Can successful cancer therapies build on what we learn from complex disorders?

In vitro quantification: Long-term effect of glucose deprivation on various cancer cell lines

OBJECTIVE

Although metabolic treatment of highly glycolytic cancers and metastases is becoming an important research field, the effects of such treatments are not fully quantified yet. In this article we attempt to quantify the effect of long-term glucose deprivation (similar to ketogenic diets) on cancer cells using in vitro tests.

METHODS

Two tumorigenic cell lines were used, namely a metastatic breast and a cervical cancer cell line. The non-tumorigenic control cell line was an immortalized breast cell line. All the cell lines were stabilized at a typical average human blood glucose level of 6 mmol/L. The cell lines were then exposed to the therapeutic blood glucose level of 3 mmol/L for 90 d.

RESULTS

The tests indicated that glucose deprivation restricted the different cancer cell lines' growth more than that of non-tumorigenic cells. The different cell lines were also differentially affected, which suggests that long-term glucose deprivation will not be equally effective for different types of cancer. The highly glycolytic breast cancer cell line was most adversely affected, with cell growth decreasing to 30% after 26 d. Cell growth was stable at this level for up to 22 d. Furthermore, all of the other cancer cell lines were similarly affected.

CONCLUSIONS

This in vitro data could help to direct future human in vivo tests to find the most therapeutic time (cancer cells at their most vulnerable) for additional short-term adjuvant therapies. Partial recovery of proliferation occurred after 90 d. Therefore, as expected, the results also indicated that without an adjuvant treatment, full extinction cannot be reached with the proposed long-term metabolic treatment. The need for more clinical data on long-term glucose deprivation treatments for cancer is well described in the literature. This paper attempts to add to the available pool of knowledge.

Tumor cell culture survival following glucose and glutamine deprivation at typical physiological concentrations

OBJECTIVE

Most glucose (and glutamine)-deprivation studies of cancer cell cultures focus on total depletion, and are conducted over at least 24 h. It is difficult to extrapolate findings from such experiments to practical anti-glycolytic treatments, such as with insulin-inhibiting diets (with 10%-50% carbohydrate dietary restriction) or with isolated limb perfusion therapy (which usually lasts about 90 min). The aim of this study was to obtain experimental data on the effect of partial deprivation of d-glucose and l-glutamine (to typical physiological concentrations) during 0 to 6-h exposures of HeLa cells.

METHODS

HeLa cells were treated for 0 to 6 h with 6 mM d-glucose and 1 mM l-glutamine (normal in vivo conditions), 3 mM d-glucose and 0.5 mM l-glutamine (severe hypoglycemic conditions), and 0 mM d-glucose and 0 mM l-glutamine ("starvation"). Polarization-optical differential interference contrast and phase-contrast light microscopy were employed to investigate morphologic changes.

RESULTS

Reduction of glucose levels from 6 to 3 mM (and glutamine levels from 1 to 0.5 mM) brings about cancer cell survival of 73% after 2-h exposure and 63% after 4-h exposure. Reducing glucose levels from 6 to 0 mM (and glutamine levels from 1 to 0 mM) for 4 h resulted in 53% cell survival.

CONCLUSION

These data reveal that glucose (and glutamine) deprivation to typical physiological concentrations result in significant cancer cell killing after as little as 2 h. This supports the possibility of combining anti-glycolytic treatment, such as a carbohydrate-restricted diet, with chemotherapeutics for enhanced cancer cell killing.