Background: Tumor budding and a proficient mismatch repair (pMMR) status are considered adverse prognostic factors in colorectal cancer (CRC). The aim of this pilot study was to assess tumor budding in primary CRC with pMMR versus that with deficient mismatch repair (dMMR). Materials and Methods: Tumor budding was retrospectively examined in the tumor from 134 patients with stage II and stage III CRC with known MMR status. The 29 available dMMR cases who developed recurrence or distant metastases (met+) were matched with a dMMR group with no recurrence or metastases (met-), and the pMMR/met+ group with pMMR/met- cases. Results: Using tumor budding cut-offs of 5 and 10, a significantly higher percentage of high-grade tumor budding (>= 5 and >= 10) was only found in the dMMR/met+ compared to pMMR/met+ subgroup (p=0.01 and p=0.02, respectively). Conclusion: A significantly higher grade of tumor budding was observed in the dMMR/met+ group, suggesting that tumor budding can provide prognostic information for patients with a dMMR status.

Background HER3 is a member of the human epidermal growth factor receptor complex (EGFR, HER2, HER3 and HER4). It has been investigated as a prognostic biomarker in colorectal cancer but is sparingly studied in colon cancer. HER3 can affect cellular proliferation, differentiation and migration in oncogenesis through ligand binding and activation of intracellular signal pathways. Recently, we found that expression of cell surface HER3 can be detected at a high extent in primary colorectal tumors, lymph node and liver metastases and that it correlated with poor prognosis. This large, explorative, retrospective study evaluates the prognostic value of HER3 in colon cancer and the association of HER3 to tumor location. Material and methods. Immunohistochemical detection with a monoclonal HER3 antibody in primary colon tumors of stage II and III, from 521 patients, was performed. Results HER3 was expressed at high levels in 67% of the colon tumors. High HER3 expression was associated with distal tumor location (p<0.0001) and low-grade tumor (p<0.0001). In the group of patients with distal colon cancer (230/521), HER3 expression correlated to shorter disease-free survival (DFS) (p=0.03) in the univariate analysis and in the multivariate analysis, a hazard ratio of 0.56 (95% CI 0.31-0.99) (p=0.047) was observed. Conclusion In this explorative, retrospective study, high HER3 expression in colon cancer was associated to distal colon location and low-grade tumor. High HER3 expression was of prognostic value according to DFS in distal colon cancer in univariate and multivariate analysis. We could not find a significant value of HER3 expression with respect to overall survival (OS).

BACKGROUND:The human epidermal growth factor receptor complex (EGFR-1, HER2, HER3 and HER4) plays an important role in pathogenesis of solid tumours. We have previously reported high expression of HER3 in 70% of primary colorectal cancer (CRC) and that high expression were linked to a worse clinical outcome. The purpose of this study is to evaluate the HER3 expression in primary CRC and metastases.MATERIAL AND METHODS:Tissue samples from primary CRC, corresponding lymph node metastases and liver metastases from 107 patients were analysed by immunohistochemistry.RESULTS:Of 107 patients, 80% showed high HER3 expression in primary CRC tumours and 81% of the stage III patients presented high expression in the lymph node metastases. All patients had liver metastases and 82% presented high HER3 expression. HER3 expression in primary tumour correlated with expression in the corresponding lymph node metastases (r = 0.65, p < 0.001) and in the liver metastases (r = 0.45, p < 0.001). A correlation between HER3 expression in corresponding lymph node and liver metastases (r = 0.65, p < 0.001) was seen.CONCLUSION:High HER3 expression is seen in about 80% of primary CRC, corresponding lymph node metastases and liver metastases. There is a correlation between HER3 expression in primary tumour and metastases in CRC.

INTRODUCTION:Metastatic disease is a major cause of death in patients with colorectal cancer (CRC). We have previously investigated expression of an orphan cytochrome P450 (CYP) enzyme, CYP2W1, and found high expression in about one third of colorectal tumors. CYP2W1 has proven to metabolize duocarmycin analogs into cytotoxic substances, compounds that in xenografts of CRC cells expressing CYP2W1 completely inhibit tumor growth. This study was designed to evaluate whether the enzyme is expressed in primary CRC and corresponding metastases.MATERIAL AND METHODS:Samples from primary tumors, corresponding lymph node metastases and liver metastases from 96 patients were collected and analyzed by immunohistochemistry. Data regarding patient's demographics, tumor characteristics and survival were also collected.RESULTS:Out of 96 patients, 25 (26%) had high CYP2W1 expression in the primary tumor and 46 (48%) showed high levels in the liver metastasis. In total 59 patients had lymph node metastases, and 31% of them had high CYP2W1 expression. When comparing the expression in primary tumor with that of the first liver metastasis, the increase in expression was statistically significant (p = 0.005).CONCLUSION:High CYP2W1 expression is seen in 26% of primary CRC and in 48% of corresponding liver metastases. This opens possibilities for new targeted therapies to metastatic CRC in the future.

The establishment and maintenance of apical-basal cell polarity is essential for the functionality of glandular epithelia. Cell polarity is often lost in advanced tumours correlating with acquisition of invasive and malignant properties. Despite extensive knowledge regarding the formation and maintenance of polarity, the mechanisms that deregulate polarity in metastasizing cells remain to be fully characterized. Here we show that AmotL2 expression correlates with loss of tissue architecture in tumours from human breast and colon cancer patients. We further show that hypoxic stress results in activation of c-Fos-dependent expression of AmotL2 leading to loss of polarity. c-Fos/hypoxia-induced p60 AmotL2 interacts with the Crb3 and Par3 polarity complexes retaining them in large vesicles and preventing them from reaching the apical membrane. The resulting loss of polarity potentiates the response to invasive cues in vitro and in vivo in mice. These data provide a molecular mechanism how hypoxic stress deregulates cell polarity during tumour progression.

Introduction: Tumor budding is considered an adverse prognostic factor in colorectal cancer (CRC). A poorer prognosis is also observed in CRC patients with a proficient mismatch repair (pMMR) status. The aim of this study was to assess tumor budding in pMMR versus deficient mismatch repair (dMMR) in CRC. Methods: Tumor budding was retrospectively examined using immunohistochemistry with pan-cytokeratin MNF-116 staining in the primary tumor from 134 patients with stage II and stage III CRC with known MMR status. The patients were included in an adjuvant Nordic trial between 1991 and 1996 randomly assigned to either surgery or surgery plus adjuvant 5-Fluorouracil (5-FU)-based chemotherapy. A total of 29 patients with tumors classified as dMMR status that had developed recurrence or distant metastases (dMMR/Met+) were matched according to age, gender, stage and treatment to 33 patients with dMMR status that had no recurrence or metastases (dMMR/Met-), 42 patients with pMMR status and no recurrence or metastases (pMMR/Met-) and 30 patients with pMMR and recurrence or distant metastases (pMMR/Met+). Assessment of tumor budding with MNF-116 staining was done by two independent investigators (MK, CL) counting at x20 magnification the number of tumor buds at the invasive tumor margin. Using quartile cut-offs the degree of budding was categorized into low-grade and high-grade tumor budding. Results: In the entire study population we found median budding to be 5 and the range 0-35 (SD ± 6). There was substantial agreement between the two investigators (MK and CL) on the presence of tumor budding p < 0.001, r = 1.0. In the lower quartile cut-off of 3 a tendency to high-grade tumor budding (≥3) was seen in the pMMR groups (Met+ and Met-) compared to the dMMR groups (Met+ and Met -) (p = 0.09) and in the subgroup pMMR/Met- compared to dMMR/Met- (p = 0.09). Using the median cut-off of 5 and upper quartile cut-off of 10 a higher percentage of high-grade tumor budding (≥5 and ≥10) was only found in the subgroup dMMR/Met+ compared to pMMR/Met+ (72% vs 40%, p = 0.01 and 45% vs 17%, p = 0.02, respectively). Regardless of cut-off used no survival advantage was observed in the entire cohort for the low-grade tumor budding group compared to the high-grade group. Conclusion: In this study a significant higher number and grade of tumor budding was observed in the dMMR/Met+ group. This suggests that tumor budding could provide more accurate prognostic information for patients with a dMMR status and aid in the clinical decision of adjuvant chemotherapy especially in Stage II CRC patients.

Aim To evaluate the expression and prognostic value of the epidermal growth factor receptor HER3 in patients with primary colorectal cancer (CRC) and corresponding lymph node metastases. Patient and methods HER3 expression was analysed immunohistochemically (IHC) in primary tumours and in corresponding lymph node metastases from 236 patients with stage II and III CRC. In 58 primary tumours, fluorescence in situ hybridisation (FISH) detection was performed. Results HER3 was detected at high frequency in the cell membrane. Seventy percent of the primary tumours had a high HER3 expression compared to 75% in the lymph node metastases. HER3 expression in the primary tumour was an independent prognostic factor for overall survival in the entire group of patients (p = 0.026) and in the subgroup of patients with colon cancer stage II (p = 0.030). A high HER3 expression in the primary tumour was associated with worse clinical outcome. The expression of HER3 was homogenous within the primary tumour (r = 0.9, p < 0.0001) and correlated with the HER3 expression in corresponding lymph node metastases (r = 0.6, p < 0.0001). No gene amplification with respect to HER3 was seen in primary tumours using FISH analysis. Conclusion A high HER3 expression was found in 70% of the primary CRC tumours and in 75% of the corresponding lymph node metastases. HER3 expression in the tumour was an independent prognostic factor, where a high HER3 expression was associated with worse clinical outcome. There was a correlation in HER3 expression between primary tumour and corresponding lymph node metastases.

This study in 716 colon cancer patients evaluates if a combined instead of a single marker analysis of mismatch repair (MMR) status and thymidylate synthase (TS) expression could individualize the treatment decision. The results indicate that a combined analysis of MMR status and TS expression can improve prediction of response to adjuvant 5-fluorouracil (5-FU)-based chemotherapy in stage Ill colon cancer.Background: Colon cancer with mismatch repair deficiency and low TS expression has been associated with an improved prognosis. Data also indicate that MMR proficient colon cancer with high TS expression has a better response to adjuvant 5-FU-based chemotherapy. This study evaluates if a combined analysis of MMR status and TS expression in colon cancer can add prognostic value and better predict response to adjuvant 5-FU-based chemotherapy. The potential relationship between MMR status and TS expression is also investigated. Patients and Methods: This study includes a subgroup of 716 patients with colon cancer out of 2,224 stage II and stage III colorectal cancer patients enrolled in Nordic trials randomized to surgery alone or surgery plus adjuvant 5-FU-based chemotherapy. After immunohistochemical analysis of tumor MMR status and TS expression the patients were divided into 4 groups. Results: There was a nonsignificant difference in overall survival between group 1 (patients with deficient MMR tumors with low TS) and group 4 (patients with proficient MMR tumors expressing high TS). When comparing group 1 and group 4 patients treated with surgery alone a trend to better overall survival was found in group 1, P = .06. In group 4, stage III patients had a significantly improved survival when receiving adjuvant 5-FU-based chemotherapy compared with surgery alone, P = .01. No relationship was found between MMR status and TS expression. Conclusions: A combined instead of a single marker analysis of MMR status and TS expression can improve the prediction of response to 5-FU-based chemotherapy in stage III colon cancer. (C) 2013 Elsevier Inc. All rights reserved.

Abstract Background. Mismatch repair (MMR) status has been reported as a prognostic and predictive factor in sporadic colorectal cancer (CRC). The purpose of this study was to determine the prognostic and predictive value of MMR protein expression in the adjuvant setting. Patients and methods. The MMR status in the primary tumor was retrospectively assessed on paraffin-embedded formalin-fixed samples from 1 006 patients with sporadic CRC (488 stage II and 518 stage III) using immunohistochemical analysis (IHC) of MLH1 and MSH2 expression. The patients were included in adjuvant Nordic trials between 1991 and 1996 randomly assigned to surgery alone or surgery plus adjuvant 5-fluorouracil (5-FU)-based chemotherapy. Data was censored at 120 months after surgery. Results. One hundred fifty-seven patients (15.6%) showed a loss of MMR protein expression (139 MLH1 negative, 15 MSH2 negative and 3 MLH1 and MSH2 negative) and were classified as MMR protein negative. A normal MMR protein expression was found in 849 patients who were defined as MMR protein positive. MMR protein expression was a significant prognostic marker in the entire study group with a better overall survival (OS) among patients with MMR protein negative tumors compared to patients with MMR protein positive tumors (p=0.01). In a multivariate analysis the MMR protein expression was significantly associated with OS, (HR 0.70 [95% CI, 0.40 to 0.99]; p=0.01). The MMR status did not predict survival benefit from adjuvant 5-FU-based chemotherapy. Conclusion. This study reveals that IHC of MLH1 and MSH2 expression can yield important prognostic information but is not a predictive factor for adjuvant 5-FU-based chemotherapy in sporadic CRC.

AIM:To investigate thymidylate synthase (TS) expression in primary colorectal cancer (CRC) as a prognostic and predictive marker of benefit for adjuvant chemotherapy.PATIENTS AND METHODS:TS expression was immuno0-histochemically (IHC) assessed on tumors from 1,389 patients with stage II and III CRC randomly assigned to either surgery alone or surgery plus 5-fluorouracil (5-FU)-based adjuvant chemotherapy.RESULTS:In the subgroup treated with surgery alone (n=708), TS expression was prognostic using the classification of TS 0-1 versus 2-3 (p=0.045) as well as TS classified as 0-2 versus 3 (p=0.002). A high TS expression was associated with a shorter overall survival. Among patients with TS grade 3 (n=460), the subgroup treated with adjuvant chemotherapy had a significant longer OS (p=0.005).CONCLUSION:In this study TS, immunohistochemically assessed, is a prognostic factor in CRC patients treated with surgery alone. Patients with the highest level of TS expression (grade 3) had an improved clinical outcome following adjuvant 5-FU-based chemotherapy.

BACKGROUND:In advanced colorectal cancer (CRC) a low expression of thymidylate synthase (TS) in metastases predicts a higher response to 5-fluorouracil (5-FU). The purpose of this study was to investigate the expression of TS in liver and lung metastases of CRC and their matched primary tumours.PATIENTS AND METHODS:Immunohistochemical analysis of TS expression was performed on tissue samples of 48 CRC metastases (liver n=38, lung n=10) and their matched primary tumours (n=45).RESULTS:There was no significant correlation between TS expression in 33/48 (69%), matched samples of metastases and primary tumours (r=0.02, p=1.0).CONCLUSION:This study indicates that TS expression in liver and lung metastases of CRC does not always reflect the level of TS in their corresponding primary tumours. Therefore, it might not be accurate to solely rely on analyses of TS in the primary tumours to predict the effect of 5-FU-based chemotherapy in metastatic CRC.

The prognostic significance of the number of lymph nodes examined in surgical specimen of colorectal cancer was determined. One thousand and twenty five patients with colorectal cancer stage II and III were included in the study. These patients underwent surgery from 1991 to 1997 and were enrolled in clinical trials to evaluate the efficacy of adjuvant 5-fluorouracil (5FU) based chemotherapy. The median number of examined lymph nodes was five. Only 13% of the patients had > or = 12 lymph nodes analyzed. The number of examined lymph nodes was an independent prognostic factor for overall survival in the entire group of patients with stage II and III colorectal cancer (p=0.009). Patients with a higher number of lymph nodes examined had a longer overall survival. In stage III colorectal cancer the ratio of the number of metastatic lymph nodes to the number of examined lymph nodes (lymph node ratio, LNR) was an independent prognostic factor for overall survival. A decreasing LNR was correlated with a longer overall survival (p<0.0001). Increasing age was associated with a reduction of lymph node harvest (p=0.04). Patients with rectal cancer treated with preoperative radiotherapy had a lower number of lymph nodes analyzed compared with non-radiated (p<0.001). The number of examined lymph nodes in the surgical specimen is an independent prognostic factor for overall survival in colorectal cancer. The LNR is an independent prognostic factor in stage III colorectal cancer.

4126 Background: Microsatellite instability (MSI) is the hallmark of a defective DNA mismatch repair (MMR) and occurs in 10- 20 % of sporadic colorectal cancer (CRC). The loss of the MLH1 protein is the cause of MSI in almost all sporadic colorectal MSI tumours. The second most common protein to be lost is MSH2. There is evidence that MSI is a prognostic factor in CRC. The role of MSI status as a predictive factor of benefit from adjuvant 5-fluorouracil (5-FU) based chemotherapy is controversial. Methods: Monoclonal antibodies that recognize the mismatch repair protein by immunohistochemistry (IHC) have been commercially available for several years. Previous reports have found a strong correlation between MMR results obtained by immunohistochemical and genetic analysis. This study included 1006 CRC patients (488 Stage II and 518 Stage III) with a median follow-up of 5 years. The patients were included in Nordic trials randomised between surgery alone and surgery plus adjuvant 5-FU. The MMR status was retrospectively assessed on paraffin-embedded formalin-fixed samples using IHC. Results: One hundred fifty seven patients (15.6 %) showed a loss of MMR protein expression (139 MLH1 negative, 15 MSH2 negative and 3 MLH1+MSH2 negative) and were classified as MMR protein negative. A normal MMR protein expression was found in 851 patients who were defined as MMR protein positive. The median overall survival (OS) was 84 months (range 2–181 months). MMR protein expression was a significant prognostic marker in the entire study group where a better OS was seen among patients with MMR protein negative carcinomas compared to patients with MMR protein positive tumours (p=0.005). In multivariate analysis the MMR protein expression was significantly associated with OS, (hazard ratio for death, 0.67 [95 per cent confidence interval, 0.38 to 0.96]; p=0.008). However, in this study the MMR status did not predict response to 5-FU adjuvant chemotherapy. Conclusions: This study reveals that immunohistochemical analysis of MLH1 and MSH2 expression can yield important prognostic information but is not a predictive factor in sporadic CRC. No significant financial relationships to disclose.

PURPOSE:The level of thymidylate synthase (TS) in primary colorectal cancer (CRC) has been reported as a prognostic marker. The purpose of this study was to determine whether TS expression in lymph node metastases of Dukes' C CRC is a prognostic marker.PATIENTS AND METHODS:TS expression in the primary tumor and lymph node metastases from 348 patients with Dukes' C CRC was retrospectively assessed using immunohistochemistry and the monoclonal antibody TS 106. The patients had all been enrolled onto our previous study of 862 CRC patients who were included in Nordic trials that randomly assigned the patients to either surgery alone or surgery plus adjuvant chemotherapy.RESULTS:TS expression in lymph node metastases was a distinct prognostic marker in the entire study group for overall survival (OS; P = .02) and disease-free survival (DFS; P = .04). A low TS expression in the lymph node metastases correlated with a better clinical outcome. In the subgroup of patients treated with surgery alone, the expression of TS in lymph node metastases also had a prognostic value for OS (P = .04) and DFS (P = .03), but this was not the case for the other subgroup who received adjuvant fluorouracil-based chemotherapy (OS, P = .5; DFS, P = .2). The expression of TS in the primary tumor only had a significant prognostic value among patients who were treated with surgery alone (OS, P = .03; DFS, P = .03) and not among the entire patient population.CONCLUSION:These data show that TS expression in lymph node metastases is a prognostic marker for patients with Dukes' C CRC.

BACKGROUND:Levels of the enzyme thymidylate synthase (TS) are of prognostic significance in colorectal cancer. It may be argued that the levels of TS merely reflect the proliferative activity and could be replaced by markers of proliferation.MATERIALS AND METHODS:We used immunohistochemical approaches to examine the expression of TS, Cyclin A and Ki-67 in morphologically well-defined tumor areas in consecutive slices of rectal cancer, using the antibodies TS 106, NCL-Cyclin A and Mib-1.RESULTS:There was a linear relationship between Cyclin A- and Ki-67-positive cells (p < 0.0001). There did not seem to be any significant relationship between TS-expression and the frequency of Cyclin A-positive cells (p = 0.1) but a significant correlation was observed between TS-expression and the frequency of Ki-67-positive cells (p = 0.02).CONCLUSION:TS, immunohistochemically-detected in rectal cancer cells, is not associated with an accurate assessment of the proliferative stage. The prognostic value of TS determination can only partly be explained by the proliferative activity.

PURPOSE:We studied the prognostic value of thymidylate synthase (TS) expression in primary colorectal cancer (CRC) and the role of TS expression as a predictor of chemotherapeutic benefit in patients treated with adjuvant chemotherapy.PATIENTS AND METHODS:TS expression was immunohistochemically assessed on tumor sections from 862 patients with CRC Dukes' stages B and C enrolled onto randomized trials evaluating fluorouracil (5-FU)-based adjuvant chemotherapy.RESULTS:TS expression was an independent prognostic factor for disease-free (P =.05) and overall survival (P =.05). In the subgroup treated with surgery alone, TS was an independent prognostic factor for disease-free (P <.001) and overall survival (P =.001), whereas this was not the case in the subgroup of adjuvantly treated patients. Patients whose tumors expressed high TS levels had a tendency to improved outcome after adjuvant therapy (not significant). The group whose tumors expressed the highest TS grade, grade 3 (34% of the patients), had a significantly longer disease-free survival if they were treated with adjuvant therapy compared with surgery alone (multivariate analyses, P =.02), whereas patients whose tumors expressed low TS levels (28% of the patients) had an impaired outcome after adjuvant therapy (multivariate analyses: disease-free survival, P =.01; overall survival, P =.01).CONCLUSION:TS expression predicts for survival independent of Dukes' stage in patients with CRC treated with surgery alone. The study indicates that patients with high TS levels may benefit from adjuvant 5-FU-based chemotherapy. However, patients with low TS levels seem to have a worse outcome when treated with adjuvant chemotherapy.

Several studies have suggested that the intratumoral level of thymidylate synthase (TS) in colorectal tumors correlates with survival. We have studied the correlation between TS expression in primary rectal cancer and locoregional recurrence, distant metastases, and survival. TS enzyme levels were evaluated immunohistochemically using the specific monoclonal antibody TS 106 in paraffin-embedded tumors from 243 patients who had undergone primary surgery for rectal cancer during the years 1980-1993. All patients were included in prospective randomized trials aimed at determining the clinical value of a short preoperative course of local radiation therapy (five doses of 5 Gy each). With a median follow-up of 94 months (range, 43-202 months), it was observed by multivariate analysis that Dukes' stage and TS expression were independent prognostic markers of locoregional recurrence (P < 0.001 and P = 0.038, respectively) distant metastasis (P < 0.001 and P = 0.011, respectively) disease-free survival (P < 0.001 and 0.014, respectively), and overall survival (P < 0.001 and 0.020, respectively). By multivariate analysis, preoperative irradiation therapy showed a borderline improvement in locoregional recurrence (P = 0.051). No other factors, such as age, sex, differentiation of the tumor, or p53 expression, were noted to be independent prognostic factors for clinical outcome in these patients. We concluded that the intratumoral expression of TS in primary rectal cancer is an independent prognostic factor for locoregional recurrence, distant metastases, disease-free survival, and overall survival. Patients with low intratumoral TS expression had a significantly better outcome than those with high TS expression.

Folinic acid (leucovorin) is frequently used to augment and modulate the clinical activity of 5-fluorouracil (5-FU) in patients with advanced gastrointestinal (Gl) cancer. However, there are conflicting opinions concerning the optimal doses for these patients, and whether folinic acid modulates the clinical activity of 5-FU in patients with non-Gl cancer. To elucidate these questions, model experiments have been performed on human tumor cell lines in vitro to determine the modulatory activity of various concentrations of folinic acid on 5-FU mediated cytotoxicity using a clonogenic assay. Three cell lines of colon cancer and 3 of glioblastoma origin were exposed to 5-FU alone or with folinic acid for 24 hours. It was observed that relatively low concentrations of folinic acid enhanced the cytotoxicity of 5-FU against the colon cancer lines whereas higher concentrations were less effective. Folinic acid did not enhance the 5-FU mediated killing of the glioma cell lines at any concentration (0.01-100 micrograms/ml). On the contrary, folinic acid seemed to counteract the cytotoxic effect of 5-FU in a reasonably dose-dependent fashion. These results may suggest that the value of folinic acid in the treatment of non-Gl cancer with 5-FU should be evaluated within the framework of controlled clinical trials, and that high doses of folinic acid may not necessarily be more effective than low.

Unlike "conventional" oxazaphosphorines such as cyclophosphamide (CP) and ifosfamide, a relatively new drug termed 4-hydroperoxy-CP (4-HC) degrades spontaneously in water yielding phosphoramide mustard considered to be the activated cytotoxic metabolite. During this degradation a toxic, volatile factor termed acrolein is also formed. In order to examine the possible role of this compound in 4-HC-induced inhibition of tumor cell growth in vitro, 8 different established human tumor cell lines were cultured in the presence of 4-HC or equimolar concentrations of acrolein. It was observed that the cell lines differed widely with respect to sensitivity to these compounds. However, each individual cell line exhibited virtually identical sensitivities to both 4-HC and acrolein. The observation that 2-mercaptoethansulfonate (mesna), which is highly reactive with acrolein but not with phosphoramide mustard, could markedly reduce the cytotoxic activity of 4-HC indicates that acrolein may play an important role in 4-HC induced cell damage in vitro.

2-Mercaptoethanesulfonate (mesna) is a nontoxic drug which upon intravenous and oral administration effectively prevents urothelial toxicity in cancer patients treated with oxazaphosphorines. Mesna is rapidly oxidized to dimesna in the blood. It is then taken up by kidney tubular cells in which it is reduced and excreted into the urine as mesna where it reacts with toxic metabolites. We have observed that mesna, but not dimesna, may inhibit growth of several human malignant cell lines in vitro. Some are extremely sensitive, whereas others are more or less resistant. It was found that 2/4 relatively resistant human bladder cancer cell lines turned sensitive upon repeated administrations of mesna and 5/5 cell lines appeared to be sensitive to mesna when grown in serum-free medium. The results seem to provide an explanation of the remarkable positive clinical effects of prolonged oral mesna treatment in patients with superficial bladder cancer.