ESTRO 36 Abstract Book

S201

ESTRO 36

_______________________________________________________________________________________________

Results

In SCC compared to AC, lesion MR

glc

and k

were

significantly higher and V

was significantly lower. AC

showed less heterogeneity relative to SCC in terms of

mean MR

glc

, k

and V

. In SCC, a significant higher value for

and lower value for V

was found in regions with higher

glc

Percentage ECAR under normoxic conditions was higher in

AC than SCC cell lines, corresponding to the presence of

F-FDG metabolism in areas with high V

in AC on dynamic

PET. Differences between histological subtypes were less

obvious in the inhibitor experiments. All cell lines show

decreased growth rate by glycolysis inhibition using

lonidamine. The combination of lonidamine with the

glutaminase inhibitor 968 was detrimental for cell growth.

In all cell lines, except H520, apoptotic index increased

using the combination therapy.

Conclusion

Adeno NSCLC show glycolysis under better

perfused/oxygenated conditions (aerobic glycolysis)

vivo

and

in vitro

, while SCC NSCLC exhibit anaerobic

glycolysis (high glycolytic rate under poor

vascularization). Apart from glucose, glutamine usage is

critical for these tumors. All cell lines show a marked

growth delay with increased apoptosis upon metabolic

inhibition with both lonidamine and 968. Therefore,

inhibiting metabolism might be a general approach to

optimize treatment, especially in combination with

radiotherapy in NSCLC.

PV-0373 Epigenetic and metabolic reprogramming as a

target for prostate tumor radiosensitization

A. Dubrovska

, C. Peitzsch

, A. Tyutyunnykova

, M. Cojoc

OncoRay - Center for Radiation Research in Oncology,

Medical Faculty Dresden Carl Gustav Carus- TU Dresden,

Dresden, Germany

Purpose or Objective

Radiotherapy remains one of the main modalities to treat

solid cancers and is one of the mainstays of curative

prostate cancer treatment. Nevertheless, the risk of

recurrence after radiotherapy still remains substantial in

locally advanced disease. Tumor relapse after

radiotherapy is attributed to the population of cancer

stem cells (CSCs) which survived the treatment.

Therefore, analysis of the CSC populations might be an

important predictive tool of radiotherapy outcome and

individualized treatment selection. However, compelling

evidence suggests a high plasticity of CSCs imposed by

tumor treatment. This study is aiming to investigate the

interconnection of the glutamine metabolism and cancer

cell plasticity in the development of tumor radioresistance

for the development of new biomarkers to predict

radiation treatment outcome.

Material and Methods

The employed methodological approaches include gene

expression analysis, comparative genomic hybridization

array, proteomic analysis, metabolic profiling, in vitro

radiobiological clonogenic survival assays, assessment of

the histone methylation marks and CSC marker expression,

analysis of DNA damage repair and oxidative stress

response. This study is based on the different models

including tumor cell lines and their radioresistant

derivatives, prostate cancer xenografts, ex vivo treated

tissues and analysis of the publicly available TCGA

prostate cancer datasets.

Results

Our study revealed that irradiation causes long-term

upregulation in the expression of stem cell markers and

induces tumor cell reprogramming. Furthermore,

radioresistant and tumorigenic cell populations undergo a

phenotypic switch during the course of radiotherapy. This

phenotypic plasticity is associated with genetic,

epigenetic and metabolic changes induced by irradiation.

Expression of CSC markers and proteins involved in

glutamine metabolism can be used to predict clinical

outcome of prostate cancer patients.

Conclusion

Our studies suggest that radioresistant properties of

prostate cancer cells are dynamic in nature and that

combination of irradiation with therapeutic agents which

prevent tumor cell reprogramming and metabolic switch

may restore the cytotoxic effects of irradiation in

radioresistant CSC populations.

References:

Cojoc M et al. Cancer Res. 2015; 75(7):1482-94;

Peitzsch C et al. Cancer Res. 2016; 76(9):2637-51;

Kurth I et al. Oncotarget 2015; 6(33):34494-509;

Krause M et al. Advanced Drug Delivery Reviews, 2016,

pii: S0169-409X(16)30052-7.

PV-0374 Molecular insights into a disease-relevant

DNA damage response pathway

B. Xu

Southern Research Institute, Molecular Radiation

Biology Laboratory, Birmingham, USA

Purpose or Objective

The optimal DNA damage response (DDR) is critical to

prevent genetic instability. The DDR is also critical to

promote cellular survival in response to DNA damage as

targeting optimal DDR pathways leads to sensitization to

radiotherapy. The Speckle type Poz Protein (SPOP), an E3

ubiquitin ligase adaptor, has recently been identified as

the gene that has the most common somatic point

mutations in prostate cancer.

SPOP

mutations are

associated with genomic alterations, indicating a role for

SPOP in the maintenance of genome stability. We, and

others, have recently demonstrated a critical role of SPOP

in the DDR, suggesting

SPOP

mutants may represent a

subgroup of patients that have hyper sensitivity to DNA

damaging therapies. However, how

SPOP

mutations might

impact its function and their roles in the progress of

prostate tumorigenesis remain to be extensively studied.

The objective of this research is to elucidate the

functional significnance of SPOP in the DNA damage

response pathways and to identify a subgroup of prostate

cancer patients that have distinctive radiotherapeutic

responses.

Material and Methods

Using computational modeling, we assessed the

importance of the Serine 119 residue in the SBC-MATH

domain. We characterized prostate cancer cells

expressing the S119N dominant negative mutation using

Western blot analysis, immunofluorescence microscopy,

flow cytometry, and radiosensitivity by colony formation

analysis. We also used

in situ

proximity ligation assay to

demonstrate the interaction of SPOP with ATM. By mass

spectrometry we identified a list of proteins that

displayed alterations in association with SPOP in response

to DNA damage.

Results

We found that Serine 119 resideing in the SBC-MATH

binding interface is in close contact with non-polar

residue of the SPOP-binding consensus motif. We found

that prostate cancer cells expressing mutation of S119

displayed impaired DNA damage responses. Using i

n situ

proximity ligation assay, we demonstrate that Serine 119

is essential for SPOP interaction with ATM. We show that

ATM phosphorylates SPOP on Serine 119 in response to DNA

damage. Characterization of the functional significance of

ATM-mediated SPOP phosphorylation indicates a wide

range of downstream targets regulating cell cycle

progression and DNA repair. By mass spectrometry we

have identified a list of proteins that displayed alterations

in association with SPOP in response to DNA damage. We

found that alterations of SPOP interaction with these

proteins are required for activation of the pathways

involved in cell cycle checkpoints and Non-Homologous

End Joining (NHEJ).