 16S rRNA gene analysis showed taxonomic affiliations to Bacillus, Exiguobacterium, Staphylococcus, Brevibacterium and Alcanivorax sp.

Diversity of bacteria and archaea from a landfill in Chandigarh, India as revealed by culture-dependent and culture-independent molecular approaches

The bacterial community structure of a municipal landfill in Chandigarh, India was analysed by culture-dependent as well as culture-independent molecular approaches, and archaeal structure by the latter method. Samples were collected in two phases from the surface and a depth of 0.91 m in June, 2004 and from 0.91 m, 1.52 m and 1.68 m in May, 2005. After serial dilutions, samples were plated onto tryptic soy agar (TSA), plate count agar (PCA), tryptic soy broth agar (TSBA) and TSBA100 (TSBA diluted 100 times and solidified with agarose), and incubated aerobically at 30°C. The number of bacteria (CFU) on different media ranged between 9.4×10⁵g⁻¹ (on PCA) and 1.9×10⁷g⁻¹ (on TSA) (wet weight). The numbers of bacteria enumerated from plates incubated anaerobically (anaerobic agar and reinforced clostridial agar) were 2.1×10⁷and 1.7×10⁶g⁻¹, respectively. Of the 468 isolated and purified bacteria (183 in the first phase and 285 in the second phase), 135 were characterised using phenotypic characteristics as well as 16S rRNA gene sequence analysis. It was found that members of the phylum Firmicutes were overwhelmingly predominant (86.6%) in the landfill, followed by Actinobacteria (9.6%) and Proteobacteria (3.7%). Among the Firmicutes, at least 17 species from the single genus Bacillus were the most abundant inhabitants of the landfill. Detailed polyphasic characterisation of many of these isolates led to the discovery of a novel genus Paenisporosarcina (and the species P. quisquiliarum), a novel species of Microbacterium, M. immunditiarum, and reclassification of Sporosarcina macmurdoensis, Pelagibacillus goriensis, Bacillus silvestris, Bacillus insolitus, Bacillus psychrotolerans and Bacillus psychrodurans. Culture-independent analysis of two 16S rRNA gene libraries also revealed that the phylum Firmicutes was the predominant group in this community. The diversity of Archaea was found to be limited mainly to members of two orders: Methanosarcinales and Methanomicrobiales of the phylum Euryarchaeota. When these results were compared to those reported earlier on similar studies, it was found that irrespective of differences in composition of municipal solid waste (especially compostable organic matter and paper) and climate, the members of bacterial and archaeal communities in landfills of many countries remained broadly similar.

Vibrio plantisponsor sp. nov., a diazotrophic bacterium isolated from a mangrove associated wild rice (Porteresia coarctata Tateoka)

Two Gram negative, facultatively anaerobic, halophilic, motile, slightly curved rod-shaped bacterial strains MSSRF60(T) and MSSRF64 were isolated from the roots of a mangrove-associated wild rice collected in the Pichavaram mangroves, India. These strains possess the key functional nitrogenase gene nifH. Phylogenetic analysis based on the 16S rRNA, recA, gapA, mreB, gyrB and pyrH, gene sequences revealed that strains MSSRF60(T) and MSSRF64 belong to the genus Vibrio, and had the highest sequence similarity with the type strains of Vibrio diazotrophicus LMG 7893(T) (99.7, 94.8, 98.5, 97.9, 94.0 and 90.7%, respectively), Vibrio areninigrae J74(T) (98.2, 87.5, 91.5, 88.9, 86.5 and 84.6% respectively) and Vibrio hispanicus LMG 13240(T) (97.8, 87.1, 91.7, 89.8, 84.1 and 81.9%, respectively). The fatty acid composition too confirmed the affiliation of strains MSSRF60(T) and MSSRF64 to the genus Vibrio. These strains can be differentiated from the most closely related Vibrio species by several phenotypic traits. The DNA G+C content of strain MSSRF60(T) was 41.8mol%. Based on phenotypic, chemotaxonomic, genotypic (multilocus sequence analysis using five genes and genomic fingerprinting using BOX-PCR) and DNA-DNA hybridization analyses, strains MSSRF60(T) and MSSRF64 represent a novel species of the genus Vibrio, for which the name Vibrio plantipsonsor sp. nov. is proposed. The type strain is MSSRF60(T) (=DSM 21026(T)=LMG 24470(T)=CAIM 1392(T)).

Psychrobacillus gen. nov. and proposal for reclassification of Bacillus insolitus Larkin & Stokes, 1967, B. psychrotolerans Abd-El Rahman et al., 2002 and B. psychrodurans Abd-El Rahman et al., 2002 as Psychrobacillus insolitus comb. nov., Psychrobacillus psychrotolerans comb. nov. and Psychrobacillus psychrodurans comb. nov

The taxonomic status of three Bacillus species, Bacillus insolitus, B. psychrodurans and B. psychrotolerans was reexamined using a polyphasic approach. In our analysis, these three Bacillus species formed a cluster separate from other members of Bacillus rRNA group 2 [5] and from Bacillus sensu stricto. These three species shared high 16S rRNA gene sequence similarities between them (97.8-99.7%) and showed closest sequence similarity (95.3-96.3%) to Paenisporosarcina quisquiliarum gen. nov., sp. nov. [18]. Sequence similarities with other related genera ranged between 90.9% and 94.5%. Phylogenetic coherence of the three species was supported by phenotypic characteristics, such as growth at low temperatures, negative oxidation and assimilation of many carbohydrates, MK8 as the major isoprenoid quinine and broadly similar polar lipid profiles. All three species had a similar peptidoglycan type of the variation A4β and similar genomic G+C contents (35.7-36.6 mol% [1]). Genomic relatedness among them was shown to be less than 70% and justified their separate species status [1]. These three species could be differentiated from each other and from related taxa on the basis of phenotypic, including chemotaxonomic, characteristics and ribotype patterns. On the basis of our analysis, we propose a new genus Psychrobacillus gen. nov. and to transfer B. insolitus, B. psychrodurans and B. psychrotolerans to the new genus as Psychrobacillus insolitus comb. nov. (type species of the genus; type strain W16B(T)=DSM 5(T)), P. psychrodurans comb. nov. (type strain 68E3(T)=DSM 11713(T)) and P. psychrotolerans comb. nov. (type strain 3H1(T)=DSM 11706(T)).

Fontibacillus aquaticus gen. nov., sp. nov., isolated from a warm spring

A novel facultatively anaerobic strain, designated GPTSA 19(T), was isolated from a warm spring and characterized using a polyphasic approach. The strain behaved as Gram-negative in the Gram staining procedure but showed a Gram-positive reaction in the aminopeptidase test. The novel strain was a mesophilic rod with ellipsoidal endospores. On the basis of 16S rRNA gene sequence analysis, the strain showed closest similarity (96.0 %) with Paenibacillus motobuensis MC10(T). The gene sequence similarity of the novel strain with other species of the genus Paenibacillus was <95.8 %. The novel strain also had PAEN 515F and 682F signature sequence stretches in the 16S rRNA gene that are usually found in most species of the genus Paenibacillus. The strain possessed anteiso-C(15 : 0) as the major fatty acid and MK-7 as the predominant menaquinone. Polar lipids included diphosphatidylglycerol (DPG), phosphatidylglycerol (PG), phosphatidylethanolamine (PE), six unknown phospholipids (PLs), one aminophospholipid (PN), three glycolipids (GLs), two aminolipids (ALs), one aminophosphoglycolipid (APGL) and three unknown lipids (ULs). The polar lipid profile of the novel strain, especially as regards ALs, GLs and PLs, distinguished it from the recognized type species of the genus Paenibacillus, Paenibacillus polymyxa, as well as from its closest relative P. motobuensis. Based on phenotypic and chemotaxonomic characteristics and analysis of the 16S rRNA gene sequence, the new strain merits the rank of a novel genus for which the name Fontibacillus gen. nov. is proposed. The type species of the new genus is Fontibacillus aquaticus gen. nov., sp. nov. with the type strain GPTSA 19(T) (=MTCC 7155(T)=DSM 17643(T)).

Description of Paenisporosarcina quisquiliarum gen. nov., sp. nov., and reclassification of Sporosarcina macmurdoensis Reddy et al. 2003 as Paenisporosarcina macmurdoensis comb. nov

In the course of a study of the prokaryotic diversity of a landfill site in Chandigarh, India, a strain designated SK 55(T) was isolated and characterized using a polyphasic approach. Its 16S rRNA gene sequence showed closest similarity (98.3 %) to that of Sporosarcina macmurdoensis CMS 21w(T). The sequence similarity to strains of other hitherto described species of Sporosarcina was less than 95.5 %. Strain SK 55(T) contains peptidoglycan of the A4alpha type (l-Lys-d-Asp), MK-8 and MK-7 as the major menaquinones and iso-C(15 : 0) as the major fatty acid. Strain SK 55(T), Sporosarcina macmurdoensis and Sporosarcina ureae, the type species of the genus, had some polar lipids in common (diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, a phospholipid and an unknown lipid). However, an aminolipid, an aminophospholipid and an unknown lipid found in the former two organisms are similar, though not identical, but quite different from the profile of S. ureae. The genomic DNA G+C contents of strain SK 55(T) (46.0 mol%) and S. macmurdoensis CMS 21w(T) (44.0 mol%) are higher than those reported for the majority of species of Sporosarcina (36-42 mol%). As revealed by 16S rRNA gene sequence analysis, strain SK 55(T) and S. macmurdoensis CMS 21w(T) form a clade which is distinct from the clade occupied by other species of Sporosarcina. On the basis of phenotypic characteristics including chemotaxonomic data and analysis of the 16S rRNA gene sequence, we conclude that strain SK 55(T) should be considered as a member of a novel genus and species, for which the name Paenisporosarcina quisquiliarum gen. nov., sp. nov. is proposed. The type strain of Paenisporosarcina quisquiliarum is SK 55(T) (=MTCC7604(T) =JCM 14041(T)). S. macmurdoensis CMS 21w(T) shows more similarity in its 16S rRNA gene sequence (98.3 %), DNA G+C content and polar lipid profile to strain SK 55(T) than to S. ureae DSM 2281(T). Phylogenetically, it forms a coherent cluster with strain SK 55(T) which is separate from the Sporosarcina cluster. Moreover, iso-C(15 : 0), anteiso-C(15 : 0) and C(16 : 1)omega7c alcohol are the three major fatty acids in both S. macmurdoensis CMS 21w(T) and SK 55(T). All these data suggest that S. macmurdoensis should be a member of the genus Paenisporosarcina. However, S. macmurdoensis can be differentiated from SK 55(T) in several physiological and biochemical characteristics, especially in the patterns of oxidation and acid production from carbohydrates. The genomic relatedness of S. macmurdoensis CMS 21w(T) and strain SK 55(T) was also very low (18.0 %). It is therefore logical to transfer Sporosarcina macmurdoensis to the newly created genus as Paenisporosarcina macmurdoensis comb. nov. The type strain is CMS 21w(T) (=MTCC4670(T) =DSM 15428(T)).

Phase II study of weekly administration of docetaxel (D) in combination with the epidermal growth factor receptor (EGFR) inhibitor erlotinib (E) in metastatic breast cancer (MBC)

Abstract #3124

Background: Single agent weekly docetaxel (D) is an active agent in the treatment of metastatic breast cancer (MBC) with response rates of 29% - 53%. Erlotinib (OSI-774, Tarceva®) is a tyrosine kinase inhibitor directed against EGFR, which is overexpressed in 30-40% of breast cancers, making EGFR an attractive treatment target. This study was designed to assess the combination of D and E in previously untreated recurrent and/or MBC.&#x2028; Methods: Adult patients with histologically confirmed MBC without prior chemotherapy for recurrence or metastases were eligible. Treatment plan was: D (initially 35 mg/m2 intravenous infusion weekly x 3 every 4 weeks) and E 150 mg orally daily uninterrupted. In patients with responding or stable disease, E was continued in 4 week cycles following a minimum of 6 cycles of D and E. Estimates of overall survival (OS) and progression free survival (PFS) were made by Kaplan-Meier method and the difference between groups by log-rank test. Tumor EGFR expression by immunohistochemisty and ER/PR was correlated with OS and PFS.&#x2028; Results: 39 female pts were enrolled between 12/02 and 8/06. The median age was 51 yrs (range 28-78). The median number of cycles of D and E received was 4 (range 1-26) and of E following D and E was 11 (range 2-18). EGFR, ER/PR and Her-2/neu status was determined on 35/39 patients. EGFR: 23 positive, 12 negative. ER/PR: 25 positive, 10 negative. Her-2/neu: 2 positive, 33 negative. Ten pts. were not evaluable for survival or response due to toxicity occurring within the first cycle. Best responses (n=29) ; PR 11(39%), SD 4 (14%), PD 13 (45%), and clinical benefit (PR+SD) 15 (54%). Median PFS was 8 mos (95% CI: 4.4-12.2). PFS for EGFR negative tumors appeared better than EGFR positive tumors (12 mos PFS 33% vs. 23%) but was not significant (p = 0.53). There was no difference in OS between these groups (p=0.38). PFS and OS for ER/PR positive pts was significantly higher than ER/PR negative pts 6 mos PFS 67% vs. 25% (p= 0.009) and 2 yr OS 53.9% vs. 12.5% (p=0.015). , All patients were included for toxicity assessment (n-39). The first 26 pts received planned D dose of 35mg/m2. Because of non-hematologic toxicity, trial was subsequently modified to start D at 25 mg/m2. Grade 3 or 4 Leukopenia was seen in 15% pts. Principal non-hematologic grade 3-4 toxicities included anorexia, diarrhea, and fatigue (18% pts).&#x2028; Conclusions: Combination therapy for advanced breast cancer with docetaxel and erlotinib shows promising activity with favorable response compared with other studies. There was no significant association with EGFR expression and PFS, however this combination is more favorable for ER positive patients. Randomized trials for ER positive disease is warranted to further investigate the efficacy of this combination compared to single agent docetaxel.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 3124.

Phase I trial of combination becatecarin and oxaliplatin in patients with advanced solid tumors

2561

Background: Becatecarin (rebeccamycin analogue-RA) is an anti-tumor antibiotic with inhibitory activity against both topoisomerase II and I as well as DNA intercalating properties. We performed a phase I trial to a) determine the maximum tolerated dose (MTD) of RA in combination with oxaliplatin; b) determine the dose limiting toxicities (DLT) (c) obtain data on pharmacokinetics and (d) observe for any antitumor activity. Methods: Eligibility criteria included patients with advanced solid tumors refractory to standard therapy; performance status 0–2; adequate hematologic, renal and liver function. Patients were treated with RA as a 1 hour infusion daily x 5 and oxaliplatin on day 5 only, after RA infusion. Treatment was repeated q 21 days. The following dose levels were evaluated: Dose level 1: RA 80 mg/m2/d and oxaliplatin 90 mg/m2; Dose level 2: RA 80 mg/m2/d and oxaliplatin 130 mg/m2; Dose level 3: RA 110 mg/m2/d and oxaliplatin 130 mg/m2. Results: A total of 15 evaluable patients were enrolled. Median age was 56 (8 male, 7 female). A variety of tumor types were enrolled. A total of 56 cycles were administered. DLT occurred at a dose of RA at 110 mg/m2/d x 5 days and oxaliplatin at 130 mg/m2 and consisted of grade 3 hypophosphatemia and grade 4 atrial fibrillation. At this dose level 2 of 3 enrolled patients also developed grade 3 neutropenia. The MTD and recommended phase II dose was RA at 80 mg/m2/daily x 5 along with oxaliplatin 130 mg/m2 day 5 q 21 days. Three confirmed partial responses were observed in patients with hepatocellular, gallbladder and esophageal cancers. Six patients experienced stable disease. Conclusions: At the MTD combination RA and oxaliplatin is well tolerated and given the response rate and stable diseases observed, phase II studies are recommended. Supported by Grants U01 CA62502, MO1-RR-00080, K23 CA109348–01 from the National Institutes of Health.

No significant financial relationships to disclose.

Bosutinib (SKI-606), a dual Src/Abl tyrosine kinase inhibitor: Preliminary results from a phase 1 study in patients with advanced malignant solid tumors

3552

Background: Bosutinib (SKI-606) is a potent, low molecular weight, orally active, competitive inhibitor of both Src and Abl tyrosine kinases. Elevations of Src kinase activity occur in a variety of human tumor types and are correlated with aggressiveness. We conducted a phase 1 study in patients (pts) with advanced solid tumors to assess tolerability, safety, pharmacokinetics (PK), and preliminary antitumor activity of bosutinib. Methods: Patients in cohorts of 3–6 received 50, 100, 200, 300, 400, 500 or 600 mg bosutinib orally on study day 1 and then once daily beginning on day 3. Timed blood samples were collected on days 1–3, 15 and 16 for PK analysis. Tumor assessments (modified RECIST criteria) were made at baseline and the end of every third cycle (21 days/cycle). Collection of tissue samples for analysis of Src biomarkers was optional. Results: Preliminary data are presented for 51 pts (median 57 years, 57% women). Three pts who received 600 mg bosutinib/day had drug-related dose-limiting toxicity of grade 3 diarrhea (2 pts) and grade 3 rash (1 pt). Gastrointestinal (GI) toxicity was reported among 6 pts in the 500-mg maximum tolerated dose (MTD) lead-in cohort so that 400 mg was selected as the MTD. Drug-related adverse events (AEs), any grade, occurring in =25% of pts were nausea (67%), diarrhea (55%), anorexia (45%), vomiting (43%), asthenia (41%). The only grade 3 drug-related AE occurring in =5% of pts was diarrhea (14%). After oral administration, bosutinib exposure increased in a dose-dependent manner. Multiple-dose exposure was nearly 2- to 3-fold higher than single-dose exposure. Mean elimination half-life was approximately 17 to 21 hours, supporting a once-daily dosing regimen. Six pts had stable disease >15 weeks (2 pts each with breast, colorectal cancer, non-small cell lung cancer [NSCLC]) and 1 pt had stable disease >52 weeks (pancreatic cancer). Conclusions: Bosutinib was generally well tolerated with predominantly gastrointestinal AEs. Accrual and evaluation of an expanded cohort restricted to patients with colorectal, pancreatic, and NSCLC tumors is ongoing. The patient with pancreatic cancer has had stable disease >52 weeks.

No significant financial relationships to disclose.

Phase I trial of daily lenalidomide and docetaxel given every three weeks in patients with advanced solid tumors

3570

Background: Lenalidomide is a potent anti-angiogenic and immune modulating agent. This phase I trial of docetaxel and lenalidomide was undertaken to evaluate the maximal tolerated dose (MTD), dose-limiting toxicity (DLT), and secondarily, any tumor response for this novel combination. Methods: Patients with advanced solid tumors with adequate organ function were eligible. Lenalidomide was given orally days 1–14, and docetaxel was administered intravenously on day 1 of each 21-day cycle. DLT was defined as grade 3 or higher non-hematologic toxicity, grade 4 neutropenia with fever, and grade 4 anemia or thrombocytopenia. Results: Nineteen patients, 14 male and 5 female, with tumor types including prostate (7), sarcoma (3), head and neck (2), pancreatic, colon, melanoma, adenocarcinoma of unknown primary, gastric, bladder, and GIST have been enrolled. ECOG performance status was zero (10 patients) or one (9 patients). The median age was 59 years (range 35 to 86). Fourteen patients had zero or one prior treatment regimens (range 0 to 6). A total of 64 cycles have been administered (range 1 to 12). In the first nine evaluable patients, eight (89%) had grade 3 or 4 neutropenia. Docetaxel 75 mg/m2 given every 3 weeks with lenalidomide 5 mg on days 1–14 exceeded the MTD due to one grade 3 nausea/vomiting and one grade 4 neutropenia with fever. After the addition of pegfilgrastim on day 2, there has not been any neutropenia in the subsequent seven evaluable patients. Other grade 3 and 4 toxicities included leukopenia (31%), lymphopenia (19%), as well as nausea, vomiting, fatigue, anemia, infection, hyponatremia, and hypokalemia (6% each). Seven patients (44%) have had stable disease (range 3 to 12 cycles). One prostate cancer patient experienced a >95% reduction of PSA. Enrollment is ongoing and the current dose level is docetaxel 75 mg/m2, lenalidomide 10 mg days 1–14, and pegfilgrastim on day 2. Conclusions: The toxicity evaluation is ongoing. This trial will provide the MTD of docetaxel 75 mg/m2 given every 3 weeks with lenalidomide on days 1–14 in combination with pegfilgrastim support to avoid neutropenia.

No significant financial relationships to disclose.

Rhodococcus kroppenstedtii sp. nov., a novel actinobacterium isolated from a cold desert of the Himalayas, India

The taxonomic position of an actinomycete, strain K07-23T, isolated from a cold desert of the Himalayas, India, was established by a polyphasic approach. The strain exhibited phenotypic characters that were typical of the genus Rhodococcus. 16S rRNA gene sequence (1467 bases) comparisons confirmed that strain K07-23T belongs to the genus Rhodococcus. 16S rRNA sequence similarity studies showed that the isolate is very closely related to Nocardia corynebacterioides DSM 20151T (98.6 %), which has been recently reclassified as Rhodococcus corynebacterioides. It showed 94.4-96.6 % sequence similarity with other species of the genus Rhodococcus. However, genomic relatedness between strain K07-23T and R. corynebacterioides as revealed by DNA-DNA hybridization was low (62 %). Based on polyphasic analysis, strain K07-23T could be clearly distinguished from other species. It is proposed that strain K07-23T (=MTCC 6634T=DSM 44908T=JCM 13011T) represents a novel species of Rhodococcus, Rhodococcus kroppenstedtii sp. nov.

Toxicity and outcome data in a phase II study of weekly docetaxel in combination with erlotinib in recurrent and/or metastatic breast cancer (MBC)

10623

Background: Single agent weekly docetaxel (D) is an active agent in the treatment of MBC with response rates of 29% - 53%. Erlotinib (OSI-774, Tarceva) is a tyrosine kinase inhibitor directed against the epidermal growth factor receptor (EGFR), and is overexpressed in 30–40% of breast cancers. EGFR inhibition by erlotinib (E) and its possible modulation of growth factor synthesis by breast cancer (BC) cells is an attractive treatment target. This study was designed to assess the combination of D and E in previously untreated recurrent &/or MBC. Methods: Adult patients (pts) with histologically confirmed BC without prior chemotherapy for recurrence or metastases were eligible. Treatment plan was: D [35 mg/m2 iv infusion weekly x 3 q4wks] and E 150 mg/d uninterrupted (D+E). E was to be continued in 4 week cycles after maximum tumor response or disease stabilization [following a minimum of 6 cycles of D+E]. The overall survival (OS) was estimated by Kaplan-Meier method. Results: 31of 40 planned female pts were enrolled between 12/02 and 9/05. Median age 52 years, range: 29–79. The median number of cycles of D +E received was 4, (range 1–9) and of E following D+E was 4 (range 1–29). The first 26 pts received planned D dose of 35mg/m2. Because of non-hematologic toxicity, trial was subsequently modified to start D at 30mg/m2.11/31 (36%) were not evaluable due to toxicity. Hematologic grade 3 or 4 toxicity was seen in 45% cases. Principal non-hematologic grade 3–4 toxicities included nausea, diarrhea, and constitutional symptoms seen in 30% of the pts. 4/9 pts receiving E after D+E experienced hematologic, hepatic, constitiutional, and eye (1 each) grade 3 toxicity only. Best clinical response in the 20 evaluable pts included; PR 11(55%), SD 7 (35%), PD 2 (10%). OS (n = 31) was 71% at 12mos, 42% at 24 mos with median OS 23 mos. Conclusions: Combination therapy of advanced breast cancer with Docetaxel and Erlotinib showed promising activity with favorable response compared to other studies. The combination is associated with moderate to severe hematological and non-hematological toxicities. Randomized trials are warranted to further investivate the efficacy of this combination compared to single agent Docetaxel. (Support: Sanofi-Aventis & Genentech.)

[Table: see text]

Kitasatospora sampliensis sp. nov., a novel actinobacterium isolated from soil of a sugar-cane field in India

Polyphasic characterization of an actinomycete strain VT-36T isolated from a sugar-cane field soil sample collected in Punjab State, India, revealed that the strain belongs to the genus Kitasatospora. The strain's chemotaxonomic characters and G+C content of DNA (76·5 mol%) were typical of members of the genus. Analysis of the 16S rRNA gene sequence supported the generic affiliation of the strain and showed that its closest phylogenetic relative was Kitasatospora putterlickiae F18-98T (=DSM 44665T) (98·3 % 16S rRNA gene sequence similarity). The similarities with type strains of all other Kitasatospora species were in the range 95·1–97·0 %. The results of DNA–DNA hybridization showed 54 % relatedness of the isolate and K. putterlickiae F18-98T. Based on the above data and the phenotypic differences from K. putterlickiae and other Kitasatospora species, it is proposed that the isolate should be classified as the type strain of a novel species, Kitasatospora sampliensis sp. nov., with strain VT-36T (=MTCC 6546T=DSM 44898T=JCM 13010T) as the type strain.

Actinoalloteichus spitiensis sp. nov., a novel actinobacterium isolated from a cold desert of the Indian Himalayas

An actinobacterial strain, RMV-1378T, isolated from a cold desert of the Indian Himalayas, was subjected to polyphasic taxonomic characterization. The strain formed branching, non-fragmenting vegetative hyphae and did not produce diffusible pigments. Neither aerial mycelium nor spore formation was observed. The G+C content of the DNA was 72.0 mol%. The strain had chemotaxonomic characteristics typical of the genus Actinoalloteichus and was closely related (99.3 % 16S rRNA gene sequence similarity) to Actinoalloteichus cyanogriseus, currently the only Actinoalloteichus species with a validly published name. However, the results of DNA-DNA hybridization experiments showed 51.9 % relatedness with the type strain of A. cyanogriseus. On the basis of the above data and the physiological and biochemical distinctiveness of RMV-1378T (=MTCC 6194T=JCM 12472T=DSM 44848T), this strain should be classified as the type strain of a novel species of Actinoalloteichus, for which the name Actinoalloteichus spitiensis sp. nov. is proposed.

Paenibacillus assamensis sp. nov., a novel bacterium isolated from a warm spring in Assam, India

A polyphasic approach was used to characterize a bacterium, GPTSA 11(T), isolated from a warm spring located in a reserve forest in Assam, India. The cells are Gram-variable, strictly aerobic, sporulating motile rods. The major fatty acids of the strain are C(15 : 0) anteiso (48.42 %), C(16 : 0) iso (11.59 %), C(16 : 1)omega11c (6.16 %), C(15 : 0) iso (6.03 %), C(17 : 0) anteiso (5.68 %) and C(16 : 1)omega7c alcohol (5.01 %). The presence of the fatty acid C(16 : 1)omega7c alcohol distinguishes this strain from other closely related species of the genus Paenibacillus. The strain contains MK-7 as the diagnostic menaquinone. The G+C content of the genomic DNA is 41.2 mol%. Analysis of the 16S rRNA gene sequence (1466 nt) revealed the presence of signature sequences PAEN 515F (5'-GAGTAACTGCTCTCGGAATGACGGTACTTGAGAAGAAAGCCCC-3') and PAEN 862F (5'-TCGATACCCTTGGTGCCGAAGT-3'), which were found in the species of the genus Paenibacillus surveyed by Shida et al. [Shida, O., Takagi, H., Kadowaki, K., Nakamura, L. K. & Komagata, K. (1997). Int J Syst Bacteriol 47, 289-298]. The sequence shows closest similarity (95.85 %) to that of Paenibacillus apiarius, followed by Paenibacillus alvei (94.34 %), Paenibacillus cineris (93.87 %), Paenibacillus favisporus (93.80 %), Paenibacillus chibensis (93.47 %) and Paenibacillus azoreducens (93.40 %). Biochemical, physiological, chemotaxonomic and phylogenetic analyses justify placement of the strain in the genus Paenibacillus but not within any existing species. It should, therefore, be considered as representing a novel species, for which the name Paenibacillus assamensis sp. nov. is proposed. The type strain is GPTSA 11T (=MTCC 6934T=JCM 13186T).

Aquimonas voraii gen. nov., sp. nov., a novel gammaproteobacterium isolated from a warm spring of Assam, India

A bacterial strain designated GPTSA 20(T), which was isolated from a warm spring in Assam, India, was characterized by using a polyphasic approach. The cells were Gram-negative, aerobic rods, which could not utilize or produce acid from most of the carbohydrates tested. The predominant fatty acids were C(15:0) iso (25.04%), C(17:1) iso omega9c (19.28%), C(16:0) iso (17.73%) and C(11:0) iso 3-OH (9.34%). The G+C content was 75 mol%. From 16S rRNA gene sequence analysis (1433 nucleotides, continuous stretch), it was confirmed that strain GPTSA 20(T) belonged to the class 'Gammaproteobacteria'. The closest 16S rRNA gene sequence similarity found (98.2%) was with an uncultured bacterium clone, NB-03 (accession no. AB117707), from an autotrophic nitrifying biofilm. Among culturable bacteria, the closest sequence similarities were with Fulvimonas soli (93.0%), Silanimonas lenta (92.8%), Thermomonas hydrothermalis (92.4%), Frateuria aurantia (91.9%), Rhodanobacter lindaniclasticus (91.9%), Thermomonas haemolytica (91.9%) and Pseudoxanthomonas taiwanensis (91.8%); similarities of less than 91.8% were obtained with other members of the class 'Gammaproteobacteria'. From the biochemical, physiological, chemotaxonomic and phylogenetic analysis, it was clear that strain GPTSA 20(T) was quite different from members of known genera of the class 'Gammaproteobacteria'. Therefore, it is proposed that strain GPTSA 20(T) represents a novel species within a new genus, with the name Aquimonas voraii gen. nov., sp. nov. The type strain is GPTSA 20(T) (=MTCC 6713(T)=JCM 12896(T)).

Epidemiology of cancer of the cervix: global and national perspective

Cancer of the uterine cervix is one of the leading causes of cancer death among women worldwide. The estimated new cancer cervix cases per year is 500,000 of which 79% occur in the developing countries. Cancer cervix occupies either the top rank or second among cancers in women in the developing countries, whereas in the affluent countries cancer cervix does not even find a place in the top 5 leading cancers in women. The truncated rate (TR) in the age group 35-64 years in Chennai, India, is even higher (99.1/100,000; 1982-95) than rate reported from Cali, Colombia (77.4/100,000, 1987-91). The cervical cancer burden in India alone is estimated as 100,000 in 2001 AD. The differential pattern of cervical cancer and the wide variation in incidence are possibly related to environmental differences. Aetiologic association and possible risk factors for cervical carcinoma have been extensively studied. The factors are: Sexual and reproductive factors, socio-economic factors (education and income), viruses e.g., herpes simplex virus (HSV), human papillomavirus (HPV), human immunodeficiency virus (HIV) in cervical carcinogenesis and other factors like smoking, diet, oral contraceptives, hormones, etc. The accumulated evidence suggests that cervical cancer is preventable and is highly suitable for primary prevention. Sexual hygiene, use of barrier contraceptives and ritual circumcision can undoubtedly reduce cervical cancer incidence. Education, cervical cancer screening of high risk groups and improvement in socio-economic status can reduce cervical cancer morbidity and mortality significantly.

Cervical cancer screening in Tamilnadu, India: a feasibility study of training the village health nurse

Uterine cervical cancer is the most common malignancy among females in developing countries, including India. The success of cervical cancer screening programs in North America and Western Europe has been the result of centralized cervical-cytology screening. This is not possible in the villages (n = 17,000) of Tamilnadu where 58 percent of females in rural areas are illiterate, health infrastructure is mediocre, and cervical cytology is unknown. The present study was undertaken to examine if the village health nurse (VHN) could be trained quickly to identify a cervical abnormality by visual inspection so that we could 'down stage' the cancer to earlier stages, more amenable to treatment. VHNs also would be trained to take an adequate Pap smear. A total of 101 VHNs were trained in batches and returned to their villages. Within two years, 6,459 eligible women in the study area were screened. The agreement between the gynecologists and the VHNs in identifying cancer among those with abnormal cervix was 95 percent, and 80 percent of the Pap smears taken by VHNs were adequate by WHO criteria, making the feasibility study highly successful.

Comparative endoscopic study of primary gastric lymphoma vs. gastric carcinoma

The endoscopic records of 56 patients with primary gastric lymphoma and 120 patients with gastric adenocarcinoma (matched for age and sex) were compared with respect to site, extent, and type of tumor by endoscopy and biopsy results. Diagnosis of lymphoma was suspected on the basis of gross endoscopic appearance in 30 patients with 96% sensitivity. The endoscopic findings that achieved statistical significance in favor of lymphoma were extensive disease involving whole stomach, proximal stomach involvement, extension of tumor into duodenum, and the presence of volcano crater-like ulcers on polypoid lesions. Endoscopic biopsies were positive for lymphoma in 92% patients. Immunoperoxidase staining for leucocyte common antigen was positive in all the 24 patients with lymphoma where it was performed. We conclude that lymphoid origin of the stomach tumor may be suspected in one-half of the cases of primary gastric lymphoma by gross endoscopic findings. Multiple endoscopic biopsies are safe and highly sensitive and specific in the diagnosis of primary gastric lymphoma.

Preoperative multimodal therapy for locally advanced non-inflammatory breast cancer

The present study is a comparison of two sequential groups of advanced locoregional (T3, T4) non-inflammatory breast cancers. The first group was of 164 cases treated between 1965 and 1975 who received radiotherapy followed by surgery (Group I). The second group was of 211 cases treated between 1976 and 1984, who received radiotherapy combined with multidrug chemotherapy followed by surgery (Group II). The 5 and 10 year disease-free survival in the two groups are 47.5% vs 60.6% (P less than 0.005) and at 10 years 35.9% vs 44.1% respectively (P less than 0.005). Tumour sterility in the resected breast was more than doubled in the chemotherapy group (18.9% vs 42.1%). The impact of the addition of chemotherapy on survival was seen only in the node-positive group, the 5-year disease-free survival in node-positive cases being 44.7% compared to 28.2% when chemotherapy was not used (P less than 0.007). Remote metastases at 5 years in node positive cases also showed a significantly lower rate in the CT + RT arm against the RT-only arm (36.4% vs 54.3%) (P less than 0.005). The results clearly demonstrate the advantage of a multimodality approach in the management of Stage III breast cancers.

Influence of nitric oxide on agonist-mediated calcium mobilization in platelets

Recent studies have characterized endothelium-derived relaxing factor as nitric oxide. It appears to exert its effect by elevating intracellular levels of cyclic GMP. In this study we confirm that nitric oxide is a potent inhibitor of agonist-induced irreversible aggregation. At the concentrations tested nitric oxide effectively blocked thrombin-stimulated mobilization of cytosolic-free calcium in Fura 2-loaded platelets. In addition, nitric oxide prevented the inositol 1,4,5-trisphosphate-stimulated calcium rise in cytosolic calcium in saponin-permeabilized Fura 2-loaded platelets. Similar to the action of adenylate cyclase stimulators, nitric oxide facilitated lowering of calcium levels raised by the action of agonists. The specific mechanism by which it exerts its effect on intracellular levels of calcium is not clear.

Radiation, pepleomycin and hyperthermia in the therapy of locally advanced squamous cell carcinomas of the buccal mucosa

Oral squamous cell carcinoma is the commonest male (29%) and the second commonest female (18%) malignancy in South India. At first attendance 93% of the tumours are stage T3 or T4. They are essentially locoregional, remote metastases being rare (0.75%). Radiotherapy alone yields a poor survival (19% 5 year NED). Radiopotentiation by chemical sensitizers and cytotoxic drugs has been attempted since 1960, the best results being obtained by a combination of irradiation and bleomycin. There was, however, persistent failure in about 40% of cases. The present three-armed trial attempted to improve the results of radiotherapy and bleomycin by the addition of hyperthermia. A total of 101 T3 and T4 buccal squamous cancers were entered in the trial over a period of nearly three years. Entry closed in August 1987 and the last case was evaluated in October 1987, hence only response data are available. Hyperthermia did not confer any benefit.

Extracellular Na+, but not Na+/H+ exchange, is necessary for receptor-mediated arachidonate release in platelets

The effect of extracellular Na+ removal and replacement with other cations on receptor-mediated arachidonate release in platelets was studied to investigate the role of Na+/H+ exchange in this process. Replacement with choline+, K+, N-methylglucamine+ (which abolished the thrombin-induced pHi rise) or Li+ (which allowed a normal thrombin-induced pHi rise) significantly decreased arachidonate release in response to all concentrations (threshold to supra-maximal) of thrombin and collagen. This inhibition was not reversed by NH4Cl (10 mM) addition, which raised the pHi in the absence of Na+, but, on the contrary, NH4Cl addition further decreased the extent of thrombin- and collagen-induced arachidonate release, as well as decreasing 'weak'-agonist (ADP, adrenaline)-induced release and granule secretion in platelet-rich plasma. No detectable pHi rises were seen with collagen (1-20 micrograms/ml) and ADP (10 microM) in bis-(carboxyethyl)carboxyfluorescein-loaded platelets. Inhibition of thrombin-induced pHi rises was seen with 0.5-5 microM-5-NN-ethylisopropylamiloride (EIPA), but at these concentrations EIPA had little effect on thrombin-induced arachidonate release. At higher concentrations such as those used in previous studies (20-50 microM), EIPA inhibited aggregation/release induced by collagen and ADP in Na+ buffer as well as in choline+ buffer (where there was no detectable exchanger activity), suggesting that these concentrations of EIPA exert 'non-specific' effects at the membrane level. The results suggest that (i) Na+/H+ exchange and pHi elevations are not only necessary, but are probably inhibitory, to receptor-mediated arachidonate release in platelets, (ii) inhibition of receptor-mediated release in the absence of Na+ is most likely due to the absent Na+ ion itself, and (iii) caution should be exercised in the use of compounds such as EIPA, which, apart from inhibiting the Na+/H+ exchanger, have other undesirable and misleading effects in platelets.

Receptor- and phorbol-ester-mediated redistribution of protein kinase C in human platelets. Evidence that aggregation promotes degradation of protein kinase C

Translocation of Ca2+/phospholipid-dependent protein kinase (PKC) activity from cytosolic to membrane fractions was assessed in washed human platelet suspensions. Phorbol myristate acetate (PMA) induced a rapid loss of PKC activity from the cytosolic compartment in stirred platelets, which was not accompanied by measurable increases in membrane-associated activity, but was paralleled by a decrease in total cellular enzyme activity (cytosol plus membrane). When platelet aggregation was prevented by not stirring, (i) cytosolic activity was decreased by PMA, (ii) significant and maintained (1-15 min with PMA) increases in membrane-bound PKC were detected, and (iii) the decline in total enzyme activity was markedly slower. In stirred platelets, total and specific inhibition of PMA-induced aggregation by a fibrinogen-derived peptide (RGDS, i.e. Arg-Gly-Asp-Ser) promoted maximal increases in membrane-associated PKC in the presence of PMA and completely prevented the loss in cellular activity. Thrombin and collagen both induced a decrease in cytosolic PKC and a loss of total activity, but a significant rise in membrane activity was seen only with collagen; ADP had no detectable effect on enzyme distribution. These results demonstrate an agonist-induced redistribution of PKC and indicate that platelet aggregation may play an important role in the proteolysis, and hence persistence, of membrane-associated PKC. This observation has implications for the potency and duration of PKC-mediated responses induced by agonists and exogenous PKC activators.

The fibrinogen-derived peptide (RGDS) prevents proteolytic degradation of protein kinase C in platelets by inhibiting platelet aggregation

The effects of the fibrinogen-derived tetrapeptide, Arg-Gly-Asp-Ser (RGDS), on platelet activation processes was studied. At concentrations of 100-300 microM, RGDS completely prevented platelet aggregation induced by all the common platelet agonists, 'weak' and 'strong'. In agreement with earlier views on the aggregation-dependency of weak agonist-induced thromboxane synthesis and 5-hydroxytryptamine (5HT) secretion, RGDS (100-300 microM) inhibited these events induced by ADP, adrenaline and low concentrations of thrombin and collagen but not that induced by high concentrations of thrombin and collagen. 5HT secretion induced by the protein kinase C (PKC) activator, phorbol 12-myristate 13-acetate (PMA), was also not affected by RGDS, but proteolytic degradation of the translocated membrane-bound enzyme in PMA-treated platelets, due to the actions of the Ca2+-dependent protease (Ca-DP), was completely prevented such that in the presence of RGDS, sustained increases in membrane-bound PKC activity were observed. PMA alone caused only transient increases in membrane-bound PKC. This effect of RGDS was similar to the effect of E64-d, a recently described inhibitor of Ca-DP in platelets, or the effects seen with PMA in unstirred non-aggregating platelets. It is concluded that RGDS inhibits the actions of Ca-DP in platelets via inhibition of aggregation.

Effect of phorbol ester treatment on receptor-mediated versus G-protein-activator-mediated responses in platelets. Evidence for a two-site action of phorbol ester at the level of G-protein function

In platelets, and in several other cell systems, pre-treatment with protein kinase C activators such as phorbol 12-myristate 13-acetate (PMA) results in the inhibition of receptor-mediated responses, suggesting that protein kinase C may play an important role in the termination of signal transduction. In the present study, we have attempted to locate the site of action of phorbol ester by comparing thrombin-induced (i.e. receptor-mediated) platelet activation with that induced by guanosine 5'-[gamma-thio]triphosphate (GTP[S]) and NaF, two agents which by-pass the receptor and initiate platelet responses by directly modulating G-protein function. After a 10 s pre-treatment with PMA (16 nM), dense-granule secretion induced by thrombin (0.2 unit/ml), GTP[S] (40 microM) and NaF (30 mM) was potentiated, resulting in a greater than additive response to agent plus PMA. However, after a 5 min pre-treatment, thrombin-induced secretion alone was inhibited, whereas PMA plus GTP[S]/NaF-induced release remained greater than additive. [32P]Phosphatidate formation in response to all three agents, in contrast, was inhibited by 50-70% in PMA (5 min)-treated platelets. That secretion induced by these agents is a protein kinase C-dependent event was demonstrable by using staurosporine, a protein kinase C inhibitor which at concentrations of 1-10 nM inhibited (70-90%) PMA-induced as well as thrombin- and NaF-induced secretion and protein phosphorylation. In membranes from PMA-treated platelets, thrombin-stimulated GTPase activity was significantly enhanced compared with that in untreated membranes (59% versus 82% increase over basal activity). The results suggest that inhibition of receptor-mediated responses by PMA may be directed towards two sites relating to G-protein activation: (i) receptor-stimulated GTPase activity and (ii) G-protein-phospholipase C coupling. Furthermore, the lack of inhibition of NaF- and GTP[S]-induced secretion by PMA suggests that different mechanisms may be involved in thrombin-induced and G-protein-activator-induced secretion.

Na+/H+ exchange is not necessary for protein kinase C-mediated effects in platelets

The role of Na+/H+ exchange in protein kinase C-mediated effects in platelets was investigated by studying the effect of removal of extracellular Na+ ([Na+]e) on the different responses induced by phorbol 12-myristate 13-acetate (PMA) and 1,2-dioctanoylglycerol (diC8). None of the responses studied, namely, protein phosphorylation, translocation of enzyme activity to the membrane fraction, potentiatory and inhibitory effect on platelet activation ([Ca2+]i, arachidonate and granule release) showed an absolute dependence on [Na+]e. With the exception of dense-granule release, which was clearly potentiated by the removal of [Na+]e and showed a negative correlation with exchanger activity, the other effects of PMA and diC8 were not affected by [Na+]e removal. It is concluded that Na+/H+ exchange is not essential for protein kinase C activation in platelets.

Extracellular Na+ removal enhances granule secretion in platelets--evidence that Na+/H+ exchange is inhibitory to secretion induced by some agonists

The effect of extracellular Na+ [( Na+]e) removal on agonist-induced granule secretion in platelets in relation to [pH]i and [Ca2+]i changes was investigated. Substitution of [Na+]e with choline+ of K+ resulted in a significant enhancement of 5HT secretion induced by thrombin, collagen, U46619 and the protein kinase C activators, PMA and diC8. Increases in [Ca2+]i induced by thrombin and U46619 were slightly inhibited or unaffected in these buffers, but [pH]i increases induced by thrombin, U46619, PMA and diC8 were abolished and a drop in [pH]i (0.05 0.1 units below resting) was observed. Although preincubation with potassium acetate produced a big drop in [pH]i and greatly increased secretion with all the agonists, particularly in the absence of [Na+]e, clear evidence that [pH]i rises due to Na+/H+ exchange are inhibitory to secretion was obtained only with thrombin. Thus, (i) NH4Cl, which restored the increase in [pH]i in the absence of [Na+]e reduced the potentiated secretory response to thrombin, (ii) no increase in thrombin-induced secretion was observed when Na+ was replaced with Li+, which allowed a normal increase in [pH]i and (iii) ethyl isopropyl amiloride (EIPA) abolished the [pH]i rise and potentiated thrombin-induced secretion. With collagen and U46619, the results suggest that removal of [Na+]e per se rather than inhibition of Na+/H+ exchange results in enhanced secretion. It is concluded that [Na+]e per se and [pH]i elevations via Na+/H+ exchange both have important inhibitory roles in the control of platelet granule secretion.