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Page 6 of 38 J Cancer Metastasis Treat 2020;6:5 I http://dx.doi.org/10.20517/2394-4722.2020.13

Background: The glucose deprivation Restricted Ketogenic diet (KD-R) in combination with Metformin
use, is a non-toxic broad-spectrum approach that targets the important metabolic differences between
normal and cancer cells. The optimal use of this approach for cancer treatment is investigated using in vitro
tests.

Method: Tests were carried out at 3-mmol/L blood glucose (BG) to mimic the BG effect of KD-R in
combination with Metformin. Two breast and one cervical cancer as well as one non-tumorigenic cell were
used.

Results: The different cell lines were affected differently. This suggests that glucose deprivation via KD-R
and Metformin will not equally affect different cancers. All cell lines were most adversely affected after
three weeks. Cell growth decreased to 32% for the most glucose avid cancer cell line.

Partial recovery occurred after three months. Full cancer extinction can thus not be reached with only
KD-R and Metformin. Adjuvant treatments are needed. These treatments should be done when the cancer
cells are at their most vulnerable, i.e., three weeks after reaching a BG level of 3 mmol/L.

Future work: Future work will entail adjuvant treatments such as chemotherapy together with KD-R and
Metformin. Results should be available before the conference. The focus of our conference presentation is
on the latest results.

8. DNA repair and damage response in personalized brain cancer chemotherapy

Bernd Kaina, Yang He, Oliver Switzeny, Wynand P. Roos, Markus Christmann, Thomas Hofmann

Institute of Toxicology, University Medical Center Mainz, Mainz D-55130, Germany.

Background and aim: The first-line chemotherapeutic for malignant glioma is the DNA methylating agent
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temozolomide. The mechanism of cell death triggered by the minor DNA lesion, O -methylguanine,
induced by the agent is well described. It rests on conversion of the lesion through mismatch repair into
[1]
DNA double-strand breaks (DSB) that trigger downstream pathways including apoptosis and senescence .
Consequently, corresponding repair pathways are expected to have a great impact on temozolomide
6
resistance, and evidence was provided for the involvement of O -methylguanine DNA methyltransferase
(MGMT), mismatch repair, and DSB repair by homologous recombination through BRCA2 and Rad51 as
[2]
[3]
well as XRCC3 . However, only MGMT found the way into the clinic, being used as predictor for therapy
outcome .
[4]
Experimental procedure: A battery of cell und molecular biological methods was applied, including
apoptosis, senescence, and autophagy measurements.

Results: We compared methods of determining the MGMT promoter methylation status, which corresponds
to MGMT silencing and therapy, and showed that MS-HRM is superior compared to methylation-specific
[5]
6
polymerase chain reaction . We also show that downstream of O -methylguanine derived DSBs are ATR/
ATM triggered pathways that activate apoptosis and senescence. Thus, data are shown demonstrating that
[6]
the SIAH1-HIPK2-p53ser46 pathway plays a key role in regulating temozolomide-induced apoptosis . The
[7]
question of temozolomide threshold doses in activating survival and death pathways is also addressed .
Conclusion: MGMT, mismatch repair and the SIAH1-HIPK2-p53ser46 pathway are key elements in
personalized glioblastoma therapy with DNA-alkylating drugs.