Introduction

5-fluorouracil (5-FU), is an antimetabolite, anticancer agent which is used as an essential part for the treatment of wide range of solid tumors. It has antitumor activity against epithelial malignancies arising in the gastrointestinal tract , breast as well as the head and neck(Malet-Martino and Martino, 2002 ).As all the anticancer agents, 5-FU leads to several toxicities. Myelotoxicity is the major toxic effect in patients receiving bolus doses (Takimoto and Page, 2004).

The haemopoietic growth factor ( granulocyte-colony stimulating factor G-CSF) was proved to shorten the duration and decrease the severity of chemotherapy induced neutropenia (Liang, 2003).

Lamson and Brignall, (2000)demonstrated the cytoprotective effect of glutathione (GSH) against chemotherapeutic agents. Kojima et al.(2003)suggested that glutathione could prevent the 5-FU-induced haemopoietic toxicities and accelerate recovery from such toxicities.

The aim of the present study was to evaluate the effect of combining both GSH and G-CSF on their chemoprotective functions.

Material and Methods

Drugs

Animals

Samples collection

Statistical analysis

Results

Haematological parameters and bone marrow cytology: Table (1)

As regards TLC and bone marrow cytology it was found that groups 3 ( received G-CSF ), and 6 (received G-CSF before 5-FU and killed 1 day later) have higher (i.e. better) values than the control, while other groups have lower values ( i.e. worse ). TLC was higher also in group 5 (received GSH before 5-FU and killed 1 day later) than the control. The peripheral leukopenia and medullary myelosuppression in this study are detected in mice received 5-FU either alone or with pretreatment of combined GSH and G-CSF. (Table 2)

When comparing TLC and bone marrow cytology, groups 5 (GSH +5-FU) and 6 (G-CSF + 5-FU) were significantly higher than group 4 (5-FU only). Also both groups were significantly higher than group 7 (GSH+G-CSF+ 5-FU).

Group 7 showed no significant difference with group 4 regarding TLC and bone marrow cytology, but showed significantly lower counts than groups 5 and 6 (Table 3).

Figure 1

Table 1: Haematological parameters and bone marrow cytology in all studied groups.

Figure 2

Table 2: Comparison of haematological parameters and bone marrow cytology in all studied groups versus control group.

Figure 3

Table 3: Comparison of haematological parameters and bone marrow cytology in mice killed 1 day after receiving: 5-FU (gp 4), 5-FU preceeded by GSH pretreatment (gp 5), 5-FU preceeded by G-CSF pretreatment (GP 6) and 5-FU preceeded by combined GSH and G-CSF pretreatment (gp 7).

Discussion

5-fluorouracil has been used for the treatment of cancer for more than 40 years and is the most commonly prescribed chemotherapeutic agent (Dobritzsch et al.,2001). Chemotherapy-induced neutropenia, the primary dose-limiting toxicity of most cancer chemotherapy agents, is associated with numerous negative consequences, including life-threatening infections (Dale, 2003).

Glutathione is a naturally occurring endogenous antioxidant that is cytoprotective. Thus, treatment with glutathione or its precursors may protect normal cells during cancer chemotherapy(Doolittle et al.,2002 )and that is what happened in our study.

Priming has been defined as the administration of a colony stimulating factor prior to chemotherapy. There are several theoretical reasons why this schedule of administration may prove to be advantageous (Lowenberg et al., 2003).Again this was proven in this work.

However, the combined pretreatment with GSH and G-CSF reveal no protection at all denoted by presence of leucopenia in tested group.

These results could be explained by the work ofSattler et al. (1999). They found that haematopoietic growth factors signals through the formation of reactive oxygen species (ROS) and that antioxidants e.g. N-acetyl cysteine (a glutathione precursor) reduced growth and viability of cells.

AlsoGate et al. (2004) have shown that G-CSF was more effective at stimulating proliferation of haematopoietic cells in glutathione transferase (GST) deficient mice than in wild type. This is explained by the fact that GST interacts with and suppresses c-Jun NH2-terminal kinase [an enzyme which is responsible for increased myeloproliferation].

Despite the previous works it may be the first time to test these results in vivo instead of cellular level.

Cascinu et al. (1997), however contradict these findings and this could be explained by the fact that there was a separation between G-CSF and GSH as regards days of administration which could prevent the antagonism between them.

It can be concluded from this work that the chemoprotective effect of GSH and G-CSF is diminished if they are combined during treatment. So, some times one plus one does not equal two but instead a big zero.