Inhibition of the mammalian target of rapamycin (mTOR) in advanced pancreatic cancer: results of two phase II studies.
BACKGROUND
The phosphoinositide 3-kinase (PI3K)/Akt pathway is constitutively activated in pancreatic cancer and the mammalian target of rapamycin (mTOR) kinase is an important mediator for its signaling. Our recent in vitro studies suggest that prolonged exposure of pancreatic cancer cells to mTOR inhibitors can promote insulin receptor substrate-PI3K interactions and paradoxically increase Akt phosphorylation and cyclin D1 expression in pancreatic cancer cells (negative feedback loop). The addition of erlotinib to rapamycin can down-regulate rapamycin-stimulated Akt and results in synergistic antitumor activity with erlotinib in preclinical tumor models.


METHODS
Two studies prospectively enrolled adult patients with advanced pancreatic cancer, Eastern Cooperative Oncology Group performance status 0-1, adequate hematologic, hepatic and renal parameters and measurable disease. In Study A, temsirolimus was administered intravenously at 25 mg weekly. In Study B, everolimus was administered orally at 30 mg weekly and erlotinib was administered at 150 mg daily. The primary endpoint in both studies was overall survival at 6 months. Secondary endpoints included time to progression, progression-free survival, overall survival, response rate, safety and toxicity. Pretreatment tumor biopsies were analyzed by immunofluorescence and laser scanning cytometry for the expression of pmTOR/mTOR, pAkt/Akt, pErk/Erk, pS6, p4EBP-1 and PTEN.


RESULTS
Five patients enrolled in Study A; Two patients died within a month (rapid disease progression and hemorrhagic stroke, respectively). One patient developed dehydration and another developed asthenia. Sixteen patients enrolled in Study B.: 12 males, all ECOG PS = 1. Median cycles = 1 (range 1-2). Grade 4 toxicity: hyponatremia (n = 1), Grade 3: diarrhea (n = 1), cholangitis (n = 3), hyperglycemia (n = 1), fatigue (n = 1). Grade 2: pneumonia (n = 2), dehydration (n = 2), nausea (n = 2), neutropenia (n = 1), mucositis (n = 2) & rash (n = 2). Four patients were hospitalized. Progressive disease occurred in 15 and 1 was non-evaluable. Pretreatment biopsies revealed a higher pAkt/Akt ratio in tumor specimens that in nonmalignant pancreatic tissue. No such trends were noted for the other biomarkers.


CONCLUSIONS
Neither study with mTOR inhibitors demonstrated objective responses or disease stability. The negative feedback loop resulting from mTOR inhibition may account for the disease progression and toxicity noted in these studies. Future strategies should aim for a broader targeting of the PI3K pathway in pancreatic cancer.


BACKGROUND



BACKGROUND



METHODS
NCT 0075647.
NCT00640978.
Javle
Milind M
MM
Department of Gastrointestinal Medical Oncology, UT-M D Anderson Cancer Center, Houston, TX, USA. mjavle@mdanderson.org
Shroff
Rachna T
RT
Xiong
Henry
H
Varadhachary
Gauri A
GA
Fogelman
David
D
Reddy
Shrikanth A
SA
Davis
Darren
D
Zhang
Yujian
Y
Wolff
Robert A
RA
Abbruzzese
James L
JL
D000230:Adenocarcinoma / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology; D000328:Adult; D000368:Aged; D000971:Antineoplastic Combined Chemotherapy Protocols; D014408:Biomarkers, Tumor / Q000378:metabolism*; D066246:ErbB Receptors / Q000037:antagonists & inhibitors; D000069347:Erlotinib Hydrochloride; D000068338:Everolimus; D005260:Female; D005455:Fluorescent Antibody Technique; D006801:Humans; D007124:Immunoenzyme Techniques; D007166:Immunosuppressive Agents / Q000627:therapeutic use; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D010190:Pancreatic Neoplasms / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology; D010766:Phosphorylation; D011379:Prognosis; D011446:Prospective Studies; D047428:Protein Kinase Inhibitors / Q000627:therapeutic use; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D011799:Quinazolines / Q000627:therapeutic use; D015398:Signal Transduction; D020123:Sirolimus / Q000031:analogs & derivatives / Q000627:therapeutic use; D015996:Survival Rate; D058570:TOR Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*
D014408:Biomarkers, Tumor; D007166:Immunosuppressive Agents; D047428:Protein Kinase Inhibitors; D011799:Quinazolines; C401859:temsirolimus; D000068338:Everolimus; D000069347:Erlotinib Hydrochloride; C546842:MTOR protein, human; D066246:ErbB Receptors; D051057:Proto-Oncogene Proteins c-akt; D058570:TOR Serine-Threonine Kinases; D020123:Sirolimus