[hutchibk]

I believe that studies are showing that it simply ISN'T true that glutamine potentially could promote tumor growth...

Here's what I found: (from March 2007)

http://theoncologist.alphamedpress.o.../full/12/3/312


Excerpts:

"...Glutamine is a gluconeogenic nonessential amino acid that isstored primarily in skeletal muscle and liver [14], and is oftendepleted in stress states, such as malignancy [16]. It servesas the primary carrier of nitrogen and is the main energy sourcefor rapidly proliferating cells. Rapid proliferation of a tumormay deplete glutamine stores and subsequently lead to cancer-relatedcachexia [17]. Studies have indicated that glutamine supplementationis well tolerated and potentially effective in preventing sideeffects for patients receiving high-dose chemotherapy and bonemarrow transplantation [25]. Supplementation with glutaminecan also protect against doxorubicin-induced cardiac toxicity[26] and prevents atrophy of the intestinal mucosa in patientsreceiving total parenteral nutrition [27]. Preliminary animalstudies suggest that glutamine may prevent neurotoxicity causedby vincristine, cisplatin, as well as paclitaxel [28, 29]. Clinically,paclitaxel-induced myalgias and arthralgias have been successfullyreduced by glutamine in breast cancer patients [30]. Glutaminesupplements may also reduce the severity of peripheral neuropathyin metastatic breast cancer patients receiving high-dose paclitaxeland hematopoietic stem cell transplantation [18]. Interestingly,a byproduct of glutamine metabolism has been identified thatprotects advanced CRC patients from oxaliplatin-induced neuropathy[13].

In the current study, supplementation with glutamine significantlyreduced the incidence and severity of peripheral neuropathyas well as the need for dose reduction of oxaliplatin in thesepatients (Tables 1 and 3). These properties may increase thetherapeutic index of oxaliplatin. The potential role of glutamineas a neuroprotectant may be better understood in the contextof the current hypothesis explaining chemotherapy-induced neuropathy.A study of circulating nerve growth factor (NGF) levels in cancerpatients treated with neurotoxic chemotherapeutic agents foundthat peripheral neuropathy worsened as serum levels of NGF declined[31]. Moreover, the administration of NGF prevents paclitaxel-inducedneuropathy in mice [32]. Because glutamine is known to upregulateNGF mRNA in an animal model [33], glutamine supplements mayprevent chemotherapy-induced neuropathy via upregulating theNGF level. On the other hand, it has also been hypothesizedthat high systemic levels of glutamine may downregulate theconversion of glutamine to an excitatory neuropeptide, glutamate,which may also account for the reduced symptoms observed inpatients receiving glutamine [34]...."
<sup>

</sup>"...A major concern is that glutamine supplements might protecttumor cells from the cytotoxic effects of chemotherapy. However,in the current study, no between-group difference was foundin the response to chemotherapy (52.4% versus 47.8%; p = .90)or survival (p = .79; log-rank test). Although in vitro evidenceof the dependence of tumor growth on glutamine has deterredits application in cancer patients [36], several studies havefailed to show that supplemental glutamine stimulates tumorgrowth [37, 38]. In fact, accumulating in vivo evidence suggeststhat glutamine may actually decrease tumor growth, possiblyby upregulating the immune system [37, 39]. The net outcomemay improve the therapeutic index of oxaliplatin. The overalllymphocyte response (i.e., entry into the cell cycle and proliferation)has been directly correlated with glutamine concentration ofthe culture medium [40]. In a breast cancer xenograft model,the supplemental glutamine group had higher natural killer cellactivity and nearly one half the tumor volume, compared withthe placebo group [41]..."