Wt PIK3CA Research Articles

Leptin and insulin synergize with PIK3CA mutation to enhance PD-L1 mediated immunosuppression in thyroid cancer

The incidence of thyroid cancer keeps rising and obesity emerges as an important risk factor for thyroid cancer, but the underlying mechanism is far from clear. Here, we hypothesize that leptin and insulin, two hormones closely related to obesity, may contribute to the pathogenesis of thyroid cancer. By using a combination of assays like CRISPR KO, cancer cell-T cell co-culture, ApoLive-Glo™ multiplex assay and syngeneic mouse model, we show that PD-L1 protein levels are increased dose-dependently by leptin or insulin in multiple thyroid cancer cell lines. Leptin and insulin converge to activate the PI3K-AKT pathway to enhance PD-L1 expression and activity. In addition, we use CRISPR KO to generate human thyroid cancer cells expressing WT PIK3CA or PIK3CA-E545K mutant. PIK3CA- E545K mutation makes the thyroid cancer cells to produce more PD-L1 protein upon leptin or insulin treatment. Thus, leptin and insulin synergize with PIK3CA mutation to enhance PD-L1 expression. Dual blockade of leptin and insulin signaling pathways reduces tumor size in a syngeneic mouse model. Our study suggests that understanding the interaction between genetic mutation and obesity is crucial for comprehensively assessing thyroid cancer risk and developing effective treatment strategies.

Nuclear translocation of p85\u03b2 promotes tumorigenesis of PIK3CA helical domain mutant cancer

PI3Ks consist of p110 catalytic subunits and p85 regulatory subunits. PIK3CA, encoding p110α, is frequently mutated in human cancers. Most PIK3CA mutations are clustered in the helical domain or the kinase domain. Here, we report that p85β disassociates from p110α helical domain mutant protein and translocates into the nucleus through a nuclear localization sequence (NLS). Nuclear p85β recruits deubiquitinase USP7 to stabilize EZH1 and EZH2 and enhances H3K27 trimethylation. Knockout of p85β or p85β NLS mutant reduces the growth of tumors harboring a PIK3CA helical domain mutation. Our studies illuminate a novel mechanism by which PIK3CA helical domain mutations exert their oncogenic function. Finally, a combination of Alpelisib, a p110α-specific inhibitor, and an EZH inhibitor, Tazemetostat, induces regression of xenograft tumors harboring a PIK3CA helical domain mutation, but not tumors with either a WT PIK3CA or a PIK3CA kinase domain mutation, suggesting that the drug combination could be an effective therapeutic approach for PIK3CA helical domain mutant tumors.

Abstract PS5-44: Pik3ca mutations among hormone receptor positive and HER-2 negative advanced breast cancer patients in Finland

Abstract Background: Several new medicinal products have been introduced for the treatment of advanced breast cancer (aBC) in recent years, many of which are indicated for a specific patient population. One of these compounds is alpelisib, a phosphatidylinositol 3-kinase (PI3K) inhibitor, which has shown efficacy in the treatment of hormone receptor positive and human epidermal growth factor receptor 2 negative (HR+/HER2-) advanced breast cancer (aBC) harboring phosphatidylinositol 4,5-bisphosphate 3-kinase catalytic subunit alpha (PIK3CA) “hotspot” mutations, i.e. mutations affecting the helical (E542K and E545K) and kinase (H1047R) domains. In this retrospective register-based study, the frequency of PIK3CA gene mutations as well as survival among HR+/HER2- aBC patients in Finland was analyzed. Methods: This study utilized retrospective register-based data from the Hospital District of Southwest Finland (Auria Biobank), which covers approximately 20% of the population in Finland. Patients diagnosed with aBC between 2004─2013 were identified using ICD-10 code C50* (breast cancer) together with customized text mining algorithms to extract metastatic patients. Tumor biomarker data including estrogen receptor (ER), progesterone receptor (PR), and HER2 status were used to identify HR+/HER2- patients. The formalin fixed paraffin embedded (FFPE) tumor tissue samples available for these patients in the Auria Biobank’s tissue archives were screened for PIK3CA mutations with next generation sequencing. Study follow-up period was defined to start from the date of aBC diagnosis and to continue until death or end of 2016, whichever occurred first. Clinical pathology and survival data were collected from the Auria Biobank and electronic medical records of the Hospital District of Southwest Finland. Overall survival (OS) was estimated using the Kaplan-Meier method. Results: Altogether 444 adult female patients with aBC were identified. HR and HER2 status were available for 377 patients (85%), out of which 274 (73%) were HR+/HER2-. Representative FFPE tumor samples were available for 187 patients and PIK3CA was successfully screened in 161 patients. Out of the sequenced HR+/HER2- samples, 53.4% showed mutation in the PIK3CA gene and 46.6% wild type (wt) PIK3CA gene. Approximately one third (32.3% n=52) of the samples represented PIK3CA hotspot mutations and 18% (n=29) of these displayed more than one PIK3CA variant. The most common PIK3CA hotspot mutation was H1047R. HR+/HER2- patients with the wt PIK3CA gene showed slightly shorter OS compared to patients showing PIK3CA hotspot mutations (18.9 months (95% CI: 14.1-25.1) vs. 22.3 months (95% CI: 17.0-26.3). Higher portion of the wt patients also developed metastases within 1 year from the primary diagnosis compared to the patients with PIK3CA hotspot mutations (41.3% vs. 25.0%). At the time of diagnosis, 92.0% of the wt and 84.6% of the PIK3CA hotspot mutated population was 50 years or older, respectively. Conclusion: Approximately one third of the HR+/HER2- aBC patient cohort in Finland had at least one variant of PIK3CA hotspot mutations in line with the SOLAR-1 clinical trial population. The OS did not differ markedly between the patients with wt and hotspot mutated PIK3CA gene. The short OS of the patients is probably due to the fact that the patients were treated before the availability of CDK4/6is as a treatment option. Citation Format: Krista Heinolainen, Silva Saarinen, Antti Ellonen, Antti Karlsson, Meri Utriainen, Simona Vertuani, Barbro Holm. Pik3ca mutations among hormone receptor positive and HER-2 negative advanced breast cancer patients in Finland [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS5-44.

Lysine-Specific Demethylase 1 Mediates AKT Activity and Promotes Epithelial-to-Mesenchymal Transition in PIK3CA-Mutant Colorectal Cancer.

Activation of the epithelial-to-mesenchymal transition (EMT) program is a critical mechanism for initiating cancer progression and migration. Colorectal cancers contain many genetic and epigenetic alterations that can contribute to EMT. Mutations activating the PI3K/AKT signaling pathway are observed in >40% of patients with colorectal cancer contributing to increased invasion and metastasis. Little is known about how oncogenic signaling pathways such as PI3K/AKT synergize with chromatin modifiers to activate the EMT program. Lysine-specific demethylase 1 (LSD1) is a chromatin-modifying enzyme that is overexpressed in colorectal cancer and enhances cell migration. In this study, we determine that LSD1 expression is significantly elevated in patients with colorectal cancer with mutation of the catalytic subunit of PI3K, PIK3CA, compared with patients with colorectal cancer with WT PIK3CA. LSD1 enhances activation of the AKT kinase in colorectal cancer cells through a noncatalytic mechanism, acting as a scaffolding protein for the transcription-repressing CoREST complex. In addition, growth of PIK3CA-mutant colorectal cancer cells is uniquely dependent on LSD1. Knockdown or CRISPR knockout of LSD1 blocks AKT-mediated stabilization of the EMT-promoting transcription factor Snail and effectively blocks AKT-mediated EMT and migration. Overall, we uniquely demonstrate that LSD1 mediates AKT activation in response to growth factors and oxidative stress, and LSD1-regulated AKT activity promotes EMT-like characteristics in a subset of PIK3CA-mutant cells. IMPLICATIONS: Our data support the hypothesis that inhibitors targeting the CoREST complex may be clinically effective in patients with colorectal cancer harboring PIK3CA mutations.

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

Abstract 903: Evaluation of predictive biomarkers and resistance mechanisms of PI3K pathway inhibition in head and neck squamous cell carcinoma

Abstract Head and neck Squamous cell carcinoma (HNSCC) is a lethal, disabling and disfiguring cancer with no biomarker-directed therapeutic options. We are in a desperate need for novel targeted therapies. PI3K/AKT/mTOR is one of the most often altered pathways in HNSCC. This pathway is important for cancer cell signaling and several pharmacological inhibitors are already in clinical trials for other cancer types. Our lab previously found that HNSCC cell lines with PIK3CA mutations were more sensitive to pathway inhibitors compared to other PI3K pathway alterations such as PIK3CA amplification or PTEN loss and that activation of ERK is one mechanism responsible for PI3K inhibitor resistance. In this report we extended our study to further investigate the predictive biomarkers, biological effects of PI3K inhibition, the potential pathways of resistance and the use of rational drug combination in a diverse panel of HNSCC cell lines. We tested 64 HNSCC cell lines with the PI3K inhibitor GDC0941 and correlated drug sensitivity with basal PI3K pathway activation, PI3K copy number or PIK3CA mutation. We confirmed that cell lines with PIK3CA mutations were more sensitive to GDC0941 (P= 6.35X 10 -13) and those with amplification were not. We tested another four PI3K pathway inhibitors, including one PI3K inhibitor GSK1059615, one dual PI3K/mTOR inhibitor GDC0980, one AKT inhibitor GDC690693 and one mTOR inhibitor AZD8055 in a panel of 18 cell lines and found that the trend of drug sensitivity was similar (P < 0.05) in two PI3K inhibitors and one dual inhibitor where as AKT and mTOR inhibitors had a distinct trend. We evaluated the basal activation of PI3K/AKT/mTOR pathway using reverse phase protein array (RPPA) with two proteomic scores: PI3K/AKT and TSC/mTOR. Neither score predicted sensitivity to GDC0941. We also analyzed the PI3K/AKT and TSC/mTOR scores in 200 HNSCC tumors from the TCGA . In the same way PIK3CA amplification did not correlate with the scores whereas the PI3K/AKT score was higher in the PIK3CA mutants (P < 0.039) compared to WT PIK3CA. The RPPA did identify several biomarkers, including VEGFR2, pCRAF and PCNA, whose expression correlated with GDC0941 sensitivity. Treatment with GDC0941 caused cell cycle arrest in sensitive cell lines, but not in resistant cell lines. To identify potential resistance pathways following GDC0941 treatment in resistant lines, we tested 39 phosphoproteins using phosphoscan analysis and found that EGFR, IGF-1R, RET, FGFR3, and M-CSFR were activated in resistant cell lines after incubation with GDC0941. Combination therapy with GDC0941 and the EGFR inhibitor erlotinib was synergistic in resistant cell lines. Our data will be useful to conduct biomarker-based clinical trials in HNSCC in the near future. Citation Format: Tuhina Mazumdar, Lauren A. Byers, Patrick Ng, Gordon B. Mills, Shaohua Peng, Lixia Diao, Youhong Fan, Katherine Stemke-Hale, John V. Heymach, Jeffrey N. Myers, Bonnie S. Glisson, Faye M. Johnson. Evaluation of predictive biomarkers and resistance mechanisms of PI3K pathway inhibition in head and neck squamous cell carcinoma. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 903. doi:10.1158/1538-7445.AM2014-903

Vemurafenib and panitumumab combination tailored therapy in BRAF-mutated metastatic colorectal cancer

As the knowledge on cancer genetic alterations progresses, it fosters the need for more personalized therapeutic intervention in modern cancer management. Recently, mutations in KRAS, BRAF, and PIK3CA genes have emerged as important mechanisms of resistance to EGFR-targeted therapy in metastatic colorectal cancer (mCRC). Here we report the first case of a mCRC patient whose disease had progressed on standard lines of treatment and for which we devised a personalized therapeutic approach consisting of vemurafenib (ZelborafTM) and panitumumab (VectibixTM), based on the following molecular profile: BRAFV600E-mutant, amplified EGFR (double positive) and WT KRAS, WT PIK3CA, not-amplified HER2 (triple negative). This new combination therapy was well tolerated and resulted in a strong control of the disease. In particular, the vemurafenib-panitumumab combination appears to limit the typical toxicity of single agents, since no cutaneous toxic effects typically associated with vemurafenib were observed. Here we report the first clinical evidence that the combination of an anti-EGFR (panitumumab) and an inhibitor of BRAFV600E (vemurafenib) is well tolerated and results in a strong disease control in an extensively pretreated mCRC patient.

Analysis of serum biomarkers and tumor genetic alterations from a phase II study of lenvatinib in patients with advanced BRAF wild-type melanoma.

9058 Background: Lenvatinib is an oral receptor tyrosine kinase inhibitor targeting VEGFR1-3, FGFR1-4, RET, KIT, and PDGFRβ. Phase I and II studies of lenvatinib demonstrate that a subset of advanced melanoma patients (pts) appears to derive benefit from lenvatinib treatment (tx), prompting a need to identify predictive biomarkers for response to lenvatinib. Methods: Serum and archival tumor samples were collected from 93 enrolled pts in the BRAF wild-type (wt) cohort of the lenvatinib phase II study of advanced melanoma. Concentrations of 50 factors were measured in pre- and post-tx serum samples; 58 archival tumor tissues were obtained and gene mutation (mut) (n=53) and gene expression profiling (GEP) (n=39) analyses were performed. For mut analysis, targeted resequencing was performed on a select panel of genes using the Ion PGM Sequencer and mut validation studies were performed. For GEP analysis, the nCounterAnalysis System was used to measure the expression level of 330 genes. Results: Clinical benefit rate (32%) and objective response rate (9%) by independent radiologic review were observed in the BRAF wt cohort. In serum biomarker analysis, lenvatinib tx resulted in a decrease in soluble VEGFR2 and increase in VEGF and PlGF levels consistent with target engagement. Correlation with clinical outcome demonstrated that baseline (BL) levels of Ang-2, IL8, PlGF, and PDGFBB associated with OS, but only pts with low BL Ang-2 levels also demonstrated improved response. High BL levels of FLT3LG and eotaxin associated with longer OS and improved response. In GEP analysis, expression levels of a set of genes including TARBP2, ZNF544, and NF1 (targets identified in phase I and preclinical studies) associated with OS. In gene mut analysis, NRAS mut showed a trend towards longer OS. Pts with NRAS mut along with wt PIK3CA status demonstrated longer OS. Conclusions: Lenvatinib demonstrated limited response in BRAF wt advanced melanoma pts. A subset of pts may derive extended clinical benefit. NRAS mut/PIK3CA wt status and low BL Ang-2 levels appear to associate with improved clinical outcome in this pt population and require further study to assess their predictive value. Clinical trial information: NCT01136967.

Use of wild-type (wt) KRAS, BRAF, and PIK3CA, combined with KRAS mutations (mut) in codon 13 and RNA expression level of amphiregulin (AREG) and epiregulin (EREG), to predict cetuximab (CE) response with high accuracy in colorectal cancer of all four Dukes' stages.

517 Background: wt KRAS and wt BRAF are established clinical markers to predict response to CE in patients (pts) with mCRC. Some pts with KRAS mut in codon 13 respond to CE, while the majority of them do not. Recently, it was shown that pts with CRC of Duke C and wt KRAS and wt BRAF do not benefit from CE added to FOLFOX (ASCO 2011 abstr 3607). In addition, data indicated that AREG and EREG RNA expression is also correlated with CE response. We established a panel of 133 xenograft models from primary tumor tissue of pts with CRC of all four Dukes stages and conducted a therapy experiment with CE (AACR '11, LB9086). Methods: mut status of KRAS (G12, G13, A146T); BRAF (V600E) and PIK3CA (E542K, E545K, H1047R) was assessed in all xenografts by allele-specific RT-PCR. KRAS codon 61 was sequenced. AREG and EREG expression levels were analyzed by RT-PCR expression assays. Results: We observed response to CE (treated to control ratio < 20%) in 18/67 (27%) of the treated xenografts. The distribution of responder (R) to non-responder (NR) is: Duke A: n=8; 2R / 6NR; B: n= 22; 8R / 14NR; C: n=28; 4R / 24 NR; D: n= 9; 4R / 5NR. Retrospective classification based on KRAS mut status identified R with a sensitivity (S+) of 83%, and NR with a specificity (S-) of 61%. If mut status in BRAF and PIK3CA were added the classifier showed S+ of 83% / S- of 78%. If any mut except in KRAS codon 13 were considered, the classifier reached S+ of 94% / S- of 69%. We improved S- of the classifiers to 86%; 90%, and 86%, respectively by adding AREG and EREG RNA expression data. The most accurate classifier combined wt KRAS, wt BRAF, wt PIK3CA with mut in codon 13 and RNA expression of AREG and EREG and reached S+ of 94% / S- of 86%. Classification in corresponding primary tumors showed similar accuracy. Conclusions: We developed a powerful classifier for all Dukes stages to predict response to CE with S+ of 94% and S- of 86%. In adjuvant setting the mut based classifier reaches S+ of 100% and S- of 68%; S- can be improved to 79% by adding AREG/EREG. This novel classifier has the potential to be used in the adjuvant and metastatic setting to improve pts selection for CE therapy.

PIK3CA mutations frequently coexist with RAS and BRAF mutations in patients with advanced cancers.

BackgroundOncogenic mutations of PIK3CA, RAS (KRAS, NRAS), and BRAF have been identified in various malignancies, and activate the PI3K/AKT/mTOR and RAS/RAF/MEK pathways, respectively. Both pathways are critical drivers of tumorigenesis.MethodsTumor tissues from 504 patients with diverse cancers referred to the Clinical Center for Targeted Therapy at MD Anderson Cancer Center starting in October 2008 were analyzed for PIK3CA, RAS (KRAS, NRAS), and BRAF mutations using polymerase chain reaction-based DNA sequencing.Results PIK3CA mutations were found in 54 (11%) of 504 patients tested; KRAS in 69 (19%) of 367; NRAS in 19 (8%) of 225; and BRAF in 31 (9%) of 361 patients. PIK3CA mutations were most frequent in squamous cervical (5/14, 36%), uterine (7/28, 25%), breast (6/29, 21%), and colorectal cancers (18/105, 17%); KRAS in pancreatic (5/9, 56%), colorectal (49/97, 51%), and uterine cancers (3/20, 15%); NRAS in melanoma (12/40, 30%), and uterine cancer (2/11, 18%); BRAF in melanoma (23/52, 44%), and colorectal cancer (5/88, 6%). Regardless of histology, KRAS mutations were found in 38% of patients with PIK3CA mutations compared to 16% of patients with wild-type (wt)PIK3CA (p = 0.001). In total, RAS (KRAS, NRAS) or BRAF mutations were found in 47% of patients with PIK3CA mutations vs. 24% of patients wtPIK3CA (p = 0.001). PIK3CA mutations were found in 28% of patients with KRAS mutations compared to 10% with wtKRAS (p = 0.001) and in 20% of patients with RAS (KRAS, NRAS) or BRAF mutations compared to 8% with wtRAS (KRAS, NRAS) or wtBRAF (p = 0.001).Conclusions PIK3CA, RAS (KRAS, NRAS), and BRAF mutations are frequent in diverse tumors. In a wide variety of tumors, PIK3CA mutations coexist with RAS (KRAS, NRAS) and BRAF mutations.

Mutations of the catalytic subunit a of PI3K (PIK3CA) in erlotinib-treated non-small cell lung cancer (NSCLC) patients (p) with epidermal growth factor receptor (EGFR) mutations.

7588 Background: Stage IV NSCLC p with EGFR mutations treated with erlotinib had a median progression-free survival (PFS) of 14 months (m) and median survival (MS) of 27 m in our experience. However, EGFR mutations can only imperfectly predict outcome. PIK3CA mutations occur in several tumors and have prognostic and therapeutic implications. We examined the presence and potential influence of PIK3CA mutations on outcome to erlotinib in NSCLC p with EGFR mutations. Methods: PIK3CA mutation status was assessed in pretreatment paraffin-embedded tumor samples from 118 advanced NSCLC p with EGFR mutations treated with erlotinib. E542K, E545K and H1047R mutations were screened by 5’-nuclease PCR (Taqman) assay and confirmed by standard PCR followed by sequencing. Results: PIK3CA mutations were detected in 6 of 118 patients (5.1%). 84% of p with PIK3CA mutations had adenocarcinomas vs 50% of p with wild-type (wt) PIK3CA (P=0.01). Response rate was 50% for p with mutations vs 70% for p with wt PIK3CA (P=0.03). There were no other differences between p with and without PIK3CA mutations. 2 of the 6 p with PIK3CA mutations had the uncommon L861Q mutation in exon 21 of EGFR. 1 of the 6 p had complete response; 2 had partial response; 3 had progressive disease. There was a non-significant trend towards shorter PFS for the 6 p with PIK3CA mutations (9 vs 16 m; P=0.59). MS was not reached for the 6 p with PIK3CA mutations, while it was 29 m for p with wt PIK3CA (P=0.09). Conclusions: PIK3CA mutations can be present in some EGFR-mutant NSCLC p, with lower response and a trend towards shorter PFS. Treatment with EGFR tyrosine kinase inhibitors plus PIK3CA inhibitors should be tested in this small subset of p with double mutations.