Simona Lamba

Bio: Simona Lamba is an academic researcher from University of Turin. The author has contributed to research in topics: KRAS & Colorectal cancer. The author has an hindex of 26, co-authored 46 publications receiving 4583 citations.

Clonal evolution and resistance to EGFR blockade in the blood of colorectal cancer patients

Abstract: By monitoring ctDNA, the authors reveal the dynamic adaption of clonal populations in colorectal cancer patients treated with anti-EGFR therapy, suggesting that therapeutic re-challenge may have some benefit.

Association of KRAS p.G13D Mutation With Outcome in Patients With Chemotherapy-Refractory Metastatic Colorectal Cancer Treated With Cetuximab

Abstract: Context Patients with metastatic colorectal cancer who have KRAS codon 12- or KRAS codon 13-mutated tumors are presently excluded from treatment with the anti-epidermal growth factor receptor monoclonal antibody cetuximab. Objective To test the hypothesis that KRAS codon 13 mutations are associated with a better outcome after treatment with cetuximab than observed with other KRAS mutations. Design, Setting, and Patients We studied the association between KRAS mutation status (p.G13D vs other KRAS mutations) and response and survival in a pooled data set of 579 patients with chemotherapy-refractory colorectal cancer treated with cetuximab between 2001 and 2008. Patients were included in the CO. 17, BOND, MABEL, EMR202600, EVEREST, BABEL, or SALVAGE clinical trials or received off-study treatment. Univariate and multivariate analyses, adjusting for possible prognostic factors and data set, were performed. The effect of the different mutations was studied in vitro by constructing isogenic cell lines with wild-type KRAS, p.G12V, or p.G13D mutant alleles and treating them with cetuximab. Main Outcome Measures The main efficacy end point was overall survival. Secondary efficacy end points were response rate and progression-free survival. Results In comparison with patients with other KRAS-mutated tumors, patients with p.G13D-mutated tumors (n=32) treated with cetuximab had longer overall survival (median, 7.6 [95% confidence interval {CI}, 5.7-20.5] months vs 5.7 [95% CI, 4.9-6.8] months; adjusted hazard ratio [HR], 0.50; 95% CI, 0.31-0.81; P=.005) and longer progression-free survival (median, 4.0 [95% CI, 1.9-6.2] months vs 1.9 [95% CI, 1.8-2.8] months; adjusted HR, 0.51; 95% CI, 0.32-0.81; P=.004). There was a significant interaction between KRAS mutation status (p.G13D vs other KRAS mutations) and overall survival benefit with cetuximab treatment (adjusted HR, 0.30; 95% CI, 0.14-0.67; P=.003). In vitro and mouse model analysis showed that although p.G12V-mutated colorectal cells were insensitive to cetuximab, p.G13D-mutated cells were sensitive, as were KRAS wild-type cells. Conclusions In this analysis, use of cetuximab was associated with longer overall and progression-free survival among patients with chemotherapy-refractory colorectal cancer with p.G13D-mutated tumors than with other KRAS-mutated tumors. Evaluation of cetuximab therapy in these tumors in prospective randomized trials may be warranted. JAMA. 2010; 304(16): 1812-1820

Inactivation of DNA repair triggers neoantigen generation and impairs tumour growth

Abstract: Molecular alterations in genes involved in DNA mismatch repair (MMR) promote cancer initiation and foster tumour progression. Cancers deficient in MMR frequently show favourable prognosis and indolent progression. The functional basis of the clinical outcome of patients with tumours that are deficient in MMR is not clear. Here we genetically inactivate MutL homologue 1 (MLH1) in colorectal, breast and pancreatic mouse cancer cells. The growth of MMR-deficient cells was comparable to their proficient counterparts in vitro and on transplantation in immunocompromised mice. By contrast, MMR-deficient cancer cells grew poorly when transplanted in syngeneic mice. The inactivation of MMR increased the mutational burden and led to dynamic mutational profiles, which resulted in the persistent renewal of neoantigens in vitro and in vivo, whereas MMR-proficient cells exhibited stable mutational load and neoantigen profiles over time. Immune surveillance improved when cancer cells, in which MLH1 had been inactivated, accumulated neoantigens for several generations. When restricted to a clonal population, the dynamic generation of neoantigens driven by MMR further increased immune surveillance. Inactivation of MMR, driven by acquired resistance to the clinical agent temozolomide, increased mutational load, promoted continuous renewal of neoantigens in human colorectal cancers and triggered immune surveillance in mouse models. These results suggest that targeting DNA repair processes can increase the burden of neoantigens in tumour cells; this has the potential to be exploited in therapeutic approaches.

IDH1 mutations at residue p.R132 (IDH1(R132)) occur frequently in high-grade gliomas but not in other solid tumors.

Abstract: Systematic sequence profiling of the Glioblastoma Multiforme (GBM) genome has recently led to the identification of somatic mutations in the isocitrate dehydrogenase 1 (IDH1) gene. Interestingly, only the evolutionarily conserved residue R132 located in the substrate binding site of IDH1 was found mutated in GBM. At present, the occurrence and the relevance of p.R132 (IDH1R132) variants in tumors other than GBMs is largely unknown. We searched for mutations at position R132 of the IDH1 gene in a panel of 672 tumor samples. These included high-grade glioma, gastrointestinal stromal tumors (GIST), melanoma, bladder, breast, colorectal, lung, ovarian, pancreas, prostate, and thyroid carcinoma specimens. In addition, we assessed a panel of 84 cell lines from different tumor lineages. Somatic mutations affecting the IDH1R132 residue were detected in 20% (23 of 113) high-grade glioma samples. In addition to the previously reported p.R132H and p.R132S alleles, we identified three novel somatic mutations (p.R132C, p.R132G, and p.R132L) affecting residue IDH1R132 in GBM. Strikingly, no IDH1 mutations were detected in the other tumor types. These data indicate that cancer mutations affecting IDH1R132 are tissue-specific, and suggest that it plays a unique role in the development of high-grade gliomas. Hum Mutat 30, 7–11, 2009. © 2008 Wiley-Liss, Inc.

The prognostic IDH1 R132 mutation is associated with reduced NADP + -dependent IDH activity in glioblastoma

Abstract: Somatic mutations in the isocitrate dehydrogenase 1 gene (IDH1) occur at high frequency in gliomas and seem to be a prognostic factor for survival in glioblastoma patients. In our set of 98 glioblastoma patients, IDH1 ( R132 ) mutations were associated with improved survival of 1 year on average, after correcting for age and other variables with Cox proportional hazards models. Patients with IDH1 mutations were on average 17 years younger than patients without mutation. Mutated IDH1 has a gain of function to produce 2-hydroxyglutarate by NADPH-dependent reduction of alpha-ketoglutarate, but it is unknown whether NADPH production in gliomas is affected by IDH1 mutations. We assessed the effect of IDH1 (R132 ) mutations on IDH-mediated NADPH production in glioblastomas in situ. Metabolic mapping and image analysis was applied to 51 glioblastoma samples of which 16 carried an IDH1 (R132 ) mutation. NADP+-dependent IDH activity was determined in comparison with activity of NAD+-dependent IDH and all other NADPH-producing dehydrogenases, glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, malate dehydrogenase, and hexose-6-phosphate dehydrogenase. The occurrence of IDH1 mutations correlated with approx. twofold diminished NADP+-dependent IDH activity, whereas activity of NAD+-dependent IDH and the other NADP+-dependent dehydrogenases was not affected in situ in glioblastoma. The total NADPH production capacity in glioblastoma was provided for 65% by IDH activity and the occurrence of IDH1 (R132 ) mutation reduced this capacity by 38%. It is concluded that NADPH production is hampered in glioblastoma with IDH1 (R132 ) mutation. Moreover, mutated IDH1 consumes rather than produces NADPH, thus likely lowering NADPH levels even further. The low NADPH levels may sensitize glioblastoma to irradiation and chemotherapy, thus explaining the prolonged survival of patients with mutated glioblastoma.

Understanding the Warburg Effect: The Metabolic Requirements of Cell Proliferation

Abstract: In contrast to normal differentiated cells, which rely primarily on mitochondrial oxidative phosphorylation to generate the energy needed for cellular processes, most cancer cells instead rely on aerobic glycolysis, a phenomenon termed “the Warburg effect.” Aerobic glycolysis is an inefficient way to generate adenosine 5′-triphosphate (ATP), however, and the advantage it confers to cancer cells has been unclear. Here we propose that the metabolism of cancer cells, and indeed all proliferating cells, is adapted to facilitate the uptake and incorporation of nutrients into the biomass (e.g., nucleotides, amino acids, and lipids) needed to produce a new cell. Supporting this idea are recent studies showing that (i) several signaling pathways implicated in cell proliferation also regulate metabolic pathways that incorporate nutrients into biomass; and that (ii) certain cancer-associated mutations enable cancer cells to acquire and metabolize nutrients in a manner conducive to proliferation rather than efficient ATP production. A better understanding of the mechanistic links between cellular metabolism and growth control may ultimately lead to better treatments for human cancer.

IDH1 and IDH2 Mutations in Gliomas

Abstract: Background A recent genomewide mutational analysis of glioblastomas (World Health Organization [WHO] grade IV glioma) revealed somatic mutations of the isocitrate dehydrogenase 1 gene (IDH1) in a fraction of such tumors, most frequently in tumors that were known to have evolved from lower-grade gliomas (secondary glioblastomas). Methods We determined the sequence of the IDH1 gene and the related IDH2 gene in 445 central nervous system (CNS) tumors and 494 non-CNS tumors. The enzymatic activity of the proteins that were produced from normal and mutant IDH1 and IDH2 genes was determined in cultured glioma cells that were transfected with these genes. Results We identified mutations that affected amino acid 132 of IDH1 in more than 70% of WHO grade II and III astrocytomas and oligodendrogliomas and in glioblastomas that developed from these lower-grade lesions. Tumors without mutations in IDH1 often had mutations affecting the analogous amino acid (R172) of the IDH2 gene. Tumors with IDH1 or IDH2 mutations h...

Regulation of cancer cell metabolism

Abstract: Interest in the topic of tumour metabolism has waxed and waned over the past century of cancer research. The early observations of Warburg and his contemporaries established that there are fundamental differences in the central metabolic pathways operating in malignant tissue. However, the initial hypotheses that were based on these observations proved inadequate to explain tumorigenesis, and the oncogene revolution pushed tumour metabolism to the margins of cancer research. In recent years, interest has been renewed as it has become clear that many of the signalling pathways that are affected by genetic mutations and the tumour microenvironment have a profound effect on core metabolism, making this topic once again one of the most intense areas of research in cancer biology.

Detection of Circulating Tumor DNA in Early- and Late-Stage Human Malignancies

Abstract: The development of noninvasive methods to detect and monitor tumors continues to be a major challenge in oncology. We used digital polymerase chain reaction-based technologies to evaluate the ability of circulating tumor DNA (ctDNA) to detect tumors in 640 patients with various cancer types. We found that ctDNA was detectable in >75% of patients with advanced pancreatic, ovarian, colorectal, bladder, gastroesophageal, breast, melanoma, hepatocellular, and head and neck cancers, but in less than 50% of primary brain, renal, prostate, or thyroid cancers. In patients with localized tumors, ctDNA was detected in 73, 57, 48, and 50% of patients with colorectal cancer, gastroesophageal cancer, pancreatic cancer, and breast adenocarcinoma, respectively. ctDNA was often present in patients without detectable circulating tumor cells, suggesting that these two biomarkers are distinct entities. In a separate panel of 206 patients with metastatic colorectal cancers, we showed that the sensitivity of ctDNA for detection of clinically relevant KRAS gene mutations was 87.2% and its specificity was 99.2%. Finally, we assessed whether ctDNA could provide clues into the mechanisms underlying resistance to epidermal growth factor receptor blockade in 24 patients who objectively responded to therapy but subsequently relapsed. Twenty-three (96%) of these patients developed one or more mutations in genes involved in the mitogen-activated protein kinase pathway. Together, these data suggest that ctDNA is a broadly applicable, sensitive, and specific biomarker that can be used for a variety of clinical and research purposes in patients with multiple different types of cancer.

Cancer-associated IDH1 mutations produce 2-hydroxyglutarate

Abstract: Mutations in the enzyme cytosolic isocitrate dehydrogenase 1 (IDH1) are a common feature of a major subset of primary human brain cancers. These mutations occur at a single amino acid residue of the IDH1 active site, resulting in loss of the enzyme's ability to catalyse conversion of isocitrate to alpha-ketoglutarate. However, only a single copy of the gene is mutated in tumours, raising the possibility that the mutations do not result in a simple loss of function. Here we show that cancer-associated IDH1 mutations result in a new ability of the enzyme to catalyse the NADPH-dependent reduction of alpha-ketoglutarate to R(-)-2-hydroxyglutarate (2HG). Structural studies demonstrate that when arginine 132 is mutated to histidine, residues in the active site are shifted to produce structural changes consistent with reduced oxidative decarboxylation of isocitrate and acquisition of the ability to convert alpha-ketoglutarate to 2HG. Excess accumulation of 2HG has been shown to lead to an elevated risk of malignant brain tumours in patients with inborn errors of 2HG metabolism. Similarly, in human malignant gliomas harbouring IDH1 mutations, we find markedly elevated levels of 2HG. These data demonstrate that the IDH1 mutations result in production of the onco-metabolite 2HG, and indicate that the excess 2HG which accumulates in vivo contributes to the formation and malignant progression of gliomas.