Survival following early-stage colon cancer: an ACCENT-based comparison of patients versus a matched international general population†

BACKGROUND

Post-treatment survival experience of early colon cancer (CC) patients is well described in the literature, which states that cure is probable for some patients. However, comparisons of treated patients' survival versus that expected from a matched general population (MGP) are limited.

PATIENTS AND METHODS

A total of 32 745 patients from 25 randomized adjuvant trials conducted from 1977 to 2012 in 41 countries were pooled. Observed long-term survival of these patients was compared with expected survival matched on sex, age, country, and year, both overall and by stage (II and III), sex, treatment [surgery, 5-fluorouracil (5-FU), 5-FU + oxaliplatin], age (<70 and 70+), enrollment year (pre/post 2000), and recurrence (yes/no). Comparisons were made at randomization and repeated conditional on survival to 1, 2, 3, and 5 years. CC and MGP equivalence was tested, and observed Kaplan-Meier survival rates compared with expected MGP rates 3 years out from each landmark. Analyses were also repeated in patients without recurrence.

RESULTS

Within most cohorts, long-term survival of CC patients remained statistically worse than the MGP, though conditional survival generally improved over time. Among those surviving 5 years, stage II, oxaliplatin-treated, elderly, and recurrence-free patients achieved subsequent 3-year survival rates within 5% of the MGP, with recurrence-free patients achieving equivalence.

CONCLUSIONS

Conditional on survival to 5 years, long-term survival of most CC patients on clinical trials remains modestly poorer than an MGP, but achieves MGP levels in some subgroups. These findings emphasize the need for access to quality care and improved treatment and follow-up strategies.

Treatment of adult osteosarcoma - single-center results in 47 patients

Fourty-seven adult patients (median age 24 years; 16-66 years) with the diagnosis of osteosarcoma were treated at Hannover University Medical School between 1980 and 1991 according to the consecutive protocols of the Osteosarcoma Study Group (COSS-80 - COSS-86) irrespective of the fulfilment of study entry criteria. Patients received preoperative chemotherapy followed by surgical resection and adjuvant postoperative chemotherapy. Thirty-seven patients (79%) were treated for local tumors and 10 patients (21%) presented with disseminated metastatic disease. Twenty-one patients (45%) did not fulfil official study entry criteria. Thirty-four patients (72%) achieved an NED-status after therapy, 13 patients (28%) still had metastases and/or unresectable tumors. Seventeen of 34 patients (50%) relapsed after a median time of 18.5 months. Only 1 of 10 patients presenting initially with metastatic disease could be rendered long term tumor-free. The median overall survival of all patients was 42 months with a 2-year-survival rate of 64%. The projected 5-year-survival after a median follow-up of 59 months (8-121 months) was 49%. The presence of metastatic disease at initial diagnosis (p=0.04), an elevated alkaline phosphatase level at diagnosis (p=0.05), histologically 'poor response' to preoperative chemotherapy (p=0.04) and non-fulfilment of COSS-study entry criteria (p=0.046) were significantly worse prognostic factors during univariate analysis. The treatment results in unselected adult patients with osteosarcoma are inferior to those reported for patients included into osteosarcoma treatment study protocols. However, appoximately half of all patients (45%) seen at a large single center did not fulfil the eligibility criteria as official study patients. Even in these non-study patients the use of preoperative and/or adjuvant chemotherapy significantly improved survival compared to historical controls treated by surgery alone (58% and 38% 2- and 5-year-survival rates, respectively). The prognosis of patients with synchronous metastases at diagnosis remains poor despite the inclusion of chemotherapy into treatment strategies.

Hepatic arterial infusion of the nitrosourea derivate fotemustine for the treatment of liver metastases from colorectal carcinoma

The chloroethylnitrosourea derivate diethyl-1-(3-(2-chloroethyl)-3-nitroso-ureido)-ethyl phosphonate fotemustine (FM) was investigated in a open monocentric clinical-pharmacological trial. Seventeen patients, with a median age of 57 years and progressive hepatic metastases from colorectal carcinoma received regional treatment with a stepwise dose-escalated regimen of FM to define the maximally tolerated dose. Thrombo- and leukocytopenia were dose-limiting with median nadir at day 29 (range, 19-79) and day 39 (range, 19-78), respectively. Local side-effects in the liver were mild with only transiently elevated enzymes. No other severe side-effects, except pain (WHO grade III) in one patient after the infusion of FM was noted. The maximally tolerated dose was 125 mg/m(2)/day. Plasma profiles followed a mono-exponential law (one-compartment-model). Systemic concentrations measured as area under the time-concentration curve (AUG) indicated a short plasma half-life (t(1/2)=25.8+/-11.5 min) and a high body clearance (C-L=2.193+/-870 ml/min) with large inter- and intra-individual variations. Of fifteen evaluable patients examined with CT-scan, one complete, three partial, one minor response and seven patients with stable disease were observed [ORR=27%, IC95% (4.5-49.5%)]. In summary, hepatic arterial infusion of FM appears to be effective treatment for liver metastases from colorectal carcinoma. Considering the absence of mucositis/diarrhea and hepatic toxicity, FM could be explored as an alternative to 5-FUDR or 5-FU in previously untreated patients with isolated liver metastases.

Preliminary results of an ongoing phase II/III clinical study of the TLR9 agonist MGN1703 in patients with advanced colorectal carcinoma with disease control after first-line induction therapy (IMPACT Study)

618

Background: MGN1703 is a synthetic DNA-based immunomodulator, which acts as an agonist of toll-like receptor 9. The antineoplastic activity of MGN1703 was previously shown in several in-vitro and in-vivo models. A good safety profile of MGN1703 was shown in regulatory required acute and chronic toxicity studies. A currently finished phase I study in patients with metastatic solid tumors including those with CRC provided evidence for a favorable safety profile of the investigational drug as well as demonstrated positive preliminary efficacy results. Based on these promising data, a phase II/III study was initiated in patients with advanced CRC.

Methods: This international multicentric randomized placebo-controlled phase II/III clinical study is being conducted in patients with advanced CRC with disease control after first-line induction therapy with standard chemotherapy regimen in combination with bevacizumab. One hundred and twenty nine patients have to be recruited to the study and randomized to be treated ether with MGN1703 or with placebo (with a ratio of 2:1), respectively. The recruited patients are treated twice a week with subcutaneous administration of 60 mg MGN1703. This dose has been proven to be safe in the phase I clinical study. The efficacy and safety of the study treatment will be evaluated based on extensive immunological tests, radiological assessment, safety laboratory results and assessments of the quality of life. The study treatment will be continued up to occurrence of tumor progression, intolerable toxicity, exclusion criteria, and withdrawal of consent or death.

[Table: see text]

Comparative clinical efficacy of adjuvant chemotherapy regimens in randomized controlled trials (RCTs) of early-stage colon cancer: Systematic review and meta-analysis

498

Background: A systematic review was conducted to identify RCTs of adjuvant chemotherapy regimens for early-stage colon cancer and a network meta-analysis performed to compare efficacy of oxaliplatin/fluoropyrimidine regimens.

Methods: A systematic review identified RCTs recruiting adult patients with early-stage (adjuvant) stage II/III colon cancer. Outcome measures included hazard ratios for DFS and OS. Only publications in English were considered. Study quality was assessed using the Cochrane Collaboration “risk of bias” assessment tool. A single reviewer screened abstracts/titles using predefined selection criteria, with critical appraisal and data extraction conducted independently by two reviewers. A Bayesian network meta-analysis was used to estimate comparative efficacy of adjuvant chemotherapy across RCTs.

Results: 56 articles describing 40 trials were selected, of which six reported data on regimens accepted as current standard of care (capecitabine/X-ACT, XELOX/NO16968, FOLFOX/MOSAIC, FLOX/C-07) or common comparators: bolus 5FU/LV and LV5FU2 (C-96-1, PETACC-2). Statistical assessment of heterogeneity was not possible due to the limited study network. Baseline characteristics were similar across trials with the exception of three trials recruiting only stage III patients; sub-group analysis on these trials was not possible due to lack of common comparators. There was no significant difference in DFS at a median follow-up of 3-years (or closest reported analysis) for XELOX vs. FLOX (HR=0.99, 95% CI 0.80–1.22) or FOLFOX (HR=1.00, 95% CI 0.72–1.41). There was also no significant difference in OS at a median follow-up of at least 5 years. Taken as a class, oxaliplatin-containing regimens (XELOX, FOLFOX, FLOX) improved DFS vs. non-oxaliplatin-containing regimens (HR=0.80, 95% CI 0.73–0.87). This result was confirmed for OS.

Conclusions: Despite the limited number of available trials, the results of these analyses demonstrate a clear benefit of incorporating oxaliplatin into combination regimens for early-stage colon cancer. XELOX, FOLFOX and FLOX appear to be equivalent in terms of efficacy in this setting.

[Table: see text]

Effective management of patients receiving XELOX: Evaluation of impact of dose modifications on outcome in patients from the NO16966, NO16967, and NO16968 trials

497

Background: In patients (pts) with metastatic colorectal cancer (MCRC), XELOX is non-inferior to FOLFOX4 in terms of PFS and OS as either first-line (NO16966, Cassidy et al. JCO 2008) or second-line therapy (NO16967, Rothenberg et al. Ann Oncol 2008). In pts with stage III colon cancer (NO16968, Haller et al. ECCO-ESMO 2009), adjuvant XELOX is superior to 5-FU/LV in terms of DFS. While XELOX is generally well tolerated, regional differences in fluoropyrimidine tolerability were noted in a pooled analysis [Rothenberg et al. ASCO GI 2008], leading to use of lower than recommended doses of capecitabine (i.e. 1,000mg/m2 bid d1–15 with oxaliplatin 130mg/m2 d1 q3w) in some countries.

Methods: NO16966, NO16967 and NO16968 protocols included standard dose/schedule modifications for capecitabine, 5-FU and oxaliplatin for treatment-related adverse events (AEs). Safety parameters included AEs, deaths, laboratory parameters, exposure to trial medication, and withdrawals. In NO16966 and NO16967, Kaplan-Meier curves for PFS were developed for pts with no treatment modifications, and pts with dose reductions, treatment interruptions or cycle delays to assess the effect of treatment modifications on efficacy. NO16968 also included a planned analysis of the effect of dose modifications on DFS.

Results: NO16966 included 1335 pts with previously untreated MCRC receiving XELOX or FOLFOX4. NO16967 included 627 pts with previously treated MCRC receiving XELOX or FOLFOX4. NO16968 included 1886 pts with resected stage III disease receiving XELOX or 5-FU/LV; dose modifications were required for capecitabine in 65% and oxaliplatin in 62% of pts in NO16968. Kaplan-Meier curves of PFS (NO16966/NO16967) or DFS (NO16968) for pts who did and did not require dose modifications indicated that the efficacy of XELOX did not appear to be compromised by dose modifications. Indeed, pts who required dose modifications seemed to have a favourable outcome compared with those who did not.

Conclusions: From these data we cannot make a recommendation that initial dosing should be lower than the labeled dose. However, it is clear that dose modification does not seem to impact patient outcome.

[Table: see text]

Docetaxel, oxaliplatin, and capecitabine (TEX regimen) for patients with metastatic gastric cancer: Interim results from a phase II trial by the German AIO Group

4554

Background: Combination regimens of 3 drugs have shown promising activity as treatment for patients (pts) with metastatic gastric cancer (GC). Docetaxel combined with cisplatin and 5-FU (CF) improved overall survival and response rates when compared to standard CF. However, the identification of less toxic and more convenient variants of this regimen is still important. We have previously established a regimen with docetaxel (T) combined with oxaliplatin (E) and capecitabine (X) in a phase I trial [Grothe et al., Proc. ASCO 2006]. Results of a preplanned interim analysis of subsequent multicenter phase II trials of the TEX regimen are presented here. Methods: Pts with metastatic or locally advanced GC, adequate organ function, ECOG PS 0–2, and no prior chemotherapy for advanced disease (adjuvant allowed) were enrolled. TEX regimen was administered as defined: T 35 mg/m2 and E 70 mg/m2 on days (d) 1 and 8, with X 800 mg/m2 bid on d1–14 every 22 days Toxicity assessment was done 3-weekly while CT scans were repeated 9-weekly. Results: 35 of 48 pts were enrolled until 06/08: 28 male / 7 female, median age 59 (36–81) years, ECOG PS 0/1/2 69%/31%/0%, gastric / gastroesophageal cancer 60%/40%, distant metastases 96%, tumor in situ 37%. The most common toxicities reported were (CTC grade [gr] 3/4): diarrhea 20%/3%, vomiting 11%/3%, asthenia and neurotoxicity each 9%/0%. Mucositis and hand-foot-syndrome were observed in (grade 1+2 / grade 3) 29%/0% and 26%/3%, respectively. Hematoxicity was mild with grade 3 anemia in 10% and no other grade 3/4 toxicity except one episode of febrile neutropenia . Of 25 pts evaluable so far, first tumor response assessment revealed (RECIST criteria) partial response in 36% and stable disease in 40% of patients. Conclusions: TEX is a safe and tolerable regimen for patients with metastatic gastric cancer. Preliminary efficacy results indicate promising activity. Mature data including progression free survival will be presented at the meeting.

[Table: see text]

Activity of mTOR-Inhibitor Rad001 (everolimus) in differentiated and anaplastic thyroid cancer cell lines

e14608

Background: Recent data suggest that aberrant activation of PIK3/AKT-pathway and mTOR are involved in the development of thyroid cancer, particularly of anaplastic (ATC) and follicular (FTC) subtype. Therefore, mTOR could be a potential treatment target in thyroid cancer. Methods: To asses the potential role of mTOR as target for the treatment of thyroid cancer, two human ATC cell lines SW1736 and 8505C, the papillary thyroid cancer (PTC) cell line BCPAP and the FTC cell line FTC133 were exposed for 96h to increasing concentrations of the mTOR inhibitor RAD001 (Everolimus, kindly provided by Novartis, Switzerland). For combination experiments 10 nM of RAD001 were combined with increasing concentrations of either doxorubicin (DOX) or cisplatin (CDDP) continuously. Cytotoxicity was measured using the sulforhodamine B assay. IC50-values were calculated with Sigma Plot (Jandel Scientific) and drug interaction was determined by the model of Drewinko. Results: The observed IC50-values of RAD001 were 1nM (FTC133), 10 nM (BCPAP), 1000 nM (SW1736) and 9400 nM (8505C). In contrast to the pronounced differences in sensitivity as assessed on the basis of IC50, a growth inhibitory effect ≥ 25 % was seen in all cell lines at a concentration of 1 nM of RAD001. IC50 for CDDP ranged from 1,3–4,8 μM and for DOX from 8–40 nM. Combination of 10 nM RAD001 with either DOX or CDDP resulted in additive drug interaction with the exception in cell line 8505C where significant synergy was found for the combination with CDDP. Conclusion: RAD001 exerted interesting preclinical activity in two differentiated thyroid cancer cell lines. Mainly additive drug interaction in thyroid cancer cell lines was observed for combinations with CDDP and DOX. Mechanistic investigations are underway and will be presented at the meeting. At least for differentiated thyroid cancer mTOR-inhibition appeared promising, further evaluation in thyroid cancer seems warranted.

No significant financial relationships to disclose.

Aprepitant for the prevention of chemotherapy-induced nausea and vomiting associated with a broad range of moderately emetogenic chemotherapies and tumor types: A randomized, double-blind study

9626

Background: Aprepitant (A) has been shown in a previous trial to be effective for prevention of chemotherapy-induced nausea and vomiting (CINV) with moderately emetogenic chemotherapy (MEC) in breast cancer patients receiving cyclophosphamide and anthracycline. This study assessed A in patients with a variety of tumors receiving a broad range of MEC regimens. Methods: This Phase III, randomized, gender-stratified, double-blind, trial enrolled female and male patients ≥18 years old with confirmed malignancies naïve to MEC or highly emetogenic chemotherapy and scheduled to receive a single dose of 1 or more MEC agent. Patients received A triple-therapy regimen (A 125 mg, ondansetron [O] 8 mg b.i.d., and dexamethasone [D] 12 mg on Day 1 of chemotherapy, A 80 mg q.d. on Days 2–3) or a control regimen (O 8 mg b.i.d. and D 20 mg on Day 1, and O 8 mg q12h on Days 2–3) all administered orally. Episodes of vomiting, nausea, and rescue medication use were recorded in a patient diary. Tolerability was assessed by physical and lab examinations, and adverse event (AE) reporting. Primary and key secondary efficacy endpoints were proportions of patients with No Vomiting and Complete Response (no vomiting and no rescue medication use), respectively, during the 120 hours postchemotherapy. Results: Among 848 randomized patients, 77% were female while 52, 20, 13, and 5% of patients had breast, colorectal, lung, or ovarian cancer, respectively. Significantly more patients in the A group achieved No Vomiting and Complete Response (a difference of 14.1 &12.4 percentage points vs. control, respectively). The incidences of AEs were generally similar in the aprepitant (61.9%) and control groups (66.5%). Conclusions: The aprepitant regimen provided superior efficacy over the control regimen in the treatment of CINV in a broad range of patients receiving MEC in both No Vomiting and Complete Response endpoints. Aprepitant was generally well tolerated. [Table: see text]

[Table: see text]

Comparable safety and response rate with bevacizumab in combination with capecitabine/oxaliplatin (CapOx/Bev) versus capecitabine/irinotecan (CapIri/Bev) in advanced CRC (mCRC): A randomized phase II study of the AIO GI tumor study group

4034

Background: Bevacizumab (Bev) combined with 5-FU/FA and both, irinotecan or oxaliplatin are standard regimens for mCRC. Recently, a phase III trial has demonstrated that infusional 5-FU can be substituted by capecitabine (cape) when combined with oxaliplatin and Bev whereas conflicting data are available for feasibility and efficacy of cape/irinotecan combinations. This randomized phase II trial was to compare safety and efficacy of Bev with either CapOx or CapIri in untreated mCRC. Methods: Eligibility criteria: untreated mCRC pts, ECOG PS <= 2, measurable lesion(s), adequate hematologic and organ function. Primary endpoint was % of pts progression-free after 6 months. Treatment plan: Bev 7.5 mg/kg day (d)1 with either oxaliplatin (130 mg/m2 d1)/cape (1,000 mg/m2 bid d1–14; CapOx/Bev, arm A) or irinotecan (200 mg/m2 d1)/cape (800 mg/m2 bid d 1–14; CapIri/Bev, arm B), all q d22. Arm B doses were 20% lower for both, cape and irinotecan, compared to previous trials reporting an unacceptable toxicity profile (Köhne, ASCO 2005). Treatment was continued until progression or unacceptable toxicity. Results: So far, toxicity data are available on 228 (118/110 pts arm A/B) of total 240 pts. Baseline characteristics (arm A/B): median age 64/65 yrs, male 67%/68%. A total of 684/719 cycles (median 6/6 cycles) have been administered. Most common CTC grade 3/4 toxicities (% of pts): Diarrhea 17.0/15.5, hand-foot-syndrome 5.9/2.7, peripheral neuropathy 15.3/0.0. Specific AE′s such as thrombosis, 3° hypertension and GI perforation occurred in 3.4/4.5%, 3.4/0.9% and 0.9/0.9% of pts, respectively. Among 185 evaluable pts (96/89), tumor control rates (CR+PR+SD) in arm A/B were 81.4%/82.8%, overall response rates (CR+PR) were 49.0%/52.7%. Conclusions: Both regimens, CapOx/Bev and CapIri/Bev, are well tolerated without differences in toxicity (except neuropathy). Interestingly, despite the protocol defined dose reduction of CapIri there is seemingly no difference in efficacy as measured by tumor control and response rate. Meanwhile, the trial has finished accrual and data including PFS rate will be presented at the meeting.

[Table: see text]

BECAM: A salvage protocol with bevacizumab, capecitabin, and mitomycin C for patients with refractory metastatic colorectal cancer (CRC) or gastric cancer (GC)

13554

Background: Bevacizumab (Bev), a monoclonal antibody targeted against VEGF, has shown to improve efficacy in CRC when combined with chemotherapy. Combination schedules of fluoropyrimidines with mitomycin C (MMC) are active in both CRC and GC. This study was to explore the combination of Bev with a previously reported schedule of Capecitabine (Cap) and MMC (BECAM) in heavily pretreated patients (pts) with GC or CRC. Methods: Pts had to be refractory to at least 3 treatment lines, incl. 5-FU, oxaliplatin, irinotecan, and cetuximab in CRC; 2 lines with 5-FU, platinum, irinotecan or taxane in GC. A treatment cycle consisted of a 1-hour-infusion of Bev 7.5 mg/kg d1, bolus MMC 7mg/m2 d1 and Cap 1000mg/m2 bid d1–14, all qd22. Toxicity was assessed every 3 weeks (wk) and tumor evaluation (CT/MRI) was done every 9 wk. Results: 19 pts were included: m/f 8/11; GC 4, CRC 15, age 63 yrs [42–76], Karnofsky PS 80% [70–100]. Median no. of preceding regimens was 3 [2–6]. A total of 87 cycles were given. Median no. of cycles per pt. was 3 [2–15]. 18 pts were evaluable for toxicity (WHO scale) and efficacy: Grade 3/4 toxicities were thrombocytopenia (5/0), hypertension (1/0), and hemorrhage (0/1). The latter caused cessation of further administration of Bev. Gastrointestinal and other hematologic toxicities did not exceed grade 2. Response: PR was seen in 3 pts (16%; 1/4 GC, 2/14 CRC), stable disease for > 9 wk in 5 pts (1 GC, 4 CRC), leading to a tumor control rate of 44%. Median progression free and overall survival were 3.0 [2–11] and 5.0 [2.5–13] months. However, duration of objective response was remarkable in lasting 7.4–10.0 months. Conclusions: BECAM shows considerable activity in this group of heavily pretreated pts with CRC or GC. Toxicity was generally mild except for MMC-induced thrombocytopenia and (probably) Bev-induced bleeding (gastric tumor site). Despite previous reports of limited activity with Bev/5-FU in refractory pts (NCI TRC trial), BECAM is able to induce long lasting objective responses and therefore merits further investigation in both tumor types.

[Table: see text]

Phase I trial of docetaxel, oxaliplatin and capecitabine (TEX) in patients with metastatic gastric cancer

14051

Background: Combination regimens of 3 active drugs have shown promising activity in treatment of metastatic gastric cancer (GC). Docetaxel (D) combined with cisplatin and 5-FU (CF) yielded superior overall survival and response rates when compared to standard CF. However, toxicity profile showed the need for development of less toxic modifications. In this phase I trial, D was combined with oxaliplatin (Ox) and capecitabine (Cape) in order to define the maximum tolerated dose (MTD) and dose-limiting toxicities (DLT) in patients (pts) with metastatic GC. Methods: Pts had to have metastatic or locally advanced GC, adequate organ function, ECOG PS 0–2, no prior chemotherapy. Four dose levels were planned planned for the TEX regimen: D 35–40 mg/m2, Ox 70 mg/m2 d1 and d88, with Cape 800–1000 mg/m2 bid d1–14 q d22. Toxicity was assessed 3-weekly whereas CT scans were repeated 9-weekly. Results: 14 pts were enrolled: 9m/5f, age 64 (42–76) yrs, ECOG PS 1 [0–2]. All pts. had distant metastatis, 10 no gastrectomy. On dose level 1 (D 35 mg/m2, Ox 70 mg/m2, Cape 800 mg/m2) 3 pts were included initially. 1 pt. had grade 4 bleeding from primary tumor site after 2nd administration and therefore was excluded. For safety reasons, 6 more pts. were enrolled - without further DLT. On dose level 2 (D 40 mg/m2, Ox 70 mg/m2, Cape 800 mg/m2), diarrhea and mucositis grade 3 occurred as DLT in 2/2 patients. Level 1 was determined as MTD and 5 more pts were included to a total of 12 with toxicity displayed at the table. Out of 10 pts with measurable disease, 3 had a PR, 4 more had disease stabilization. Median PFS of all pts (5 censored) is 3.9+ (1–9.3+) mos. whereas median OS is not yet reached. Conclusion: TEX can safely be administered without higher graded toxicity in pts with GC. Preliminary efficacy results indicate promising activity that merits further testing in a phase II trial. [Table: see text]

[Table: see text]

Age Influences the Expression of GAP-43 in the Rat Hippocampus following Seizure

BACKGROUND

Normal aging is associated with impairments in learning and memory and motor function. One viable hypothesis is that these changes reflect an age-related decrease in brain plasticity.

OBJECTIVE

The aim of the present study was to identify age-related changes in the time course of expression of the axonal growth associated protein 43 (GAP-43) in a rat model of brain plasticity.

METHODS

We examined by Northern blotting, in situ hybridization, and immunohistochemistry the effects of age on the time course of the expression GAP-43 following pentylenetetrazole-induced seizure in the hippocampus of 3-, 18-, and 28-month-old rats.

RESULTS

In this model of brain plasticity, young rats displayed a decrease in GAP-43 mRNA levels in CA1, CA3, and polymorphic regions, lasting from 10 h to 3 days after seizure. This was followed by recovery, with peak expression between days 10 and 20. The baseline levels of GAP-43 mRNA decreased with age, especially in the CA3 region. Despite lower baseline levels, middle-aged rats showed the same pattern of upregulation of GAP-43 mRNA expression as the young animals. Old rats showed only minimal upregulation, however, and this occurred only in the polymorphic layer. The level GAP-43 protein itself was higher in old control rats than in the other two control groups, a condition that was transiently reversed by seizure activity.

CONCLUSIONS

Middle-aged rats are still capable of a sustained, though diminished, response to seizure activity, while old rats lose this ability. Disruption of the temporal and anatomical coordination of expression of GAP-43 may contribute to the general decline in brain plasticity with age.

Observations on experimental marginal periodontitis in rats

OBJECTIVE

The purpose of this study was to assess periodontal destruction following experimentally induced marginal periodontitis in rats by ligatures over a 60-day observation period. The extent to which the physiological movement of teeth influenced the effect of the ligatures was also examined. In addition, two methods for measuring bone loss in the defleshed jaw were compared.

METHODS

Thirty-five male Sprague-Dawley rats (SD) were divided into five groups. Marginal periodontitis was induced by ligatures on the second maxillary molars. Rats were killed after 15, 30, and 60 days. Rats in the control group were killed on day 1 and day 60. Bone loss was determined with two different methods on the buccal and palatinal surfaces of the defleshed jaw. In the first method, the distance of the cementoenamel junction (CEJ) from the alveolar bone crest (ABC) was measured at different sites; in the second method, the area of the exposed root surface of the molars was measured.

RESULTS

Comparison of the control groups from day 1 and day 60 using both measuring methods showed significant differences in bone loss. In the area where the ligature was located, test rats exhibited significantly greater bone loss than control rats. Comparison of control rats from day 1 with test rats from day 15 showed that the increase in bone loss between the groups within the area of the ligature was significantly greater than outside it. The age-dependent bone loss increases over the entire observation period of 60 days. The ligature-induced bone loss increased most from day 1 to day 15; on days 30 and 60, slighter increases in bone loss were observed.

CONCLUSIONS

The application of this model can only be recommended for short (</=15 days) observation periods. The distance method should be preferred to the area method.

Dynamics of gene expression for immediate early- and late genes after seizure activity in aged rats

The ability of the rodent brain to support plasticity-related phenomena declines with increasing age. A decreased coordination of genes implicated in brain plasticity may be one factor contributing to this decline. Synaptic rearrangement that occurs after seizure activity is regarded as a model of brain plasticity. In a rat model of seizure-related brain plasticity, we found that the induction of immediate-early genes, as exemplified by c-fos and tissue plasminogen activator ( tPA), is not impaired in the aged rat brain. However, the aged rat brain responded more slowly to chemically induced seizure, and the levels of c-fos and tPA mRNAs induction are decreased in the cortex and in the hippocampus of 30 month old rats, as compared to the levels expressed by 3 month old rats. In addition, at the peak induction, the TPA transcripts were restricted to certain cortical layers of the older rats. Surprisingly, in applying the same experimental paradigm to late genes, we found that there was a shift toward earlier times in the maximum expression of growth-related molecules, the microtubule-associated protein 1B (MAP1B) mRNA, which was very evident in 18 month old rats. Aberrant immunolabeling of MAP1B occurred in cortical layer VI of the aged rats where, unlike in young rats, there was heavy staining of neuronal somata. These results suggest that (1) one consequence of aging, besides decreases in the levels of mRNA, is a progressive loss of coordination in gene activity following the administration of a stimulus; (2) since c-fos, TPA and MAP1B have been implicated in neuronal plasticity, these findings could explain, in part, the limited plasticity of the aging brain.

Brain plasticity: to what extent do aged animals retain the capacity to coordinate gene activity in response to acute challenges

The ability of the rodent brain to support plasticity-related phenomena declines with increasing age. A decreased coordination of genes implicated in brain plasticity may be one factor contributing to this decline. Synaptic rearrangement that occurs after seizure activity is regarded as a model of brain plasticity. In a rat model of seizure-related brain plasticity, we found that the induction of immediate-early genes, as exemplified by c-fos and tissue plasminogen activator (TPA) is not impaired in the aged rat brain. However, the aged rat brain responded more slowly to chemically induced seizure and the levels of c-fos and TPA mRNAs induction are decreased in the cortex and in the hippocampus of 30-month-old rats, as compared to the levels expressed by 3-month-old rats. In addition, at the peak induction the TPA transcripts were restricted to certain cortical layers of the older rats. Surprisingly, in applying the same experimental paradigm to late genes we found that there was a shift toward earlier times in the maximum expression of growth-related molecule, the microtubule-associated protein 1B (MAP1B) mRNA, which was very evident in 18-month-old rats. Aberrant immunolabeling of MAP1B occurred in cortical layer VI of the aged rats where, unlike in young rats, there was heavy staining of neuronal somata. These results suggest that (i) one consequence of aging, besides decreases in the levels of mRNA, is a progressive loss of coordination in gene activity following the administration of a stimulus; (ii) since c-fos, TPA and MAP1B have been implicated in neuronal plasticity, these findings could explain, in part, the limited plasticity of the aging brain.

Delayed and blunted induction of mRNA for tissue plasminogen activator in the brain of old rats following pentylenetetrazole-induced seizure activity

The ability of the rodent brain to support plasticity-related phenomena declines with increasing age. Here we investigated the extent to which old rats retain the capacity to initiate transcription for immediate early genes, particularly as it relates to brain plasticity, in response to a strong stimulus. The intraperitoneal administration of pentylenetetrazole (PTZ) to rats of various ages evoked tonic-clonic seizures. Using an RNA gel-blot and in situ hybridization analysis, we found that 1 hour after the onset of seizure, messenger RNA (mRNA) for tissue plasminogen activator (TPA) was increased approximately 3.7-fold in the hippocampi of 3-month-old rats. The levels of TPA mRNA in the hippocampi and cortices of 3-month-old rats returned to control levels by 3 hours after PTZ administration. The levels of TPA mRNA increased 2.5-fold in the hippocampi of 18-month-old rats and 1.8-fold in the brains of the 28-month-old-rats at 3 hours and returned to basal levels by 15 hours following PTZ treatment. Quantitatively similar increases were calculated for the cortex. At peak induction the transcripts were localized throughout the cortical layers of the 3-month-old rats, whereas the TPA mRNA expression was restricted to cortical layer V of the older rats. Our results suggest that although the aging brain retains the capacity to respond to chemically induced seizures, the induction of TPA mRNA is temporarily delayed and the levels are diminished with increasing age. Because TPA has been implicated in neuronal plasticity, this finding suggests that immediate early genes are important factors in the limited plasticity of the aging brain.

Anomalous expression of microtubule-associated protein 1B in the hippocampus and cortex of aged rats treated with pentylenetetrazole

The aim of the present study was to assess the age-dependent response of microtubule-associated protein 1B, a plasticity-associated protein deriving from a late gene, following administration of an epileptogenic stimulus. The effect of a single administration of the convulsant pentylenetetrazole on microtubule-associated protein 1B expression in the hippocampal formation and cortex of three-, 18- and 28-month-old rats was assessed using northern blot analysis, in situ hybridization and immunohistochemistry. In three-month-old rats, we detected initial increases in microtubule-associated protein 1B messenger RNA at 15 h following pentylenetetrazole administration in the granule cells of the dentate gyrus, in the CA3 region of the hippocampus and in layers II/III of the entorhinal cortex, and these reached a maximum at 44 h. However, in the hippocampus and cortex of 18-month-old rats, the peak occurred at 15 h, and in the brains of 28-month-old rats a blunted peak was reached at 3 h. Pentylenetetrazole treatment in young rats resulted in a robust induction of microtubule-associated protein 1B immunoreactivity in the granule cells of the dentate gyrus and in layers II/III of the entorhinal cortex, but also produced a large decrease in the retrosplenial cortex. However, following pentylenetetrazole treatment in older rats, the granule cells of the dentate gyrus were nearly devoid of microtubule-associated protein 1B immunoreactivity, whereas the retrosplenial cortex showed no changes at all, and the entorhinal cortex had an expression pattern similar to that of young rats. Aberrant immunolabeling of microtubule-associated protein 1B occurred in cortical layer VI of the aged rats where, unlike in young rats, there was heavy staining of neuronal somata. These results suggest that the regulation of the plasticity-associated protein microtubule-associated protein 1B is altered in the ageing rat brain, with the peak of expression shifted to earlier times in 18-month-old rats and blunted, variable increases at even earlier times in 28-month-old rats.

Upregulation of MAP1B and MAP2 in the rat brain after middle cerebral artery occlusion: effect of age

Although stroke in humans usually afflicts the elderly, most experimental studies on the nature of cerebral ischemia have used young animals. This is especially important when studying restorative processes that are age dependent. To explore the potential of older animals to initiate regenerative processes after cerebral ischemia, the authors studied the expression of the juvenile-specific cytoskeletal protein, microtubule-associated protein (MAP) 1B, and the adult-specific protein, MAP2, in male Sprague-Dawley rats at 3 months and 20 months of age. The levels of MAP1B and MAP2 transcripts and the corresponding proteins declined with increasing age in the hippocampus. In the cortex, the levels of the transcripts did not change significantly with age, but the morphologic features of immunostained fibers were clearly affected by age; that is, cortical MAP1B fibers became thicker, and MAP2 fibers, more diffuse, in aged rats. Focal cerebral ischemia, produced by reversible occlusion of the right middle cerebral artery, resulted in a large decrease in the expression of both MAP1B and MAP2 in the infarct core at the messenger ribonucleic acid and protein levels. However, at 1 week after the stroke, there was vigorous expression of MAP1B and its messenger ribonucleic acid, as well as MAP2 protein, in the border zone adjacent to the infarct of 3-month-old and 20 month-old male Sprague-Dawley rats. The upregulation of these key cytologic elements generally was diminished in aged rats compared with young animals, although the morphologic features of fibers in the infarct border zone were similar in both age groups. These results suggest that the regenerative potential of the aged rat brain appears to be competent, although attenuated, at least with respect to MAP1B and MAP2 expression up to 20 months of age.

Altered expression of microtubule-associated protein 1B in cerebral cortical structures of pentylenetetrazole-treated rats

Using Northern blot, immunoblotting, immunocytochemistry, and in situ hybridization, we show that a single administration of the convulsant pentylenetetrazole leads to robust, long-term changes in microtubule-associated protein 1B and its mRNA, in the adult rat brain. The first increases in MAP1B mRNA were detected at 15 hr following pentylenetetrazole administration in the temporal (Te2) and perirhinal cortex followed by increases in microtubule-associated protein 1B immunoreactivity at 72 hr postseizure. In contrast, the levels of microtubule-associated protein 1B mRNA and protein in layers I-II of the retrosplenial and parietal cortex (Par2) declined visibly by 24 hr and 72 h, respectively, post-seizure. The changes included loss of staining in layers I-II and development of structures resembling "strings-of-beads" along the fibers of projection neurons of layer V. The levels of microtubule-associated protein 1B mRNA in the entorhinal cortex peaked at later times (72 h), especially in layers II-III, and returned to control levels by 10 days. Whereas the levels of microtubule-associated protein 1B immunoreactivity in the retrosplenial and parietal cortex recovered by 5-10 days, it persisted at high levels through day 35 in layer V of the temporal cortex (Te2), layers II-III of the perirhinal cortex and layers I-II of the lateral entorhinal cortex. These results indicate that seizure activity leads to long-term upregulation of genes coding for structural elements that are characteristic of the immature brain such as microtubule-associated protein 1B.

Increased expression of microtubule-associated protein 1B in the hippocampus, subiculum, and perforant path of rats treated with a high dose of pentylenetetrazole

A single administration of the convulsant pentylenetetrazole (PTZ) initiates a complex pattern of long-term changes in microtubule-associated protein 1B (MAP1B) expression across the hippocampal formation. Using Northern blot and in situ hybridization we show that the first increases in MAP1B mRNA were detected at 15 h following PTZ administration in the granule cells of the dentate gyrus and CA3 region of the hippocampus and reached a maximum at 44 h. The levels of MAP1B mRNA in the subiculum peaked at later times (5 days). At 72 h MAP1B immunoreactivity was mainly localized in the granule-cell bodies and dentate inner and midmolecular layer as well as in neuronal cell bodies and the stratum lucidum, including the mossy fiber pathway of the CA3 region. By 5-10 days the levels of MAP1B in the pyramidal cells in the CA3 region decreased to very low levels; rather, heavy staining of interneuron-like cells and "strings-of-bead" structures all over the hippocampus and at the stratum oriens/alveus border were seen. The levels of MAP1B in the hippocampus returned to control levels by 20 days after PTZ administration. MAP1B immunoreactivity in the alvear path was also evident at 5 days postinjection at the CA1/alveus border. The intensity of MAP1B staining increased gradually in the perforant path starting at 72 h and persisted at high levels until day 35. Our studies show that (i) MAP1B is a temporal and regional marker for rapid and acute epileptic seizures and (ii) long-term increases in MAP1B in the perforant path might play a role in PTZ-induced seizures.