Low dose gemcitabine plus cisplatin in a weekly-based regimen as salvage therapy for relapsed breast cancer after taxane-anthracycline-containing regimens.

PURPOSE: Cisplatin-gemcitabine is a synergistic chemotherapy (CT) combination highly proven in a broad spectrum of epithelial neoplasms and shows a non-cross-resistance profile with the most active drugs in metastatic breast cancer (MBC). We have conducted an exploratory study to determine if treatment with low doses of a combination of fixed-rate gemcitabine infusion and cisplatin was clinically meaningful in women relapsing after a minimum of 2 prior lines of CT for advanced disease (range 2-6), which had to have necessarily included both anthracyclines and taxanes. Another goal was to find the optimal individual schedule by adjusting frequency and dosage according to patient tolerability. PATIENTS AND METHODS: From May 2002 to November 2003, 22 patients with relapsed advanced BC and a minimum of two prior CT lines were offered treatment with gemcitabine (G) (initial dose 750 mg/m(2), or 600 mg/m(2) if the patient had received more than two previous CT lines) plus cisplatin (P) (initial dose 30 mg/m(2), or 20 mg/m(2) in case of > or =3 prior CT lines) on days 1 and 8 of a 21-day cycle. Treatment was postponed to day 15 if it could not be given on day 8, without dose reduction. If treatment could not be given on day 15, a 20% dose reduction was allowed and treatment given the next week. Further dose reductions were allowed as needed up to a maximum of three. Treatment continued until disease progression or intolerable toxicity. Median age was 54.5 years (35-75). Median Karnofsky was 90 (range 80-90). Median number of prior CT lines was 3 (2-6). 90.9% of patients had received adjuvant CT. All had prior anthracyclines and taxanes. Other agents used included 5-FU/eniluracil, MTA, RPR 109881A, trastuzumab, cisplatin, VP16, vinorelbine, capecitabine and irinotecan. 72.7% had received radiotherapy and 68.1% hormonal therapy (median 2 lines, range 1-4). RESULTS: Partial responses (PR) were seen in 9.1% of patients and stable disease (SD) in 36.4%. Clinical Benefit Rate (PR+SD) was derived in 45.5% of patients. Median time to progression was 4 months (95% CI, 3-5) in general and 6 months (95% CI, 4-8) in patients with clinical benefit. Median survival for the entire group was 8 months (95% CI, 5-11) and 19 months when clinical benefit was obtained (95% CI, 11-25). Patients received a median of 8.5 CT administrations (range, 2-45). Forty-three percent of doses were delayed. Sixteen out of 22 patients needed a delay and/or reduction of initial dose. Cisplatin and gemcitabine doses were reduced in 75% and 62% of all cycles, respectively. Sixteen out of 22 patients needed a delay and/or reduction of initial dose. Toxicities grade >3 were neutropenia 35% and thrombocytopenia 15%. All other toxicities were grade 2 or less, including sensorial neuropathy (30%), asthenia (34%), nausea/vomiting (20%) and oral mucositis (15%). There were no treatment-related deaths. Reasons for discontinuation were progression (18 patients), death (3 patients) and patient decision (1 patient). CONCLUSION: Weekly cisplatin-gemcitabine with flexible downwards individual tailoring is a safe and effective salvage treatment in heavily pretreated MBC patients with good PS.

Low dose gemcitabine plus cisplatin in a weekly-based regimen as salvage therapy for relapsed breast cancer after taxane-anthracycline-containing regimens

PURPOSE: Cisplatin-gemcitabine is a synergistic chemotherapy (CT) combination highly proven in a broad spectrum of epithelial neoplasms and shows a non-cross-resistance profile with the most active drugs in metastatic breast cancer (MBC). We have conducted an exploratory study to determine if treatment with low doses of a combination of fixed-rate gemcitabine infusion and cisplatin was clinically meaningful in women relapsing after a minimum of 2 prior lines of CT for advanced disease (range 2-6), which had to have necessarily included both anthracyclines and taxanes. Another goal was to find the optimal individual schedule by adjusting frequency and dosage according to patient tolerability. PATIENTS AND METHODS: From May 2002 to November 2003, 22 patients with relapsed advanced BC and a minimum of two prior CT lines were offered treatment with gemcitabine (G) (initial dose 750 mg/m(2), or 600 mg/m(2) if the patient had received more than two previous CT lines) plus cisplatin (P) (initial dose 30 mg/m(2), or 20 mg/m(2) in case of > or =3 prior CT lines) on days 1 and 8 of a 21-day cycle. Treatment was postponed to day 15 if it could not be given on day 8, without dose reduction. If treatment could not be given on day 15, a 20% dose reduction was allowed and treatment given the next week. Further dose reductions were allowed as needed up to a maximum of three. Treatment continued until disease progression or intolerable toxicity. Median age was 54.5 years (35-75). Median Karnofsky was 90 (range 80-90). Median number of prior CT lines was 3 (2-6). 90.9% of patients had received adjuvant CT. All had prior anthracyclines and taxanes. Other agents used included 5-FU/eniluracil, MTA, RPR 109881A, trastuzumab, cisplatin, VP16, vinorelbine, capecitabine and irinotecan. 72.7% had received radiotherapy and 68.1% hormonal therapy (median 2 lines, range 1-4). RESULTS: Partial responses (PR) were seen in 9.1% of patients and stable disease (SD) in 36.4%. Clinical Benefit Rate (PR+SD) was derived in 45.5% of patients. Median time to progression was 4 months (95% CI, 3-5) in general and 6 months (95% CI, 4-8) in patients with clinical benefit. Median survival for the entire group was 8 months (95% CI, 5-11) and 19 months when clinical benefit was obtained (95% CI, 11-25). Patients received a median of 8.5 CT administrations (range, 2-45). Forty-three percent of doses were delayed. Sixteen out of 22 patients needed a delay and/or reduction of initial dose. Cisplatin and gemcitabine doses were reduced in 75% and 62% of all cycles, respectively. Sixteen out of 22 patients needed a delay and/or reduction of initial dose. Toxicities grade >3 were neutropenia 35% and thrombocytopenia 15%. All other toxicities were grade 2 or less, including sensorial neuropathy (30%), asthenia (34%), nausea/vomiting (20%) and oral mucositis (15%). There were no treatment-related deaths. Reasons for discontinuation were progression (18 patients), death (3 patients) and patient decision (1 patient). CONCLUSION: Weekly cisplatin-gemcitabine with flexible downwards individual tailoring is a safe and effective salvage treatment in heavily pretreated MBC patients with good PS (AU)

Effect of sulfur availability on the integrity of amino acid biosynthesis in plants.

Amino acid levels in plants are regulated by a complex interplay of regulatory circuits at the level of enzyme activities and gene expression. Despite the diversity of precursors involved in amino acid biosynthesis as providing the carbon backbones, the amino groups and, for the amino acids methionine and cysteine, the sulfhydryl group and despite the involvement of amino acids as substrates in various downstream metabolic processes, the plant usually manages to provide relatively constant levels of all amino acids. Here we collate data on how amino acid homeostasis is shifted upon depletion of one of the major biosynthetic constituents, i.e., sulfur. Arabidopsis thaliana seedlings exposed to sulfate starvation respond with a set of adaptation processes to achieve a new balance of amino acid metabolism. First, metabolites containing reduced sulfur (cysteine, glutathione, S-adenosylmethionine) are reduced leading to a number of downstream effects. Second, the relative excess accumulation of N over S triggers processes to dump nitrogen in asparagine, glutamine and further N-rich compounds like ureides. Third, the depletion of glutathione affects the redox and stress response system of the glutathione-ascorbate cycle. Thus, biosynthesis of aromatic compounds is triggered to compensate for this loss, leading to an increased flux and accumulation of aromatic amino acids, especially tryptophan. Despite sulfate starvation, the homeostasis is kept, though shifted to a new state. This adaptation process keeps the plant viable even under an adverse nutritional status.

Fructan synthesis is inhibited by phosphate in warm-grown, but not in cold-treated, excised barley leaves.

The inhibition of fructan accumulation by phosphate was investigated in warm-grown and cold-treated barley (Hordeum vulgare) plants. Detached leaves were incubated in water or phosphate for 24 h under lighting or in darkness. Fructosyltransferase, sucrose phosphate synthase (SPS) and cytosolic fructose-1,6-bisphosphatase (FBPase) activities were subsequently analysed, as well as the content of carbohydrates, hexose-phosphates, phosphate, amino acids and protein. In warm-grown leaves, phosphate decreased fructan accumulation and total carbon in carbohydrates and did not affect protein content. Phosphate increased hexose-phosphates, phosphate and amino acids. Fructosyltransferase and FBPase activities were not affected by phosphate feeding, while SPS activity was inhibited by phosphate in incubations in both light and darkness. In cold-treated leaves, which before incubation had higher SPS activities than warm-grown leaves, phosphate had no inhibitory effect on fructan accumulation, carbohydrate content or total C in carbohydrates. The activities of SPS and FBPase were unaffected by phosphate. The results indicate that phosphate decreases fructan accumulation through an inhibition of SPS whenever this activity is not high before a rise in phosphate content.

Nitrate is a negative signal for fructan synthesis, and the fructosyltransferase-inducing trehalose inhibits nitrogen and carbon assimilation in excised barley leaves.

• Fructan biosynthesis in barley (Hordeum vulgare) has been shown to be upregulated by sugar signalling and downregulated by nitrogen. The relationship between these two regulations is investigated. • Excised third-leaves of barley were fed nitrate or glutamine under two light intensities. Other leaf blades were supplied in the dark for 24 h with nitrate and trehalose in the presence of validamycin A, a trehalase inhibitor. • In the light, nitrate, but not glutamine, decreased fructan contents and sucrose:fructan 6-fructosyltransferase protein without affecting the levels of sucrose and other carbohydrates. In darkened leaves, trehalose increased and nitrate decreased the fructan contents and total sucrose:fructosyltransferase activity without altering the concentration of sucrose. The effect on fructan contents of trehalose disappeared, whereas that of nitrate remained in subsequent incubations in water under light. Trehalose decreased and nitrate increased the light- and CO2 -saturated rate of photosynthesis without significantly affecting the initial Rubisco (ribulose-1,5-bisphosphate carboxylase oxygenase) activity. Trehalose feeding decreased the activation of nitrate reductase and amino acid levels, and blocked the positive effect of nitrate on the maximal activity of this enzyme. • The results indicate that nitrate, and not a downstream metabolite, is a negative signal for fructan synthesis, independent from the positive sugar signalling and overriding it. Trehalose signalling inhibits nitrogen and carbon assimilation, at the same time, inducing fructosyltransferase activity.

Tobacco mutants with a decreased number of functional nia genes compensate by modifying the diurnal regulation of transcription, post-translational modification and turnover of nitrate reductase.

Although nitrate reductase (NR. EC 1.6.6.1) is thought to control the rate of nitrate assimilation, mutants with 40-45% of wildtype (WT) NR activity (NRA) grow as fast as the WT. We have investigated how tobacco (Nicotiana tabacum L. cv. Gatersleben) mutants with one or two instead of four functional nia genes compensate. (i) The nia transcript was higher in the leaves of the mutants. However, the diurnal rhythm was retained in the mutants, with a maximum at the end of the night and a strong decline during the photoperiod. (ii) Nitrate reductase protein and NRA rose to a maximum after 3-4 h light in WT leaves, and then decreased by 50-60% during the second part of the photoperiod and the first part of the night. Leaves of mutants contained 40-60% less NR protein and NRA after 3-4 h illumination, but NR did not decrease during the photoperiod. At the end of the photoperiod the WT and the mutants contained similar levels of NR protein and NRA. (iii) Darkening led to a rapid inactivation of NR in the WT and the mutants. However, in the mutants, this inactivation was reversed after 1-3 h darkness. Calyculin A prevented this reversal. When magnesium was included in the assay to distinguish between the active and inactive forms of NR, mutants contained 50% more activity than the WT during the night. Conversion of [15N]-nitrate to organic compounds in leaves in the first 6 h of the night was 60% faster in the mutants than in the WT. (iv) Growth of WT plants in enhanced carbon dioxide prevented the decline of NRA during the second part of the photoperiod, and led to reactivation of NR in the dark. (v) Increased stability of NR in the light and reversal of dark-inactivation correlated with decreased levels of glutamine in the leaves. When glutamine was supplied to detached leaves it accelerated the breakdown of NR, and led to inactivation of NR, even in the light. (vi) Diurnal changes were also investigated in roots. In the WT, the amount of nia transcript rose to a maximum after 4 h illumination and then gradually decreased. The amplitude of the changes in transcript amount was smaller in roots than in leaves, and there were no diurnal changes in NRA. In mutants, nia transcript levels were high through the photoperiod and the first part of the night. The NRA was 50% lower during the day but rose during the night to an activity almost as high as in the WT. The rate of [15N]-nitrate assimilation in the roots of the mutants resembled that in the WT during the first 6 h of the night. (vii) Diurnal changes were also compared in Nia30(145) transformants with very low NRA, and in nitrate-deficient WT plants. Both sets of plants had similar low growth rates. Nitrate reductase did not show a diurnal rhythm in leaves or roots of Nia30(145), the leaves contained very low glutamine, and NR did not inactivate in the dark. Nitrate-deficient WT plants were watered each day with 0.2 mM nitrate. After watering, there was a small peak of nia transcript NR protein and NRA and, slightly later, a transient increase of glutamine and other amino acids in the leaves. During the night glutamine was low, and NR did not inactivate. In the roots, there was a very marked increase of nitrate, nia transcript and NRA 2-3 h after the daily watering with 0.2 mM nitrate. (viii) It is concluded that WT plants have excess capacity for nitrate assimilation. They only utilise this potential capacity for a short time each day, and then down-regulate nitrate assimilation in response, depending on the conditions, to accumulation of the products of nitrate assimilation or exhaustion of external nitrate. Genotypes with a lower capacity for nitrate assimilation compensate by increasing expression of NR and weakening the feedback regulation, to allow assimilation to continue for a longer period each day.