A polymorphism of the XRCC1 gene predicts for response to platinum based treatment in advanced colorectal cancer

Recently, it has been demonstrated that the Arg399Gln substitution in the XRCC1 gene is associated with increased levels of markers of DNA damage. Deficiency in DNA repair pathways has been shown to confer to resistance to several drugs, including platinum compounds. Here we have studied whether this polymorphism of the XRCCI gene will predict response and survival of patients with metastatic colorectal cancer treated with oxaliplatin and 5-FU. Sixty-one patients received a combination of 130 mg/m2 oxaliplatin and continuous infusion 5-FU. The XRCC1 polymorphism was evaluated using a RFLP method. We found 73% (8/11) of responders had an Arg/Arg genotype and three were heterozygous, but 66% (33/50) of non-responders showed a Gln/Gln or Gln/Arg genotype (p=0.038). Patients carrying at least one Gln mutant allele were at a 5.2 (95%CI: 1.21,22.07) fold increased risk to fail the 5-FU/oxaliplatin chemotherapy. The data suggest that the polymorphism in exon 10 of the XRCC1 gene may be associated with resistance to oxaliplatin/5-FU chemotherapy in advanced colorectal cancer.

Phase II trial of outpatient schedule of paclitaxel in patients with previously untreated metastatic, measurable adenocarcinoma of the stomach

BACKGROUND

Chemotherapy represents the standard treatment for patients with metastatic stomach cancer. Conflicting results have been published regarding the activity of paclitaxel in this setting. Therefore, we developed a phase II study to evaluate an outpatient 3 h infusion of paclitaxel.

METHODS

Patients with chemonaive metastatic stomach cancer received paclitaxel 210 mg/m(2) every 3 weeks. Patients with esophageal cancer were not eligible.

RESULTS

Twenty-one patients were enrolled. The median age was 55.5 years (range 37-81 years). Two partial responses were observed among the 18 patients evaluable for response and toxicity (response rate 11%, 95% CI: 2-33%). The median time to progression was 10.5 weeks and median survival 23 weeks. There was only one episode of grade IV neutropenia and no episodes of grade 3-4 non-hematological toxicity were observed.

CONCLUSION

Paclitaxel exhibited minimal activity in this patient population.

Sensitive and reproducible quantitation of mucosal HIV-1 RNA and DNA viral burden in patients with detectable and undetectable plasma viral HIV-1 RNA using endoscopic biopsies

Mucosal tissue is the main portal of entry for HIV-1 infection and, in macaques, has been demonstrated to be a significant compartment for viral replication and CD4+ T lymphocyte depletion. Quantitating tissue viral burden in addition to plasma viral load provides insights into HIV-1 pathogenesis and an additional means to gauge antiretroviral response. The aim of this study was to develop reliable, reproducible, and sensitive assays to quantitate tissue viral burden of HIV-1 RNA and DNA using 1-3 endoscopically acquired, rectosigmoid biopsies. Total DNA and RNA were simultaneously extracted following homogenization from the same tissue samples. Quantitative polymerase chain reaction (PCR) assay in the HIV-1 LTR region was used to detect viral DNA and RT-PCR for viral RNA. It was determined that HIV-1 RNA and DNA can be reproducibly quantified from a single rectosigmoid biopsy with minimal intra-assay or intra-patient variability. These results reflect high recovery of extracted nucleic acids with calculated results accurately reflecting in vivo levels. The techniques outlined differ from currently available approaches by incorporating control standards to identify loss or degradation of RNA and DNA from acquisition through the in vitro assay and permit extraction with high yields of RNA and DNA from the same tissue sample.

Phase I trial of 96-hour continuous infusion of dexrazoxane in patients with advanced malignancies

Dexrazoxane is a bidentate chelator of divalent cations. Pretreatment with short infusions of dexrazoxane prior to bolus doxorubicin has been shown to lessen the incidence and severity of anthracycline-associated cardiac toxicity. However, because of rapid, diffusion-mediated cellular uptake and the short plasma half-life of dexrazoxane, combined with prolonged cellular retention of doxorubicin, dexrazoxane may be more effective when administered as a continuous infusion. Thus, a Phase I pharmacokinetic trial of a 96-h infusion of dexrazoxane was performed. Dexrazoxane doses were escalated in cohorts of 3 to 6 patients per dose level. All patients received granulocyte-colony stimulating factor at a dose of 5 microg/kg/day starting 24 h after completion of the dexrazoxane infusion. Plasma samples were collected and analyzed for dexrazoxane by high-performance liquid chromatography. Urine collections were performed at baseline and during the infusion to determine the renal clearance of dexrazoxane and the excretion rate of divalent cations. Twenty-two patients were enrolled at doses ranging from 125 to 250 mg/m(2)/day. Grade 3 and 4 toxicities included grade 4 thrombocytopenia in 2 patients treated at 250 mg/m(2)/day, grade 3 thrombocytopenia and grade 4 nausea and vomiting in 1 patient treated at 221 mg/m(2)/day, grade 4 diarrhea and grade 3 nausea and vomiting in 1 patient treated at 221 mg/m(2)/day, and grade 3 hypertension in 1 patient treated at 166.25 mg/m(2)/day. Steady-state dexrazoxane levels ranged from 496 microg/l (2.2 microM) to 1639 microg/l (7.4 microM). Dexrazoxane plasma CL(ss) and elimination t(1/2) were 7.2 +/- 1.6 l/h/m(2) and 2.0 +/- 0.8 h, respectively. The mean percentage of administered dexrazoxane recovered in the urine at steady state was 30% (range, 10-66%). Urinary iron and zinc excretion during the dexrazoxane infusion increased in 12 of 18 and 19 of 19 patients by a median of 3.7- and 2.4-fold, respectively. These results suggest that dexrazoxane as a 96-h infusion can be safely administered with granulocyte-colony stimulating factor at doses that achieve plasma levels that have been demonstrated previously to inhibit topoisomerase II activity and to induce apoptosis in vitro. Additional studies will be required to determine whether the combination of continuous infusions of dexrazoxane and doxorubicin would provide enhanced cardioprotection compared with the currently recommended bolus or short infusion schedules.

Determinants of prognosis and response to therapy in colorectal cancer

Identification of the molecular determinants of 5-fluorouracil (5-FU) and irinotecan (CPT-11) efficacy and toxicity is critically important for the development of more efficient and less toxic treatment strategies for patients with colon cancer. We have identified molecular predictors of response to chemotherapy with 5-FU and survival in patients with advanced colorectal cancer. Low gene expression levels of thymidylate synthase (TS), dihydropyrimidine dehydrogenase (DPD), and thymidine phosphorylase (TP) are associated with response and survival. Preliminary data suggest that gene expression levels of topoisomerase I, p21, bcl-2, and ICE may be predictive of response to therapy with CPT-11. Increased toxicity seen in patients treated with CPT-11 may be explained by polymorphism in the UGT1A1 gene, which is responsible for glucuronidation of the active metabolite of CPT-11.

[Molecular markers as basis for chemotherapy?]

Although a majority of cancer patients show no response or minimal response to any given chemotherapy, all patients are nevertheless placed on standard therapy regimens because there has been no way to identify beforehand those patients who are destined not to respond. Determining the biochemical factors relevant to drug response in each patient's tumor cells prior to treatment should allow optimal therapy to be selected for each patient on a rational basis. In this paper, we summarize studies aimed at determining whether analysis of the quantitative expression levels of genes or proteins involved in cancer drug activity in clinical specimens of tumor tissue could predict the effect of the drug on a tumor. This hypothesis has been tested mostly in 5-fluorouracil (5-FU)-based regimens in colorectal cancer. In the case of 5-FU, the quantitative expression levels of thymidylate synthase, thymidine phosphorylase, and dihydropyrimidine dehydrogenase were found to be associated with tumor response. Using all three of these markers together resulted in very effective identification of responding patients. The salient results of these studies were that, using the PCR enhanced by newly developed methodology, gene expressions can be identified and measured in pretreatment biopsies that are quantitatively associated with either response or non-response to drugs that are used in treating colorectal cancer.

dUTP nucleotidohydrolase isoform expression in normal and neoplastic tissues: association with survival and response to 5-fluorouracil in colorectal cancer

Aberrant dUTP metabolism plays a significant role in the underlying molecular mechanisms of cell killing mediated by inhibitors of thymidylate biosynthesis. dUTP nucleotidohydrolase (dUTPase) is the key regulator of dUTP pools, and significant evidence exists suggesting that the expression of this enzyme may be an important determinant of cytotoxicity mediated by inhibitors of thymidylate synthase (TS). In this study, we have determined the expression patterns of dUTPase in normal and neoplastic tissues and examined the association between dUTPase expression and response to 5-fluorouracil (5-FU)-based chemotherapy and overall survival in colorectal cancer. Immunohistochemistry was performed on formalin-fixed, paraffin-embedded tissue sections using a monoclonal antibody (MAb), DUT415, that cross-reacts with both nuclear and mitochondrial isoforms of human dUTPase. Nuclear and cytoplasmic staining was observed in both normal and neoplastic tissues. In normal tissues, nuclear dUTPase staining was observed exclusively in replicating cell types. This observation is in agreement with cell culture studies where expression of the nuclear isoform (DUT-N) is proliferation dependent In contrast, cytoplasmic expression of dUTPase does not correlate with proliferation status and was observed in tissues rich in mitochondria. Consistent with this observation, cell culture studies reveal that the mitochondrial isoform (DUT-M) is expressed constitutively, independent of cell cycle status. These data suggest that in normal tissues, nuclear staining with the DUT415 antibody represents the DUT-N isoform, whereas cytoplasmic staining represents the DUT-M isoform. In colon cancer tumor specimens, expression of dUTPase was shown to be highly variable in both amount and intracellular localization. Patterns of dUTPase protein expression observed included exclusive nuclear, exclusive cytoplasmic, and combined nuclear and cytoplasmic staining. Thus, immunohistochemical detection of dUTPase in colon cancers provides distinct intracellular phenotypes of expression that may be of significant prognostic value. To examine the association between dUTPase expression and response to 5-FU-based chemotherapy and overall survival, we initiated a retrospective study including tumor specimens from 20 patients who had received protracted infusion of 5-FU and leucovorin for treatment of metastatic colon cancer. Positive nuclear staining was found in 8 patients, whereas 12 lacked nuclear expression. Of the patients lacking nuclear dUTPase expression, 6 responded to 5-FU-based chemotherapy, 4 had stable disease, and 2 had progressive disease. Of the patients presenting positive nuclear dUTPase expression, 0 responded to chemotherapy, 1 had stable disease, and 7 had progressive disease (P = 0.005). The median survival for patients with tumors lacking nuclear staining was 8.5 months and 6.9 months for patients with tumors demonstrating positive nuclear dUTPase expression (P = 0.09). Time to progression was significantly longer for patients with tumors lacking nuclear staining (P = 0.017). Variable cytoplasmic dUTPase expression was observed in these tumors; however, there was no apparent association with clinical response or survival in this limited study. Nuclear dUTPase staining within these tumors was also associated with TS gene expression (P = 0.06). This study demonstrates that low intratumoral levels of nuclear dUTPase protein expression is associated with response to 5-FU-based chemotherapy, greater time to progression, and greater overall survival in colorectal cancer. Conversely, high levels of nuclear dUTPase protein expression predict for tumor resistance to chemotherapy, shorter time to progression, and shorter overall survival. This report represents the first clinical study implicating dUTPase overexpression as a mechanism of resistance to TS inhibitor-based chemotherapy.

Colorectal tumors responding to 5-fluorouracil have low gene expression levels of dihydropyrimidine dehydrogenase, thymidylate synthase, and thymidine phosphorylase

We had previously shown that high gene expressions (mRNA levels) of thymidylate synthase (TS; Leichman et al., J. Clin. Oncol., 15: 3223-3229, 1997) and thymidine phosphorylase (TP; Metzger et al., Clin. Cancer Res., 4: 2371-2376, 1998) in pretreatment tumor biopsies could identify tumors that would be nonresponsive to 5-fluorouracil (5-FU)-based therapy. In this study, we investigated the association between intratumoral gene expression of the pyrimidine catabolism enzyme dihydropyrimidine dehydrogenase (DPD) and the response of colorectal tumors to the same 5-FU-based protocol. DPD expressions were measured by quantitative reverse transcription-PCR in 33 pretreatment biopsies of colorectal tumors from patients who went on to receive treatment with 5-FU and leucovorin (LV). The range of DPD gene expression in those tumors that were nonresponsive to 5-FU was much broader than that of the responding tumors. None of the tumors with basal-level DPD expressions above a DPD:beta-actin ratio of 2.5 x 10(-3) (14 of 33) were responders to 5-FU/LV therapy, whereas those tumors with DPD gene expressions below DPD: beta-actin ratio of 2.5 x 10(-3) had a response rate of 50%. There was no correlation among DPD, TS, and TP expression values in this set of colorectal tumors, which indicated that these gene expressions are independent variables. All of the tumors that responded to 5-FU therapy (11 of 33) had expression values of all three of the genes, TS, TP, and DPD, below their respective nonresponse cutoff values, whereas, in each of the nonresponding tumors, at least one of these gene expressions was high. The patients with low expression of all three of the genes had significantly longer survival than patients with a high value of any one of the gene expressions. The results of this study show that intratumoral gene expression level of DPD is associated with tumor response to 5-FU and that the use of more than one independent determinant of response permits the identification of a high percentage of responding patients.

High basal level gene expression of thymidine phosphorylase (platelet-derived endothelial cell growth factor) in colorectal tumors is associated with nonresponse to 5-fluorouracil

The gene expression levels of the nucleoside cleavage enzyme/angiogenic factor thymidine phosphorylase (TP), also known as platelet-derived endothelial cell growth factor, were measured by quantitative reverse transcription-PCR in 38 pretreatment biopsies of colorectal tumors from patients who were subsequently treated with 5-fluorouracil (5-FUra) and leucovorin (LV). The range of TP gene expression (relative mRNA levels) in those tumors nonresponsive to 5-FUra was much broader than that of the responding tumors. In contrast to in vitro studies that had shown that an increased intracellular level of TP potentiates the activity of 5-FUra by converting it to the more cytotoxic nucleoside form 5-fluoro-2'deoxyuridine, tumors with the highest basal TP expressions were nonresponders to 5-FUra/LV therapy. The mean TP mRNA level in the nonresponding tumors was 2.6-fold higher than that of the responding patients. We had shown previously that high expression of thymidylate synthase (TS), the target enzyme of 5-FUra, was also a predictor of nonresponse to 5-FUra (L. Leichman et al, J. Clin. Oncol., 15: 3223-3229, 1997). TP and TS expressions were found to be independent variables in these tumors, so that low expression levels of both TS and TP in tumors predicted a very high response rate (11 of 14) to 5-FUra/LV as well as a significantly longer survival, whereas none (0 of 24) of the patients with high expression of either TP or TS were responders.

Desensitization and sensitization of cells to fluoropyrimidines with different antisenses directed against thymidylate synthase messenger RNA

Previous studies have shown that the cytotoxicity of fluoropyrimidines is mediated, in large part, by inhibition of the enzyme thymidylate synthase (TS). The aim of this study was to determine whether the chemosensitivity of human cancer cells to fluoropyrimidines could be increased by decreasing TS expression with antisense oligodeoxyribonucleotides (ODNs). ODNs (18-mers) targeted at the AUG translational initiation site of TS mRNA inhibited translation in a sequence- and dose-dependent manner in a rabbit reticulocyte lysate in vitro translation system. Treatment of human colon cancer HT-29 cells with antisense ODNs decreased TS catalytic activity in the cells in a dose-dependent manner over a short period, but the longer-term effect of the TS antisense ODN treatment was actually to increase the amount of TS in the cells and to decrease their sensitivity to 5-fluoro-2'-deoxyuridine (FdUrd). However, when human nasopharyngeal cancer KB31 cells were transfected with a plasmid (pHaMAGRP) construct containing the TS antisense fragment (+ 1 to + 422) under the control of a glucose-regulated promoter, the expression of both TS protein and TS catalytic activity was decreased by nearly 30% (P = 0.014), and sensitivity of these cells to FdUrd was enhanced by approximately 8-fold (P = 0.021). No changes in the levels of expression of TS protein or FdUrd-associated cytotoxicity were observed in control, vector-transfected cells. No change was observed in the sensitivity of transfected cells toward either cisplatin or Adriamycin. These results show that the level of expression of TS in human malignant cells can be down-regulated with antisense TS RNA, and their sensitivity to fluoropyrimidines can, thereby, be increased.

p53 point mutations and thymidylate synthase messenger RNA levels in disseminated colorectal cancer: an analysis of response and survival

Recent studies suggest that there may be a strong correlation between the p53 status of a tumor and a patient's response to chemotherapy. Therefore, we determined p53 status in 36 patients with disseminated colorectal cancer by cDNA sequencing and immunohistochemical staining, as well as by the gene expression level of thymidylate synthase (TS), the target enzyme of 5-fluorouracil (5-FU), by reverse transcription-PCR. Ten patients (28%) experienced a clinical response to 5-FU chemotherapy. Overall, TS expression and response to chemotherapy were associated: 9 of 18 (50%) patients with TS < or = 3.0 x 10(-3) responded, compared to 1 of 18 (6%) patients with TS > 3.0 x 10(-3) (P = 0.003). p53 mutations were found in 21 of 36 patients (58%) using cDNA cycle sequencing, and p53 protein overexpression was found in 20 of 32 patients (62%) using immunohistochemistry staining. Overall p53 status and response to chemotherapy were associated: 5 of 10 (50%) patients with wild-type p53 or negative p53 staining experienced a response, but only 5 of 26 (19%) patients with mutant p53 or p53 overexpression responded. TS expression, but not expression of p53, was significantly associated with overall survival (P = 0.002). Patients with wild-type p53 had significantly lower TS levels compared to patients with mutated p53 (P = 0.044). In this study, we also present data linking specific p53 point mutations to TS expression levels and resistance to 5-FU. Although the number of patients is relatively small, these results identify p53 status and TS gene expression as associated with response in disseminated colorectal cancer; independent studies are needed to confirm these findings and to provide information leading to a better understanding of the role of 5-FU-based chemotherapy in the treatment of colorectal cancer.

p53 and thymidylate synthase expression in untreated stage II colon cancer: associations with recurrence, survival, and site

We initiated a retrospective study to determine whether p53 status and thymidylate synthase (TS) protein expression in primary colon tumors influence recurrence and survival for patients with stage II colon cancer. Tumor specimens from 45 consecutive untreated patients with stage II colon cancer were examined for p53 and TS protein expression using immunohistochemistry. The median follow-up was 5.1 years. Eighteen patients had left-sided tumors, and 27 had right-sided tumors. Fourteen of 45 patients (31%) developed recurrence. p53 overexpression was detected in the tumors of 18 patients (40%); 10 patients (55%) with p53 overexpression recurred; and 4 of 27 (15%) without evidence of p53 overexpression recurred (P = 0.002). High TS expression was detected in the tumors of 16 patients (36%): 8 patients (50%) with high TS expression recurred, and 6 patients (21%) with low TS expression recurred (P = 0.027). Patients with p53 overexpression had a significantly poorer survival than did those patients without p53 overexpression (P < 0.001). High TS expression was associated with poor survival (P = 0.004). p53 overexpression and high TS expression were significantly associated with left-sided tumors (P = 0.003 and P = 0.022). Thirteen of 16 patients (81%) with high TS expression also overexpressed p53, and 24 of 29 patients (81%) with low TS expression did not manifest p53 overexpression (P < 0.001). p53 and TS expression in primary stage II colon cancer are associated and appear to influence recurrence and survival. In this pilot study, left-sided tumors demonstrate significantly more p53 overexpression and significantly higher TS expression than do right-sided tumors, which may explain the significantly poorer survival for patients with left-sided tumors.

Restoration of wild-type p53 activity in p53-null HL-60 cells confers multidrug sensitivity

HL-60 cells that stably express transfected wild-type (wt) p53 were used to determine whether restoration of wt p53 increased the chemosensitivity of cells that normally lack p53 activity. The wt p53 HL-60 transfectants (SN3 cells) were more sensitive than the parental (S) cells to a number of common anticancer drugs representing various mechanisms of action, whereas HL-60 cells transfected with p53 genes mutated at codons 248 and 143 were not sensitized. The sensitization ratio due to the transfected wt p53 varied from about 2-fold for cisplatin to over 50-fold for thymidine. Cells treated with the thymidylate synthase inhibitor 5-fluoro-2'-deoxyuridine (FdUrd) were used to study changes in various p53-associated gene expressions. A higher percentage of apoptotic cells among the SN3 cells was observed than among the S cells at each concentration of FdUrd. The S cells had undetectable levels of bax and high levels of bcl-2, whereas the SN3 cells had undetectable levels of bcl-2 levels and appreciable basal levels of bax. After FdUrd treatment of SN3 cells, both p53 and bax levels increased, but the induction of bax was faster than that of p53 and paralleled the appearance of apoptotic DNA laddering. FdUrd treatment induced p21 expression and increased the G1 fraction of the SN3 cells but did not induce p21 or change the phase distribution in the S cells. FdUrd treatment also induced the expression and phosphorylation of cyclin D1 in the SN3 cells but not in the S cells. These results show that transfected wt p53 confers multidrug sensitivity to HL-60 cells by re-adjustment of the expressions of apoptosis genes and displays other properties characteristic of endogenously originated wt p53.

Intercellular communication mediates the bystander effect during herpes simplex thymidine kinase/ganciclovir-based gene therapy of human gastrointestinal tumor cells

A bystander effect is described when nontransduced or genetically unmodified cells are killed during death of genetically modified tumor cells transduced with a suicide gene. The "bystander effect" greatly enhances the efficacy of the herpes simplex virus-thymidine kinase/ganciclovir (HSV-TK/GCV) gene therapy approach for cancer. The mechanism of the bystander effect is controversial. In this study, we examined the role of intercellular gap junction communication (GJIC) for the bystander effect in human gastrointestinal tumor cells. Our results show that the extent of the bystander effect varied amongst the tumor cell lines; pancreatic cancer cells BXPC-3 exhibited excellent bystander effects in vitro and in vivo studies whereas other gastrointestinal tumor cell lines such as pancreatic cancer cells MIAPACA-2, and colon cancer cells HT-29 showed poor bystander effects. Bystander effects were only found in the presence of cell-to-cell contact. The extent of the bystander effect was independent of the level of HSV-TK activity in the transduced tumor cells and was correlated with GJIC as demonstrated by an in vitro dye-transfer assay. Expression of the mRNA levels of gap junction protein connexin 43 was 8- to 26-fold or greater and connexin 26 gene expression was 2- to 229-fold greater in BXPC-3 cells compared to HT-29, MIAPACA-2, and PANC3 cells. Our results suggest that intercellular communication is essential for the bystander effect. The correlation between GJIC and the extent of the bystander effect suggest a role for GJIC in mediating the bystander effect. Analysis of tumors for GJIC or expression of gap junction proteins may identify the subset of patients suitable for gene therapy with the HSV-TK/GCV approach.

ERCC1 mRNA levels complement thymidylate synthase mRNA levels in predicting response and survival for gastric cancer patients receiving combination cisplatin and fluorouracil chemotherapy

PURPOSE

We have previously shown that relative thymidylate synthase (TS) mRNA levels in primary gastric adenocarcinomas treated with fluorouracil (5-FU) and cisplatin are inversely associated with response and survival. This is a presumed function of TS as a target for 5-FU activity. We now test the hypotheses that the relative mRNA level of the excision repair cross-complementing (ERCC1) gene is inversely associated with response and survival as an independent function of cisplatin efficacy.

PATIENTS AND METHODS

Patients had intact, untreated, primary gastric adenocarcinoma cancer and were evaluated for eligibility on a preoperative cisplatin infusion-5-FU protocol. cDNA, derived from primary gastric tumors before chemotherapy, was used to determine ERCC1 mRNA levels, expressed as the ratio of polymerase chain reaction (PCR) product of the ERCC1 gene and the beta-actin gene.

RESULTS

The median ERCC1 mRNA level from 38 primary gastric cancers (33 assessable for response) was 5.8 x 10(-3) (range, 1.8 x 10(-3) to 19.5 x 10(-3)). Of 17 responding patients, 13 (76%) were less than or equal to 5.8 x 10(-3) and four were greater than 5.8 x 10(-3) (P = .003). The median survival for patients with ERCC1 mRNA levels less than or equal to 5.8 x 10(-3) has not been reached, whereas for those greater than 5.8 x 10(-3) it was 5.4 months (P = .034). The median TS mRNA level, 3.7 x 10(-3) (range, 0.9 to 18.9) also segregated responsive versus resistant tumors (P = .024). With both ERCC1 and TS mRNA levels below their medians, 11 of 13 patients (85%) responded; with both ERCC1 and TS mRNA levels above their medians, two of 10 patients (20%) responded (P = .003).

CONCLUSION

Considered separately, either ERCC1 or TS mRNA levels in a primary gastric adenocarcinoma has a statistically significant relationship to response. ERCC1 mRNA levels have a statistically significant association with survival; in this cohort TS mRNA levels did not reach statistically significant association with survival as in our previous publication. Whether these molecular parameters are independent of each other as predictors of outcome remains to be determined.

Quantitation of intratumoral thymidylate synthase expression predicts for disseminated colorectal cancer response and resistance to protracted-infusion fluorouracil and weekly leucovorin

PURPOSE

Response rates to fluorouracil (5-FU)-based therapy remain low. As new, active agents are being tested, information regarding specific intratumoral genetic determinants of chemotherapy sensitivity or resistance can be used to plan therapy rationally. Intratumoral thymidylate synthase (TS) quantitation may be among the most important determinants of sensitivity or resistance to 5-FU.

MATERIALS AND METHODS

Forty-six disseminated colorectal cancer patients had measurable tumor biopsies for polymerase chain reaction (PCR)-based determination of TS mRNA pretreatment. Protracted infusion of 5-FU 200 mg/m2/d for 21 days with weekly intravenous leucovorin 20 mg/m2 each cycle was given. After two cycles, responses were evaluated. Response data were correlated with independently determined intratumoral ratios of TS/beta-actin mRNA for each patient.

RESULTS

TS/beta-actin ratios were successfully obtained for 42 patients (91%). TS/beta-actin ratios ranged from 0.3 x 10(-3) to 18.2 x 10(-3) (median, 3.5 x 10[-3]). Twelve patients (26%) responded to treatment (median TS/beta-actin ratio, 1.7 x 10[+3]). Thirty-four patients did not respond (median TS/beta-actin ratio, 5.6 x 10[-3]). No patient with a TS mRNA level greater than 4.1 x 10(-3) responded. The median TS/beta-actin ratio (3.5 x 10[-3]) significantly segregated responders from nonresponders (P = .001). Median survival for patients with TS/beta-actin ratios < or = 3.5 x 10(-3) was 13.6 months; for patients with TS/beta-actin ratios greater than 3.5 x 10(-3), it was 8.2 months (P = .02).

CONCLUSION

For this cohort, the intratumoral TS/beta-actin ratio had a statistically significant association with response and survival. This relationship for other 5-FU schedules remains unknown. Confirmation of these data in a larger patient population could lead to determination of therapy for disseminated colorectal cancer based on a specific intratumoral molecular parameter.

High frequency of simultaneous loss of p16 and p16beta gene expression in squamous cell carcinoma of the esophagus but not in adenocarcinoma of the esophagus or stomach

Quantitative reverse transcription PCR (RT-PCR) was used to measure gene expressions (relative mRNA levels) of p16 and the alternate transcript pl6beta in esophageal and gastric tumors. p16 gene expression was undetectable in 13 of 25 esophageal squamous cell carcinomas. In 11 of these tumors, pl6beta was simultaneously missing whereas two of the pl6-deficient tumors still expressed p16beta. Among 34 esophageal adenocarcinomas and 11 gastric adenocarcinomas, only one tumor lacked p16 expression and all tumors expressed p16beta. p16 sequences were not detectable by PCR in genomic DNA from tumors lacking both p16 and p16beta mRNA, suggesting that the simultaneous loss of both gene expressions resulted from homozygous genomic deletion of the p16 gene. However, DNA from tumors that lacked p16 mRNA but expressed pl6beta did contain the p16 gene, consistent with loss of p16 expression in these tumors by transcriptional suppression. No point mutations in p16 cDNA were detected among 12 that were sequenced, but one p16 cDNA from a squamous cell carcinoma had a 19-base deletion, possibly indicating a splice-site mutation. Among those tumors that expressed p16 mRNA, the gene expression values of both p16 and pl6beta varied over a wide range. In some cases, p16 expression was detectable but low, suggesting that down-regulation of p16 expression may be used in some cases to achieve the funtional equivalent of gene deletion or transcriptional silencing. These results demonstrate that p16 expression patterns differ based on tumor histology and origin. Homozygous deletion of p16 appears to be common in esophageal squamous cell carcinomas but in adenocarcinomas, both gene deletion and transcriptional silencing of p16 were infrequent.

Thymidylate synthase is a predictor for response and resistance in hepatic artery infusion chemotherapy

The value of intratumoral thymidylate synthase (TS) quantitation as a predictive parameter for hepatic artery infusion (HAI) chemotherapy in patients with colorectal liver metastases was investigated. Relative TS mRNA levels were determined in 29 tumor samples using a quantitative RT-PCR amplification method. The median level of expression was 3.0 x 10(-3) (no units) and varied considerably among the tumors over a range of 135-fold. Patients with low TS levels were 4.1-fold more likely to respond (P < 0.03) compared to patients with high TS levels. Our results indicate that TS quantitation is a valuable predictive marker for tumor response to HAI therapy.

Thymidylate synthase mRNA level in adenocarcinoma of the stomach: a predictor for primary tumor response and overall survival

PURPOSE

We tested the hypothesis that polymerase chain reaction (PCR) quantitation of the enzyme thymidylate synthase (TS) within a primary adenocarcinoma of the stomach, has an inverse relationship to response and survival for patients who receive fluorouracil (5FU)-based chemotherapy.

PATIENTS AND METHODS

Before systemic chemotherapy, the genetic expression of TS (TSmRNA level) was determined using a PCR method. Gene expression was calculated by determining the ratio between the amount of radiolabeled PCR product with the linear amplification range of the TS gene and the beta-actin gene. Chemotherapy consisted of two cycles of protracted infusion (PI) 5FU 200 mg/m2/d administered for 3 weeks with leucovorin 20 mg/m2/w. Cisplatin 100 mg/m2 was administered on day 1.

RESULTS

Sixty-five patients with primary gastric cancer had a median TS mRNA level of 4.6 x 10(-3) (range, 0.9 to 20.1 x 10(-3)). Thirty-five percent of patients had measurable responses in their primary tumors. The mean gastric cancer TSmRNA level in responding and resistant patients is statistically significant (P < .001). The median survival time was 43+ months for treated patients with TSmRNA levels less than the median and 6 months for those with TS m-RNA levels greater than the median (P = .003).

CONCLUSION

The genetic expression of TS (TSmRNA level) influences response to 5FU-based chemotherapy and survival for a cohort of patients with primary gastric cancer. Confirmation of these data could lead to therapeutic decisions based on specific molecular properties within a tumor.

Transfection of wild-type but not mutant p53 induces early monocytic differentiation in HL60 cells and increases their sensitivity to stress

HL60 cells, which lack the p53 gene due to a deletion, were used as an in vitro model system to study the effect of wild-type p53 gene expression on hematopoietic differentiation. We transfected HL60 cells with wild-type p53 and two mutant p53 cDNAs encoding the Val to Ala mutation at codon 143 and the Arg to Trp mutation at codon 248. Flow cytometry, growth, and cytochemical analysis for alpha-napthyl butyrate esterase activity and nitroblue tetrazolium reduction indicated that wild-type p53 but not mutant p53 induced early monocytic differentiation in the transfected HL60 cells without terminal growth arrest. The wild-type p53 transfectants did not differentiate along the granulocytic pathway, even when induced with 1.25% DMSO for 6 days; rather, these cells resembled monocytic cells, confirming that wild-type p53 transfection caused these cells to become committed to differentiate along the monocytic pathway. HL60 cells transfected with wild-type p53 were more sensitive to stress, such as growth in serum-depleted medium and exposure to a chemotherapeutic agent, etoposide.

Identification of mutations by RNA conformational polymorphism "bar code" analysis

DNA single-strand conformational polymorphism (SSCP) analysis is widely used for detection of point mutations in clinical specimens. Performing SSCP analysis with cRNA instead of DNA has been shown to improve mutation detection frequency. RNA can exist in numerous meta-stable conformations, which appear as patterns of bands on nondenaturing electrophoresis gels. Single base mutations can cause not only mobility shifts of major bands, but also loss of some conformations and appearance of new conformations. Unique RNA SSCP patterns associated with specific base sequences in many cases allow visual identification of point mutations. However, in some cases, the RNA SSCP pattern of a single base change in a sequence is not sufficiently different for a positive identification of the mutation. Improvement in the detection capability of RNA SSCP was obtained by adding 3'-deoxynucleotides to the transcription reaction. The presence of chain-terminating nucleotides in the transcription reaction formed numerous new RNA fragments, thereby generating complex band patterns ("bar codes") unique to each RNA sequence. This method was applied to analyzing p53 mutations in patients with colon cancer.

Effects of cerebral TRH on intestinal water transport: role of vagal, muscarinic, and VIP pathways

Thyrotropin-releasing hormone (TRH) is a central nervous system (CNS) transmitter that stimulates various gastrointestinal secretory and motor processes by increasing vagal outflow. In this study, the CNS effects of TRH on ileal and jejunal water transport were examined in awake rats and dogs, respectively. Cerebral but not intravenous TRH (0.1-5.0 nmol/kg) significantly (P < 0.01) reversed net water absorption from approximately 30 microliters.cm-1.h-1 in rats and 300 microliters.cm-1.h-1 in dogs toward net water secretion of 60 and 600 microliters.cm-1.h-1, respectively. Truncal vagotomy and ganglionic blockade with chlorisondamine completely abolished this stimulatory effect of cerebral TRH, whereas adrenalectomy, hypophysectomy, noradrenergic and opiate blockade, and inhibition of prostaglandin and nitric oxide synthesis did not. Atropine methylnitrate significantly (P < 0.05) attenuated the stimulatory response produced by TRH by approximately 30%. Intravenous infusion of the vasoactive intestinal peptide (VIP) receptor antagonist, [4Cl-D-Phe6, Leu17]VIP (0.05-5.0 mumol.kg-1.h-1), significantly (P < 0.01) inhibited the stimulatory response of TRH by approximately 60%. Pretreatment of the animals with both atropine and the VIP antagonist completely abolished ileal and jejunal water secretion stimulated by cerebral TRH. These results indicate that 1) TRH acts within the CNS to stimulate net ileal and jejunal water secretion in rats and dogs, respectively; 2) these actions are mediated by vagal pathways; and 3) stimulation of intestinal secretion by cerebral TRH is primarily mediated by a VIP-sensitive mechanism and, in part, by a muscarinic mechanism.

Quantitation of intratumoral thymidylate synthase expression predicts for resistance to protracted infusion of 5-fluorouracil and weekly leucovorin in disseminated colorectal cancers: preliminary report from an ongoing trial

A clinical trial for patients with measurable, disseminated colorectal cancer is being conducted to determine: (1) if intratumoral expression of thymidylate synthase (TS) affects response to protracted-infusion 5-fluorouracil (5FU); and (2) whether intratumoral expression of TS increases when clinical resistance is found after response to 5-FU. Polymerase chain reaction technology is employed to determine TS expression. Using beta-actin as an internal standard, TS expressions for 26 patients range from 0.5 x 10(-3) to 22.6 x 10(-3). Currently, 22 patients are evaluable for response and TS quantitation of their measurable tumour. 8 patients (36%) have had partial responses; 3 responding patients had been previously treated with 5-FU. A strong statistical association between TS expression and resistance to therapy has been found (P = 0.004). No patient with TS expression of 4.0 x 10(-3) or greater has responded. On average, patients previously treated with 5-FU have slightly higher levels of TS expression in their measurable tumours (P = 0.4). Whether responding patients will develop increased expressions of TS upon clinical progression of their cancer remains to be determined. Confirmation of these results in a larger cohort could lead to a scientific rationale for deciding upon specific therapy for patients with disseminated colorectal cancers.