Genetic Variations in the PI3K/PTEN/AKT/mTOR Pathway are Associated with Clinical Outcomes

in Esophageal Cancer Patients Treated with Chemoradiotherapy

Michelle Hildebrandt, Ph.D.Instructor

Department of Epidemiology

Outline

• Pathway• Experimental Details• Results• Conclusions• Future Directions

PI3K/PTEN/AKT/mTOR Pathway

Downstream Processes

Manning and Cantley, Cell (2007)

mTOR

TERT

Major Effectors

• PI3K• PTEN• AKT• mTOR

PI3K and PTEN

• “Sensor” of cellular environment– PI3K activated by receptors at membrane

• RTK and GPCR

– Transmitted through PIP2/3

• PIP3 – on• PIP2 – off

– PTEN removes activation signal

AKT

• Major adaptor protein

• 3 isoforms (AKT1/2/3)• AKT1 and AKT2 most important for this pathway in

cancer

mTORmammalian Target Of Rapamycin (FRAP1)

• Involved in regulation of translation

Y Mamane, et al, Oncogene (2006)

Importance in Cancer

• Balance between cell survival and apoptosis– Activated Survival

• This pathway is often constitutively active in MANY cancers– Gene amplifications– Activating mutations– Silencing of PTEN no regulation

Chemotherapy Response

• In lung and ovarian cell lines:– Overexpression of PIK3CA and reduced PTEN

activity results in cisplatin resistance – Cisplatin resistance associated with AKT

overexpression– Inhibition of AKT increases efficacy of paclitaxel– Inhibition of mTOR increases cisplatin efficacy– Increased AKT activity found to increase response

to 5-FU

Esophageal Cancer

• Estimated >16,000 new EC cases each year in the US

• Rate of adenocarcinoma increasing rapidly– Mirror rates of obesity gastroreflux

• Surgery is standard treatment

• Multimodal approaches are often used– 5-year survival rate of 25-28%

Esophageal Cancer

• Phosphorylation of AKT increased during progression from Barrett’s to EC

• PI3K/PTEN/AKT/mTOR Pathway is activated in EC

The Question

• For EC patients treated with a taxane, fluoropyrimidine and/or platinum agent…

Is genetic variation within the PI3K/PTEN/AKT/mTOR pathway

associated with variation in clinical outcomes?

Experimental DetailsPatient Characteristics

• 186 Caucasian patients with resectable adenocarcinoma or squamous cell carcinoma

• Recruited between 1985 and 2003 at MDACC

• Concurrent chemoradiotherapy followed by surgery, or induction chemotherapy followed by concurrent chemoradiotherapy and then surgery

Experimental DetailsPatient Characteristics

Experimental DetailsPatient Characteristics

• Study endpoints were:– Overall Survival– Recurrence– Pathologic Response to Therapy

• Adjusted all analyses for:– Age at diagnosis, gender, smoking status, alcohol

consumption, clinical stage, histological tumor type, tumor location, pathological stage and histological viability, radiation dosage, chemoradiotherapy sequence, and chemotherapy regimens

Experimental DetailsTreatment Information

• Stratified analyses by chemotherapeutic regimen – Any of the three – Fluoropyrimidine + any– Platinum compound + any– Taxane + any

Experimental DetailsSNP Selection

• tagged SNP Selection – Based on HapMap data from CEPH population

• Gene + 5 Kb flanking

– LD tagged SNPs: r2 > 0.8, MAF > 0.1– tagger and LDselect

Experimental DetailsSNP Selection

Results

• 16 SNPs, 4 treatment groups, 3 clinical outcomes…

ResultsRecurrence Risk in Patients Treated with Any of the Three

• Three SNPs associated with recurrence– AKT1:rs2498804– AKT2:rs892119

• Increased risk of recurrence• All treatment groups

– PTEN:rs12357281• Decreased risk of recurrence• Except for platinum compound + any

0.0270.13 - 0.880.34 CG + GG

1 / 0GG

0.0270.13 - 0.890.3422 / 7CG

1(reference)95 / 49CC

PTEN:rs12357281

0.0011.64 - 6.663.30 AG + GG

0.2800.49 - 12.012.423 / 2GG

0.0011.66 - 7.283.4825 / 23AG

1(reference)95 / 33AA

AKT2:rs892119

0.0341.06 - 4.602.21 GT + TT

0.0371.07 - 9.613.218 / 7TT

0.0680.95 - 4.372.0463 / 30GT

1(reference)50 / 20GG

AKT1:rs2498804

p-value95% CIHR*No Recurrence /

Recurrence

ResultsRecurrence Risk in Patients Treated with Any of the Three

ResultsRecurrence-free Survival by AKT2:rs892119

A: Any Three

B: 5-FU

C: Platinum agent

D: Taxane

p-value95% CIHR*No Recurrence /

Recurrence

< 0.0012.34 - 18.186.5215 / 172

0.0241.15 - 7.192.8769 / 271

1 (reference)36 / 130

# of Unfavorable Genotypes

ResultsRecurrence Risk by Unfavorable Genotype

• AKT1:rs2498804 and AKT2:rs892119

Consistent across all strata:Fluoropyrimidine - HR*: 6.36

Platinum Agent - HR*: 10.73

Taxane - HR*: 83.37

ResultsGene-Gene Interactions in Patients Treated with a Taxane

• 7 SNPs associated with Recurrence

0.0080.006 - 0.4580.05CG + GG

PTEN:rs12357281

0.0311.20 - 42.36 7.13CC

PIK3CA:rs6443624

0.0151.60 - 80.8811.38TT

PIK3CA:rs7621329

0.0351.19 -128.3812.35TT

FRAP1:rs2295080

0.0061.62 - 16.885.23AG + GG

AKT2:rs892119

0.0161.55 - 76.9810.94TT

AKT1:rs1130214

0.0032.40 - 83.0214.10GT + TT

AKT1:rs2498804

p-value95% CIHR*

ResultsSurvival Tree Analysis for Recurrence

ResultsSurvival in Patients Treated with Any of the Three

• Both FRAP1 (mTOR) SNPs significant– Consistent except for platinum compound group

TaxanePlatinum

CompoundFluoropyrimidineAny of the

Three

0.0038.280.0732.660.00044.660.0014.19TT

FRAP1:rs2295080

0.0057.030.0912.770.0033.820.0043.53TT

FRAP1:rs11121704

p-valueHR*p-valueHR*p-valueHR*p-valueHR*

ResultsSurvival in Patients Treated with a Taxane

• AKT1 and AKT2 SNPs

0.0061.43 - 8.783.54AG + GG

0.0650.89 - 43.886.25GG

0.0141.27 - 8.403.27AG

1(reference)AA

AKT2:rs892119

0.1570.79 - 4.191.82GT + TT

0.0141.56 - 51.178.92TT

0.2220.73 - 3.941.69GT

1(reference)GG

AKT1:rs1130214

p-value95% CIHR*

ResultsPathologic Response to Therapy

• AKT2:rs892119

p-valueOR*p-valueOR*p-valueOR*p-valueOR*

TaxanePlatinum CompoundFluoropyrimidineAny of the Three

0.0264.120.0592.460.0082.980.0102.81AG + GG

GG

0.0423.680.1052.180.0182.680.0232.54AG

1 (reference) 1 (reference)1 (reference) 1 (reference)AA

ResultsPathologic Response to Therapy

• AKT1:rs3803304 in patients treated with Any of the Three– HR*: 0.50 (0.25 – 0.99), p-value: 0.049

• FRAP1:rs11121704 in taxane group only– HR*: 2.76 (1.04 – 7.37), p-value: 0.042

Conclusions

• Genetic variation within this important pathway is important…

• AKT2:rs892119 in particular– Tags 5 SNPs – Results suggest increased signaling– Functional SNP?

Conclusions

• PTEN variation had expected opposite effect– Counteracts other effects

• Differences between treatment groups– Many more in taxane group sample size?– Less in platinum compound group

Future Directions

• Analyze SNPs in a control group undergoing surgery alone

• Same in other cancers treated with these agents?

• Functional studies mechanism

Thank You!

Xifeng WuJafer Ajani

Julie Izzo

Mien-Chie Huang

Esophageal Study Participants

Wu Laboratory