PIK3CA Mutant Colorectal Cancer Research Articles

Abstract B03: Oncogenic PIK3CA mutations reprogram glutamine metabolism in colorectal cancers

Abstract Glutamine addiction is a major metabolic reprogramming event that occurs in cancer cells. Many tumors exhibit oncogene-dependent addiction to glutamine. PIK3CA, which encodes the p110 alpha catalytic subunit of phosphatidylinositol 3-kinase, is the most frequently mutated oncogene in human cancers. However, whether PIK3CA mutations reprogram cancer metabolism is an important unaddressed question. Using isogenic cell lines expressing either wild-type (WT) or oncogenic mutant allele of PIK3CA, we demonstrated that colorectal cancer cells harboring PIK3CA mutations are more dependent on glutamine to grow. In contrast, the isogenic PIK3CA WT and mutant cell lines did not show differential sensitivity to glucose deprivation. Through gene expression analyses, we showed that glutamate pyruvate transaminase 2 (GPT2) is up-regulated in the colorectal cancer cell lines with PIK3CA mutations compared to the isogenic cell lines expressing WT PIK3CA. We demonstrated that induction of GPT2 by mutant p110 alpha is necessary and sufficient to render colorectal cancer cells dependent on glutamine. Moreover, aminooxyacetate, which inhibits enzymatic activity of aminotransferases including GPT2, suppresses xenograft tumor growth of colorectal cancers with PIK3CA mutations, but not colorectal cancers with WT PIK3CA. Thus our data suggest that targeting glutamine metabolism may be an effective approach to treat colorectal cancer patients harboring PIK3CA mutations. Mutant p110 alpha up-regulates GPT2 gene expression through an AKT-independent PDK1-RSK2-ATF4 signaling axis. We showed that ATF4 is a transcription factor that activates GPT2 gene expression. We further demonstrated that mutant p110 alpha activates RSK2 kinase through PDK1. Activated RSK2 then phosphorylates ATF4 at the serine residue 245, which in turn recruits deubiquitinase USP8 and protects ATF4 from ubiquitin-mediated degradation. Lastly, using [13C5-]glutamine isotope-tracing technology, we showed that PIK3CA mutant colorectal cancer cells convert more glutamine to alpha-keto-glutarate to replenish the tricarboxylic acid cycle to generate ATP. Together, our data establish oncogenic PIK3CA mutations as a cause of glutamine addiction in colorectal cancers. Citation Format: Zhenghe Wang. Oncogenic PIK3CA mutations reprogram glutamine metabolism in colorectal cancers. [abstract]. In: Proceedings of the AACR Special Conference: Metabolism and Cancer; Jun 7-10, 2015; Bellevue, WA. Philadelphia (PA): AACR; Mol Cancer Res 2016;14(1_Suppl):Abstract nr B03.

Abstract C115: Targeting glutamine metabolism in colorectal cancers with PIK3CA mutations

Abstract Glutamine addiction is a major metabolic reprogramming event that occurs in cancer cells. Many tumors exhibit oncogene-dependent addiction to glutamine. PIK3CA, which encodes the p110α catalytic subunit of phosphatidylinositol 3-kinase α, is the most frequently mutated oncogene in human cancers. However, whether PIK3CA mutations reprogram cancer metabolism is an important unaddressed question. Here we show that oncogenic PIK3CA mutations render colorectal cancers (CRCs) more dependent on glutamine to growth. As a metabolite, glutamine is first converted glutamate by glutaminase (GLS) and then to α-ketoglutarate (α-KG) by either a transaminase or a glutamate dehydrogenase. Calithera Biosciences recently developed a potent GLS inhibitor called CB-839, which is currently in phase I clinical trials in cancer patients. Using isogenic colorectal cancer cell lines with either WT or mutant PIK3CA allele knockout, we demonstrated that CRCs with PIK3CA mutations are more sensitive to growth inhibition by CB-839. Remarkably, combination of CB-839 with 5-FU induces regression xenograft tumors from a CRC with a PIK3CA mutation, suggesting that this combinational therapy may be effective approach to treat CRC patients whose tumors harbor PIK3CA mutations. Mechanistically, mutant p110α up-regulates gene expression of glutamate pyruvate transaminase 2 (GPT2) in CRC cells, thereby facilitate conversion of glutamate to α-KG. Using [13C5-]glutamine isotope-tracing technology, we showed that PIK3CA mutant CRCs produce more α-KG from glutamine to α-KG to replenish the tricarboxylic acid (TCA) cycle to generate ATP. Moreover, aminooxyacetate, which inhibits enzymatic activity of transaminases including GPT2, suppresses xenograft tumor growth of CRCs with PIK3CA mutations, but not CRCs with WT PIK3CA. Mutant p110α up-regulates the transcription of GPT2 through an AKT-independent PDK1-RSK2-ATF4 signaling axis. We showed that ATF4 is a transcription factor that activates GPT2 gene expression. We further demonstrated that mutant p110α activates RSK2 kinase through PDK1. Activated RSK2 then phosphorylates ATF4 at the serine residue 245, which in turn recruits deubiquitinase USP8 and protects ATF4 from ubiquitin-mediated degradation. Together, our data establish oncogenic PIK3CA mutations as a cause of glutamine addiction in CRCs and that targeting glutamine metabolism may be effective approach to treat CRCs with PIK3CA mutations. Citation Format: Zhenghe John Wang, Yujun Hao. Targeting glutamine metabolism in colorectal cancers with PIK3CA mutations. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr C115.

Abstract 1125: Oncogenic PIK3CA mutations reprogram glutamine metabolism in colorectal cancers

Abstract Glutamine addiction is a major metabolic reprogramming event that occurs in cancer cells. Many tumors exhibit oncogene-dependent addiction to glutamine. PIK3CA, which encodes the p110α catalytic subunit of phosphatidylinositol 3-kinase α, is the most frequently mutated oncogene in human cancers. However, whether PIK3CA mutations reprogram cancer metabolism is an important unaddressed question. Here we show that oncogenic PIK3CA mutations reprogram glutamine metabolism by up-regulating glutamate pyruvate transaminase 2 (GPT2) in colorectal cancer (CRC) cells, thereby rendering them addicted to glutamine. We demonstrated that induction of GPT2 by mutant p110α is necessary and sufficient to render CRC cells addicted to glutamine. Moreover, aminooxyacetate, which inhibits enzymatic activity of aminotransferases including GPT2, suppresses xenograft tumor growth of CRCs with PIK3CA mutations, but not CRCs with WT PIK3CA. Thus our data suggest that targeting glutamine metabolism may be an effective approach to treat CRC patients harboring PIK3CA mutations. Mutant p110α up-regulates GPT2 gene expression through an AKT-independent PDK1-RSK2-ATF4 signaling axis. We showed that ATF4 is a transcription factor that activates GPT2 gene expression. We further demonstrated that mutant p110α activates RSK2 kinase through PDK1. Activated RSK2 then phosphorylates ATF4 at the serine residue 245, which in turn recruits deubiquitinase USP8 and protects ATF4 from ubiquitin-mediated degradation. Lastly, using [13C5-]glutamine isotope-tracing technology, we showed that PIK3CA mutant CRCs convert more glutamine to α-keto-glutarate to replenish the tricarboxylic acid (TCA) cycle to generate ATP. Together, our data establish oncogenic PIK3CA mutations as a cause of glutamine addiction in CRCs. Citation Format: Yujun Hao, Yardena Samuels, Qingling Li, Dawid Krokowski, Henri Brunengraber, Maria Hatzoglou, Guo-Fang Zhang, Bert Vogelstein, Zhenghe Wang. Oncogenic PIK3CA mutations reprogram glutamine metabolism in colorectal cancers. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1125. doi:10.1158/1538-7445.AM2015-1125

PIK3CA Somatic Mutation Status in Relation to Patient and Tumor Factors in Racial/Ethnic Minorities with Colorectal Cancer.

Approximately 10% to 20% of colorectal cancers exhibit somatic mutations in the phosphoinositide-3-kinase, catalytic, alpha polypeptide gene (PIK3CA). We evaluated the relationship of PIK3CA mutation status in colorectal cancer with race/ethnicity, colorectal cancer survival, and other patient and tumor factors. This study comprised 377 racial/ethnic minorities with incident invasive colorectal cancer, enrolled in the Colon Cancer Family Registry via population-based cancer registries. Tumor specimens were tested for PIK3CA mutations in exon 9 and 20 hotspots, BRAF p.V600E mutations, and DNA mismatch repair (MMR). In logistic regression models, we evaluated the association between PIK3CA mutation status and race/ethnicity, overall, and by mutation site. Using Cox regression, we evaluated the association between PIK3CA mutation status and survival after colorectal cancer diagnosis. PIK3CA mutations were detected in 42 cases (11%), with a similar prevalence across racial/ethnic groups. Individuals with PIK3CA-mutated colorectal cancer were significantly more likely than those with PIK3CA-wildtype disease to have proximal colon cancer, MMR-deficient tumors, and a germline MMR mutation (P ≤ 0.01). There was no evidence for an association between PIK3CA and overall survival (HR, 0.77; 95% confidence interval, 0.43-1.39). The prevalence of PIK3CA mutation status in colorectal cancer does not differ according to race/ethnicity, but may vary according to other relevant clinicopathologic and etiologic factors, including germline MMR mutation status, tumor MMR status, and tumor site. These findings underscore the importance of PIK3CA mutation status in colorectal cancer epidemiology and provide evidence that the prevalence of such mutations is similar across several racial/ethnic groups.

Combined inhibition of MEK and Aurora A kinase in KRAS/PIK3CA double-mutant colorectal cancer models.

Aurora A kinase and MEK inhibitors induce different, and potentially complementary, effects on the cell cycle of malignant cells, suggesting a rational basis for utilizing these agents in combination. In this work, the combination of an Aurora A kinase and MEK inhibitor was evaluated in pre-clinical colorectal cancer models, with a focus on identifying a subpopulation in which it might be most effective. Increased synergistic activity of the drug combination was identified in colorectal cancer cell lines with concomitant KRAS and PIK3CA mutations. Anti-proliferative effects were observed upon treatment of these double-mutant cell lines with the drug combination, and tumor growth inhibition was observed in double-mutant human tumor xenografts, though effects were variable within this subset. Additional evaluation suggests that degree of G2/M delay and p53 mutation status affect apoptotic activity induced by combination therapy with an Aurora A kinase and MEK inhibitor in KRAS and PIK3CA mutant colorectal cancer. Overall, in vitro and in vivo testing was unable to identify a subset of colorectal cancer that was consistently responsive to the combination of a MEK and Aurora A kinase inhibitor.

Impact of regular aspirin use on overall and cancer-specific survival in patients with colorectal cancer harboring a PIK3CA mutation

Background. Recent data have suggested that regular aspirin use improves overall and cancer-specific survival in the subset of colorectal cancer (CRC) patients harboring PIK3CA mutations. However, the number of PIK3CA-mutated CRC patients examined in these studies was modest. Our collaborative study aims to validate the association between regular aspirin use and survival in patients with PIK3CA-mutated CRC.Patients and methods. Patients with PIK3CA-mutated CRC were identified at Moffitt Cancer Center (MCC) in the United States and Royal Melbourne Hospital (RMH) in Australia. Prospective clinicopathological data and survival data were available. At MCC, PIK3CA mutations were identified by targeted exome sequencing using the Illumina GAIIx Next Generation Sequencing platform. At RMH, Sanger sequencing was utilized. Multivariate survival analyses were conducted using Cox logistic regression.Results. From a cohort of 1487 CRC patients, 185 patients harbored a PIK3CA mutation. Median age of patients with PIK3CA-mutated tumors was 72 years (range: 34–92) and median follow up was 54 months. Forty-nine (26%) patients used aspirin regularly. Regular aspirin use was not associated with improved overall survival (multivariate HR 0.96, p = 0.86). There was a trend towards improved cancer-specific survival (multivariate HR 0.60, p = 0.14), but this was not significant.Conclusions. Despite examining a large number of patients, we did not confirm that regular aspirin use was associated with statistically significant improvements in survival in PIK3CA-mutated CRC patients. Prospective evaluation of this relationship is warranted.

XIAP-targeting drugs re-sensitize PIK3CA-mutated colorectal cancer cells for death receptor-induced apoptosis.

Mutations in the oncogenic PIK3CA gene are found in 10–20% of colorectal cancers (CRCs) and are associated with poor prognosis. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and agonistic TRAIL death receptor antibodies emerged as promising anti-neoplastic therapeutics, but to date failed to prove their capability in the clinical setting as especially primary tumors exhibit high rates of TRAIL resistance. In our study, we investigated the molecular mechanisms underlying TRAIL resistance in CRC cells with a mutant PIK3CA (PIK3CA-mut) gene. We show that inhibition of the constitutively active phosphatidylinositol-3 kinase (PI3K)/Akt signaling pathway only partially overcame TRAIL resistance in PIK3CA-mut-protected HCT116 cells, although synergistic effects of TRAIL plus PI3K, Akt or cyclin-dependent kinase (CDK) inhibitors could be noted. In sharp contrast, TRAIL triggered full-blown cell death induction in HCT116 PIK3CA-mut cells treated with proteasome inhibitors such as bortezomib and MG132. At the molecular level, resistance of HCT116 PIK3CA-mut cells against TRAIL was reflected by impaired caspase-3 activation and we provide evidence for a crucial involvement of the E3-ligase X-linked inhibitor of apoptosis protein (XIAP) therein. Drugs interfering with the activity and/or the expression of XIAP, such as the second mitochondria-derived activator of caspase mimetic BV6 and mithramycin-A, completely restored TRAIL sensitivity in PIK3CA-mut-protected HCT116 cells independent of a functional mitochondrial cell death pathway. Importantly, proteasome inhibitors and XIAP-targeting agents also sensitized other CRC cell lines with mutated PIK3CA for TRAIL-induced cell death. Together, our data suggest that proteasome- or XIAP-targeting drugs offer a novel therapeutic approach to overcome TRAIL resistance in PIK3CA-mutated CRC.

Regular aspirin (ASA) use and survival in patients with PIK3CA-mutated metastatic colorectal cancer (CRC).

386 Background: Recent data has demonstrated that regular ASA use improves overall and cancer-specific survival in the subset of CRC patients harboring PIK3CA mutations. However, as this series only analyzed 15 PIK3CA mutant CRC patients with metastatic disease at diagnosis, it remains uncertain whether the survival benefit associated with regular ASA use extends to patients with metastatic disease. We combined data from two large academic institutions to explore the association between regular ASA use and survival in metastatic CRC. Methods: Patients with PIK3CA mutated CRC were identified at Moffitt Cancer Center (MCC) in Tampa, FL and Royal Melbourne Hospital (RMH) in Australia. Prospective clinicopathological data (including age, sex, site of disease) and survival data were available. At MCC, PIK3CA mutations were identified by exome sequencing using an Illumina Next Generation Sequencing platform with 50-100X coverage. At RMH, Sanger sequencing was used to identify PIK3CA mutations. Survival analyses were conducted using Cox regression. Results: We identified 187 CRC patients who harbored a PIK3CA mutation. Median age was 72 years and median follow up was 48 months. 49 (26%) patients used ASA regularly. 47 (25%) patients had metastatic disease at diagnosis. In univariate analyses, regular ASA use was not associated with improved overall survival (HR 0.87, p = 0.60), although there was a trend towards improved cancer-specific survival (HR 0.48, p = 0.06). In patients with stage-II or stage-III disease, regular ASA use did not improve overall, cancer-specific or recurrence-free survival. However, in stage-IV patients, regular ASA use was significantly associated with improved overall (HR 0.35, p = 0.04) and cancer-specific (HR 0.28, p = 0.02) survival in a univariate analysis. Conclusions: Our study demonstrates that in patients with metastatic CRC harboring a PIK3CA mutation, regular ASA use is associated with a significant overall and cancer-specific survival advantage. However, we were not able to confirm the survival advantage across all stages. To our knowledge, our study is the largest to examine ASA use in PIK3CA mutated CRC.

Target-Based Therapeutic Matching in Early-Phase Clinical Trials in Patients with Advanced Colorectal Cancer and PIK3CA Mutations

Target-matched treatment with PI3K/AKT/mTOR pathway inhibitors in patients with diverse advanced cancers with PIK3CA mutations have shown promise. Tumors from patients with colorectal cancer were analyzed for PIK3CA, KRAS, and BRAF mutations. PIK3CA-mutated tumors were treated, whenever feasible, with agents targeting the PI3K/AKT/mTOR pathway. Of 194 patients analyzed, 31 (16%) had PIK3CA mutations and 189 (97%) were assessed for KRAS mutations. Patients with PIK3CA mutations had a higher prevalence of simultaneous KRAS mutations than patients with wild-type PIK3CA (71%, 22/31 vs. 43%, 68/158; P = 0.006). Of 31 patients with PIK3CA mutations, 17 (55%) were treated with protocols containing PI3K/AKT/mTOR pathway inhibitors [median age, 57 years; median number of prior therapies, 4; mTORC1 inhibitors (11), phosphoinositide 3-kinase (PI3K) inhibitors (5), or an AKT inhibitor (1)]. None (0/17) had a partial or complete response (PR/CR) and only 1 [6%, 95% confidence interval (CI), 0.01-0.27] had stable disease 6 months or more, which was not significantly different from a stable disease ≥6 month/PR/CR rate of 16% (11/67; 95% CI, 0.09-0.27) in patients with colorectal cancer without PIK3CA mutations treated with PI3K/AKT/mTOR pathway inhibitors (P = 0.44). Median progression-free survival was 1.9 months (95% CI, 1.5-2.3). In conclusion, our data provide preliminary evidence that in heavily pretreated patients with PIK3CA-mutant advanced colorectal cancer, protocols incorporating PI3K/AKT/mTOR inhibitors have minimal activity. PIK3CA mutations are associated with simultaneous KRAS mutations, possibly accounting for therapeutic resistance.

Aspirin Therapy for Colorectal Cancer With PIK3CA Mutation: Simply Complex!

Prospective observational studies and randomized clinical trials have demonstrated that regular use of aspirin and selective cyclooxygense-2 (COX-2) inhibitors reduces the risk of developing colorectal cancer (CRC) and adenoma. More recently, large observational studies have suggested that regular aspirin use may also be associated with improved survival among patients with established CRC. The mechanisms by which aspirin influences CRC risk and possibly survival are poorly understood. COX-2 (or prostaglandinendoperoxide synthase 2 [PTGS2]) promotes inflammation and cell proliferation, and most adenomas and CRCs overexpress this enzyme. Previous studies have reported that aspirin may preferentially reduce the risk of COX-2–expressing CRC and also preferentially improve the survival of patients with CRC with COX-2–expressing tumors. Nonetheless, in laboratory models, aspirin seems to decrease proliferation and increase apoptosis in CRC cell lines without detectable COX activity. Ongoing studies have sought to define the molecular basis for the effect of aspirin on CRC risk and progression. In a large observational study of patients with CRC, Liao et al found that aspirin conferred improved survival in patients with PIK3CA-mutated CRC, but not among those with PIK3CA–wild-type tumors. In the report accompanying our article in Journal of Clinical Oncology, Domingo et al similarly observe a preferential benefit for aspirin in PIK3CA-mutated CRC in a large randomized trial of rofecoxib in patients with stage II/III CRC (VICTOR [Vioxx in Colorectal Cancer Therapy: Definition of Optimal Regime] trial), potentially moving us closer to clinical use of PIK3CA mutation as a predictive biomarker for aspirin use in patients with CRC. Here, we review some of the relevant complex relationships between aspirin, phosphatidylinositol 3-kinase (PI3K) signaling, and other cellular interactions.

Evaluation of PIK3CA Mutation As a Predictor of Benefit From Nonsteroidal Anti-Inflammatory Drug Therapy in Colorectal Cancer

Aspirin and other nonsteroidal anti-inflammatory drugs (NSAIDs) protect against colorectal cancer (CRC) and are associated with reduced disease recurrence and improved outcome after primary treatment. However, toxicities of NSAIDs have limited their use as antineoplastic therapy. Recent data have suggested that the benefit of aspirin after CRC diagnosis is limited to patients with PIK3CA-mutant cancers. We sought to determine the predictive utility of PIK3CA mutation for benefit from both cyclooxygenase-2 inhibition and aspirin. We performed molecular analysis of tumors from 896 participants in the Vioxx in Colorectal Cancer Therapy: Definition of Optimal Regime (VICTOR) trial, a large randomized trial comparing rofecoxib with placebo after primary CRC resection. We compared relapse-free survival and overall survival between rofecoxib therapy and placebo and between the use and nonuse of low-dose aspirin, according to tumor PIK3CA mutation status. We found no evidence of a greater benefit from rofecoxib treatment compared with placebo in patients whose tumors had PIK3CA mutations (multivariate adjusted hazard ratio [HR], 1.2; 95% CI, 0.53 to 2.72; P = .66; (P)INTERACTION = .47) compared with patients with PIK3CA wild-type cancers (HR, 0.87; 95% CI, 0.64 to 1.16; P = .34). In contrast, regular aspirin use after CRC diagnosis was associated with a reduced rate of CRC recurrence in patients with PIK3CA-mutant cancers (HR, 0.11; 95% CI, 0.001 to 0.832; P = .027; (P)INTERACTION = .024) but not in patients lacking tumor PIK3CA mutation (HR, 0.92; 95% CI, 0.60 to 1.42; P = .71). Although tumor PIK3CA mutation does not predict benefit from rofecoxib treatment, it merits further evaluation as a predictive biomarker for aspirin therapy. Our findings are concordant with recent data and support the prospective investigation of adjuvant aspirin in PIK3CA-mutant CRC.

Descriptive profile of PIK3CA-mutated colorectal cancer in postmenopausal women

Approximately 10-30 % of colorectal cancers exhibit somatic mutations in the phosphoinositide-3-kinase, catalytic, alpha polypeptide gene (PIK3CA). We evaluated the relationship between PIK3CA mutation status and demographic factors, lifestyle factors, and other tumor characteristics and the relationship between PIK3CA mutation status and colorectal cancer survival. The population-based study included postmenopausal women with invasive colorectal cancer diagnosed between 1998 and 2002 in Western Washington State. Participants were interviewed, and tumor specimens were tested for PIK3CA mutations in exons 9 and 20 hotspots, KRAS exon 2 mutations, BRAF p.V600E mutation, and microsatellite instability. We used Cox regression to evaluate the association between PIK3CA mutation status and disease-specific and overall survival. Stratified analyses were conducted by KRAS mutation status. PIK3CA mutations were evident in approximately 13 % of cases (N = 35). Women with PIK3CA-mutated colorectal cancer were significantly more likely than those with PIK3CA wild-type disease to be non-white, to have proximal colon cancer, and to have KRAS-mutated tumors (p < 0.05). In Cox proportional hazards regression analyses, overall survival was poorer, although not statistically significantly so, for women with PIK3CA-mutated versus wild-type colorectal cancer (hazard ratio = 1.74, 95 % confidence interval 0.86-3.50). This association between PIK3CA mutation status and survival was evident only when analyses were restricted to cases without somatic KRAS mutations (hazard ratio = 2.94, 95 % confidence interval 1.12-7.73). PIK3CA-mutated colorectal cancer appears to have a distinct epidemiologic profile that is of clinical significance. Women with PIK3CA-mutated colorectal cancer experience a poorer prognosis than those with PIK3CA wild-type disease.

Aspirin use and survival outcomes in patients (pts) with PIK3CA mutant colorectal cancer (CRC).

3598 Background: Aspirin has an established role in preventing CRC. Recent data suggests aspirin use may also benefit a subset of pts diagnosed with CRC. In one series, the authors identified PIK3CA mutations as a potential predictive biomarker for aspirin use, reporting that PIK3CA mutant CRC pts receiving aspirin had superior cancer specific survival (CSS) compared to those not receiving aspirin (HR 0.18, p&lt;0.001), whereas in pts with wildtype PIK3CA, aspirin had no survival impact. Our study aims to confirm the survival benefit associated with aspirin use in pts with PIK3CA mutant CRC. Methods: A cohort of CRC pts with PIK3CA mutations (Sanger sequencing) was identified. Prospectively collected clinicopathological, treatment and outcome data was available. Aspirin use was confirmed by chart review. CSS and overall survival (OS) analyses were conducted using Cox proportional hazards in univariate and multivariate settings. Recurrence free survival (RFS) analyses were limited to early stage CRC pts (Stage A-C). Statistical differences in 5-year CSS (5YS) rates were calculated using Fisher’s exact test. Results: From a cohort of 1,019 CRC pts with known PIK3CA mutation status, 121 (12%) harbored PIK3CA mutations. Of these, 112 (92%) had aspirin usage data available: 27 (24%) pts used aspirin, 85 (76%) did not. In the aspirin group, there were 22 (81%) early stage and 5 (19%) metastatic CRC pts; in the no-aspirin group, there were 59 (69%) early stage and 26 (31%) metastatic CRC pts. In univariate analyses, aspirin use was not associated with superior CSS (HR 0.57, p=0.21), OS (HR 0.83, p=0.57), or RFS (HR 0.72, p=0.57). In multivariate analyses, aspirin use was not associated with improved OS (HR 1.07, p=0.86), CSS (HR 1.04, p=0.94) or RFS (HR 0.54, p=0.34). In 69 (62%) pts with mature follow-up, there was a trend towards superior 5YS for aspirin users (69% v 42%, p=0.09), but this may reflect imbalances in stage at diagnosis. Conclusions: Our study was unable to confirm the recently reported survival benefit associated with aspirin use in pts with PIK3CA mutant CRC. Given the small numbers of pts, a modest survival benefit associated with aspirin use cannot be excluded. Analyses in an expanded cohort of early stage pts are underway.

Combination of TNF-α and graphene oxide-loaded BEZ235 to enhance apoptosis of PIK3CA mutant colorectal cancer cells.

The PI3K-AKT-mTOR pathway plays an important role in tumor cell growth, invasion, migration and apoptosis. A blockade of this signaling pathway has arisen as a compelling target for the tumor therapy. However, there is cross-talking between different signal pathways. Combined treatment of tumors with different signal pathway inhibitors is considered as an efficient strategy for cancer therapy. NVP-BEZ235 is a dual pan-class I PI3K and mTOR kinase inhibitor currently in clinical trial. TNF-α is involved in the regulation of cell apoptosis. In the current work, we explored the combined use of BEZ235 and TNF-α on the PIK3CA mutant colorectal cancer (CRC) cell proliferation inhibition. In our strategy, the BEZ235 is loaded on PEGylated graphene oxide (GO-PEG) by physisorption viaπ-π stacking to enhance its aqueous solubility. The resulting GO-BEZ235 complex exhibited excellent aqueous solubility while retaining a high cancer cell killing potency. The combination of BEZ235 and TNF-α shows an enhanced cellular proliferation inhibition for HCT 116 through enhancing the G1 phase arrest and cell apoptosis compared to either drug alone. Moreover, our experiments reveal that the enhanced tumor cell apoptosis depends on the activation of caspase-9, caspase-8 and caspase-3 mediated by the increased phosphorylation level of JNK. Taken together, our findings demonstrate for the first time the feasibility of BEZ235 delivered by GO-PEG and of the combined use of BEZ235 and TNF-α for PIK3CA mutant CRC therapy.

PIK3CA Mutations Predict for Response to Aspirin Therapy

Abstract Aspirin use selectively prolonged survival in patients with PIK3CA-mutant colorectal cancer.

Aspirin for PIK3CA-mutated colorectal cancer

Regular aspirin use after diagnosis could significantly increase survival of patients with colorectal cancer with mutated PIK3CA, the gene encoding the α catalytic subunit of phosphoinositide-3-kinase in the PI3K signalling pathway. PIK3CA mutations occur in almost 20% of colorectal tumours.

Target-based therapeutic matching in early-phase clinical trials in patients with advanced colorectal cancer and PIK3CA mutations.

459 Background: Therapeutic matching based on underlying molecular abnormalities showed promising results in patients with diverse advanced cancers in early phase clinical trials. PIK3CA mutations may predict response to therapies with PI3K/AKT/mTOR inhibitors. Methods: Tumors from patients with colorectal cancer referred to the Clinical Center for Targeted Therapy (Phase I Program) were analyzed for PIK3CA mutations. Patients with PIK3CA mutations were treated, whenever feasible, with agents targeting the PI3K/AKT/mTOR pathway. Results: Of 194 patients analyzed, 31 (16%) had PIK3CA mutations. Of 194 patients 175 (90%) were assessed for the presence of KRAS mutation. Patients with PIK3CA mutations had higher prevalence of simultaneous KRAS mutations than patients with wild-type (wt) PIK3CA (21/30, 70% vs. 63/145, 43%; p=0.009). Of the 31 patients with PIK3CA mutations, 17 (55%) were treated in clinical trials containing a PI3K/AKT/mTOR pathway inhibitor (median age, 57; median number of prior therapies, 4). Of these 17 patients, none achieved a partial or complete response (PR/CR) and only 1 (6%, 95% CI 0.01-0.27) patient had stable disease for more than 6 months (SD&gt;6), which was not significantly different from the SD&gt;6/PR/CR rate of 16% (11/67; 95% CI 0.09-0.27) in colorectal cancer patients without PIK3CA mutations treated on the same protocols targeting the PI3K/AKT/mTOR pathway (p=0.44). The median progression-free survival was only 1.9 months (95% CI 1.5-2.3). Conclusions: Heavily pretreated patients with PIK3CA-mutant advanced colorectal cancer do not seem to benefit from protocols incorporating PI3K/AKT/mTOR inhibitors. PIK3CA mutations are associated with simultaneous KRAS mutations, which might account for therapeutic resistance.