Alternative lengthening of telomeres and loss of ATRX are frequent events in pleomorphic and dedifferentiated liposarcomas.

Telomerase activation and alternative lengthening of telomeres are two major mechanisms of telomere length maintenance. Soft tissue sarcomas appear to use the alternative lengthening of telomeres more frequently. Loss of α-thalassemia/mental retardation syndrome X-linked (ATRX) or death domain-associated protein 6 (DAXX) expression has been implicated in the pathogenesis of alternative telomere lengthening in pancreatic endocrine neoplasm and glioma. The mechanism leading to the alternative lengthening of telomeres in liposarcoma remains unknown. Whereas alternative telomere lengthening was determined to be an indicator of poor prognosis in liposarcomas as a whole, its prognostic power has not been verified in any subtype of liposarcoma. In this study, we characterized the status of alternative telomere lengthening and expression of ATRX and DAXX in 111 liposarcomas (28 well-differentiated, 52 dedifferentiated, 20 myxoid or round cell, and 11 pleomorphic liposarcomas) by telomere fluorescence in situ hybridization and immunohistochemistry, respectively. Alternative lengthening of telomere was observed in 0% (0/16) of well-differentiated, 30% (14/46) of dedifferentiated, 5% (1/19) of myxoid or round cell, and 80% (8/10) of pleomorphic liposarcomas. Eighteen (16%) and one (1%) tumors were negative for ATRX and DAXX immunostaining, respectively. Remarkably, all cases with loss of either ATRX or DAXX expression had alternative lengthening of telomeres, and 83% (19/23) of tumors that had alternative lengthening of telomeres showed loss of either protein. The correlation between loss of either ATRX or DAXX and alternative telomere lengthening was 100% in dedifferentiated liposarcoma. The presence of alternative telomere lengthening in dedifferentiated liposarcoma suggested poor overall survival (hazard ratio=1.954, P=0.077) and was the most significant indicator of short progression-free survival (hazard ratio=3.119, P=0.003). In conclusion, we found that ATRX loss was the most likely mechanism of alternative telomere lengthening in liposarcoma and alternative telomere lengthening was a prognostic factor of poor outcome in dedifferentiated liposarcoma.

Novel dedifferentiated liposarcoma xenograft models reveal PTEN down-regulation as a malignant signature and response to PI3K pathway inhibition.

Liposarcoma is a type of soft tissue sarcoma that exhibits poor survival and a high recurrence rate. Treatment is generally limited to surgery and radiation, which emphasizes the need for better understanding of this disease. Because very few in vivo and in vitro models can reproducibly recapitulate the human disease, we generated several xenograft models from surgically resected human dedifferentiated liposarcoma. All xenografts recapitulated morphological and gene expression characteristics of the patient tumors after continuous in vivo passages. Importantly, xenograftability was directly correlated with disease-specific survival of liposarcoma patients. Thus, the ability for the tumor of a patient to engraft may help identify those patients who will benefit from more aggressive treatment regimens. Gene expression analyses highlighted the association between xenograftability and a unique gene expression signature, including down-regulated PTEN tumor-suppressor gene expression and a progenitor-like phenotype. When treated with the PI3K/AKT/mTOR pathway inhibitor rapamycin alone or in combination with the multikinase inhibitor sorafenib, all xenografts responded with increased lipid content and a more differentiated gene expression profile. These human xenograft models may facilitate liposarcoma research and accelerate the generation of readily translatable preclinical data that could ultimately influence patient care.

Aberrant AKT activation drives well-differentiated liposarcoma.

Well-differentiated liposarcoma (WDLPS), one of the most common human sarcomas, is poorly responsive to radiation and chemotherapy, and the lack of animal models suitable for experimental analysis has seriously impeded functional investigation of its pathobiology and development of effective targeted therapies. Here, we show that zebrafish expressing constitutively active Akt2 in mesenchymal progenitors develop WDLPS that closely resembles the human disease. Tumor incidence rates were 8% in p53 wild-type zebrafish, 6% in p53 heterozygotes, and 29% in p53-homozygous mutant zebrafish (P = 0.013), indicating that aberrant Akt activation collaborates with p53 mutation in WDLPS pathogenesis. Analysis of primary clinical specimens of WDLPS, and of the closely related dedifferentiated liposarcoma (DDLPS) subtype, revealed immunohistochemical evidence of AKT activation in 27% of cases. Western blot analysis of a panel of cell lines derived from patients with WDLPS or DDLPS revealed robust AKT phosphorylation in all cell lines examined, even when these cells were cultured in serum-free media. Moreover, BEZ235, a small molecule inhibitor of PI3K and mammalian target of rapamycin that effectively inhibits AKT activation in these cells, impaired viability at nanomolar concentrations. Our findings are unique in providing an animal model to decipher the molecular pathogenesis of WDLPS, and implicate AKT as a previously unexplored therapeutic target in this chemoresistant sarcoma.

Carboxypeptidase M: a biomarker for the discrimination of well-differentiated liposarcoma from lipoma.

The discrimination between well-differentiated liposarcomas/atypical lipomatous tumors and lipomas can be diagnostically challenging at the histological level. However, cytogenetic identification of ring and giant rod chromosomes supports the diagnosis of well-differentiated liposarcoma/atypical lipomatous tumor. These abnormal chromosomes are mainly composed of amplified genomic sequences derived from chromosome 12q13-15, and contain several genes, including MDM2, CDK4 (SAS), TSPAN31, HMGA2, and others. MDM2 is consistently amplified in well-differentiated liposarcomas/atypical lipomatous tumors, and up to 25% in other sarcomas. As part of a large genomic study of lipomatous neoplasms, we initially found CPM to be consistently amplified in well-differentiated liposarcomas/atypical lipomatous tumors. To further explore this initial finding, we investigated the copy number status of MDM2 and CPM by fluorescent in situ hybridization (FISH) on a series of 138 tumors and 17 normal tissues, including 32 well-differentiated liposarcoma/atypical lipomatous tumors, 63 lipomas, 11 pleomorphic lipomas, 2 lipoblastomas, 30 other tumors and 17 normal fat samples. All 32 well-differentiated liposarcoma/atypical lipomatous tumors showed amplification of MDM2 and CPM, usually >20 copies per cell. The other tumors lacked MDM2 and/or CPM amplification. Chromogenic in situ hybridization confirmed the above results on a subset of these tumors (n=27). These findings suggest that identification of CPM amplification could be used as an alternative diagnostic tool for the diagnosis of well-differentiated liposarcoma/atypical lipomatous tumors.

Sorafenib inhibits growth and mitogen-activated protein kinase signaling in malignant peripheral nerve sheath cells.

Malignant peripheral nerve sheath tumors (MPNST) are soft-tissue tumors with a very poor prognosis and largely resistant to chemotherapy. MPNSTs are characterized by activation of the Ras pathway by loss of tumor suppressor neurofibromatosis type 1. In view of this, MPNST may be susceptible to inhibition of the activated Ras/Raf/mitogen-activated protein kinase pathway by the B-Raf inhibitor sorafenib. MPNST (MPNST and ST8814) and dedifferentiated liposarcoma (LS141 and DDLS) human tumor cell lines were characterized for Ras activation and B-Raf expression. Tumor cells were treated with sorafenib and examined for growth inhibition, inhibition of phospho-MEK, phospho-ERK, cell cycle arrest, and changes in cyclin D1 and pRb expression. MPNSTs were sensitive to sorafenib at nanomolar concentrations. This appeared to be due to inhibition of phospho-MEK, phospho-ERK, suppression of cyclin D1, and hypophosphorylation of pRb at the CDK4-specific sites, resulting in a G(1) cell cycle arrest. These effects were not seen in the liposarcoma cells, which either did not express B-Raf or showed decreased Ras activation. Small interfering RNA-mediated depletion of B-Raf in MPNSTs also induced a G(1) cell cycle arrest in these cells, with a marked inhibition of cyclin D1 expression and Rb phosphorylation, whereas depletion of C-Raf did not affect either. With growth inhibition at the low nanomolar range, sorafenib, by inhibiting the mitogen-activated protein kinase pathway, may prove to be a novel therapy for patients with MPNST.

Evidence for alternative lengthening of telomeres in liposarcomas in the absence of ALT-associated PML bodies.

Immortalized and cancer cells maintain their telomeres by activation of a telomere maintenance mechanism (TMM). In approximately 85% of cancers telomerase is activated (TA) but in some tumours, in particular sarcomas, an alternative lengthening of telomeres (ALT) pathway is used. Liposarcomas are the most common soft-tissue sarcoma in adults and they activate ALT or telomerase with equal frequency, however no TMM has been identified in approximately 50% of liposarcomas. In our study, we have shown that instability at the minisatellite MS32, usually associated with ALT activation, aids the identification of liposarcomas that have recombination-like activity at telomeres in absence of ALT associated PML-bodies (APBs). Furthermore, using single molecule telomere analysis, we have detected complex telomere mutations directly in ALT positive liposarcomas and interestingly in some liposarcomas with an unknown TMM but high MS32 instability. We have shown by sequence analysis that some of these complex telomere mutations must arise by an inter-molecular recombination-like process rather than by deletion caused by t-loop excision or by unequal telomere-sister-chromatid-exchange (T-SCE), which is known to be elevated in ALT cell lines. Preliminary evidence also suggests that inter-molecular recombination events may be processed differently in liposarcomas with APBs compared to those without. In conclusion, we have shown for the first time, that some telomerase negative liposarcomas without APBs have other features associated with ALT, indicating that the incidence of ALT in these tumours has previously been under-estimated. This has major implications for the use of cancer treatments targeted at TMMs.

Biophysical and biochemical characterization of a liposarcoma-derived recombinant MnSOD protein acting as an anticancer agent.

A recombinant MnSOD (rMnSOD) synthesized by specific cDNA clones derived from a liposarcoma cell line was shown to have the same sequence as the wild-type MnSOD expressed in the human myeloid leukaemia cell line U937, except for the presence of the leader peptide at the N-terminus. These results were fully confirmed by the molecular mass of rMnSOD as evaluated by ES/MS analysis (26662.7 Da) and the nucleotide sequence of the MnSOD cDNA. The role of the leader peptide in rMnSOD was investigated using a fluorescent and/or (68)Gallium-labelled synthetic peptide. The labelled peptide permeated MCF-7 cells and uptake could be inhibited in the presence of an excess of oestrogen. In vivo it was taken up by the tumour, suggesting that the molecule can be used for both therapy and diagnosis. The in vitro and in vivo pharmacology tests confirmed that rMnSOD is only oncotoxic for tumour cells expressing oestrogen receptors. Pharmacokinetic studies in animals performed with (125)I- and (131)I-labelled proteins confirmed that, when administered systemically, rMnSOD selectively reached the tumour, where its presence was unambiguously demonstrated by scintigraphic and PET scans. PCR analysis revealed that Bax gene expression was increased and the Bcl2 gene was down regulated in MCF7 cells treated with rMnSOD, which suggests that the protein induces a pro-apoptotic mechanism.

Matrix metalloproteinase expression in high grade soft tissue sarcomas.

Soft tissue sarcomas comprise a heterogeneous group of mesenchymal tumors with varying biological behavior ranging from indolent tumors with no or minimal metastatic risk to aggressive and frequently metastasizing tumors. Among the more common aggressive adult soft tissue sarcomas are malignant fibrous histiocytoma, synovial sarcoma and liposarcoma. Matrix metalloproteinases are enzymes which perform a homeostatic role in mesenchymal tissue and function in both tumorigenesis and metastasis. The objectives of this study are to determine the presence and relative quantity of matrix metalloproteinases (MMPs) -1, -2, -8, -9, and -13; extracellular matrix metalloproteinase inducer (EMMPRIN); and tissue inhibitors of matrix metalloproteinases (TIMP)-1 and -2 in high grade soft tissue sarcoma tumor specimens using real-time PCR. The second objective is to determine if a relationship exists between quantity of EMMPRIN, MMPs, and TIMPs expressed in tumor tissue and disease-free survival. One hundred and forty patients diagnosed with high grade soft tissue sarcomas between 1995-2003 were identified. Tissue blocks and histologic slides were acquired for 41 specimens. Tumor specimens included 29 malignant fibrous histiocytomas, 3 liposarcomas and 11 synovial sarcomas. RNA was extracted and RT-PCR was performed in triplicate. No significant differences were found between the three types of high grade soft tissue sarcomas studied and the expression of MMPs. Interestingly, no relationship was found between high or low levels of MMPs when compared with disease-free survival. Our data support other research which finds variable correlation between MMP expression in soft tissue sarcomas and disease-free survival. We assert that the difference in correlation between MMP expression in carcinomas and sarcomas and disease-free survival is based on the vast phenotypic and genotypic difference between the cells of origin.

Inhibition of cell invasion and MMP production by a nutrient mixture in malignant liposarcoma cell line SW-872.

Liposarcoma, a malignancy of fat cells, is the most common soft tissue sarcoma. Though rare, poorly differentiated liposarcomas commonly metastasize to lungs and liver, leading to poor prognosis. Prevention of Extracellular matrix (ECM) degradation by inhibition of matrix metalloproteinases (MMPs) activity has been shown to be a promising therapeutic approach to inhibition of cancer progression. A nutrient mixture (NM) containing lysine, proline, ascorbic acid, and green tea extract has shown significant anticancer activity against a number of cancer cell lines. We investigated the effect of NM on liposarcoma cell line SW-872 proliferation (MTT assay), MMP secretion (gelatinase zymography), invasion through Matrigel, and apoptosis and morphology (live green caspase kit and H&E). Liposarcoma cell growth was inhibited by 36 and 61% at 500 and 1,000 microg/ml NM. Zymography demonstrated both MMP-2 and MMP-9 secretion, with PMA-enhanced MMP-9 activity. NM inhibited both MMPs with virtual total inhibition at 500 microg/ml NM. Invasion through Matrigel was inhibited at 100, 500, and 1,000 microg/ml by 44, 75, and 100%, respectively. Dose-dependent apoptosis of liposarcoma cells was evident with NM challenge, with virtually all cells exposed to 1,000 microg/ml NM in late apoptosis. H&E staining did not demonstrate any changes in morphology at lower concentrations. However, some apoptotic changes were evident at higher concentrations. In conclusion, NM significantly inhibited liposarcoma cell growth, MMP activity, and invasion and induced apoptosis in vitro-important parameters for cancer development, suggesting NM as a potential treatment strategy for liposarcoma.

MLN-8237: A dual inhibitor of aurora A and B in soft tissue sarcomas.

Aurora kinases have become an attractive target in cancer therapy due to their deregulated expression in human tumors. Liposarcoma, a type of soft tissue sarcoma in adults, account for approximately 20% of all adult soft tissue sarcomas. There are no effective chemotherapies for majority of these tumors. Efforts made to define the molecular basis of liposarcomas lead to the finding that besides the amplifications of CDK4 and MDM2, Aurora Kinase A, also was shown to be overexpressed. Based on these as well as mathematic modeling, we have carried out a successful preclinical study using CDK4 and IGF1R inhibitors in liposarcoma. MLN8237 has been shown to be a potent and selective inhibitor of Aurora A. MLN-8237, as per our results, induces a differential inhibition of Aurora A and B in a dose dependent manner. At a low nanomolar dose, cellular effects such as induction of phospho-Histone H3 (Ser10) mimicked as that of the inhibition of Aurora kinase A followed by apoptosis. However, micromolar dose of MLN-8237 induced polyploidy, a hallmark effect of Aurora B inhibition. The dose dependent selectivity of inhibition was further confirmed by using siRNA specific inhibition of Aurora A and B. This was further tested by time lapse microscopy of GFP-H2B labelled cells treated with MLN-8237. LS141 xenograft model at a dose of 30 mg/kg also showed efficient growth suppression by selective inhibition of Aurora Kinase A. Based on our data, a dose that can target only Aurora A will be more beneficial in tumor suppression.

C-kit expression in dedifferentiated and well-differentiated liposarcomas; immunohistochemistry and genetic analysis.

BACKGROUND: c-kit expression by immunohistochemistry has been utilized to identify cancer patients who can be treated with imatinib-mesylate. In gastrointestinal stromal tumors (GISTs), an activating mutation in c-kit predicts treatment response; its presence in other soft tissue tumors is unexplored. MATERIALS AND METHODS: We evaluated seven cases of dedifferentiated liposarcomas (DDLS) and compared those with seven well-differentiated liposarcomas (WDLS). Immunohistochemical staining for c-kit was performed using a polyclonal antibody. Using PCR, exons 9, 10-11, 12-13 and 17 of c-kit were amplified and direct DNA sequencing performed. RESULTS: Two out of 7 (30%) DDLS showed focal weak immunoreactivity with c-kit; no (0%) WDLS stained with c-kit. Seven out of 7 (100%) DDLS showed an allelic variation in exon 10, with a single base pair substitution (A >C) at codon 541; 3/7 (43%) WDLS showed the same change. CONCLUSION: c-kit immunoreactivity did not correlate with the change in DNA sequence; DDLS showed a consistent allelic variation in c-kit that may have significant prognostic, diagnostic and therapeutic implications.

Myxoid liposarcoma with transition to round-cell lesion-cell cycle regulator genes and telomerase activity characterizing tumor progression: a case report.

A mixed myxoid/round cell liposarcoma was macrodissected in its 2 histologic components and investigated for genetic differences between its low-grade myxoid and the high-grade round-cell region. For both, we failed to detect p53 gene mutations, loss of heterozygosity at the p53 or Rb genes, and p53 protein expression. The round-cell component showed a high telomerase activity, and an elevated c-myc mRNA and protein expression. The myxoid component was characterized by a lack of telomerase activity and low c-myc mRNA expression, and immunohistochemistry failed to detect the c-myc protein. There was a higher Mib-1 proliferation index in the round-cell portion. The same specific translocation t(12;16) and the fusion transcript type II in both components confirmed the close relationship between myxoid and round-cell liposarcomas. Telomerase activity and increased c-myc expression seem to be helpful molecular markers for characterizing tumor progression in myxoid liposarcoma.

Alterations of serum enzymes during therapy directed at human malignant sarcomas: a radiological follow-up study of tumor transformation.

1. When a malignant growth is developing in a patient, one often observes in the serum an increased activity of serum enzymes due to necrosis and increased membrane permeability caused by the altered metabolism of malignant cells. Conversely, I considered it interesting to check the enzymes of the malate-aspartate shuttle in addition to LDH enzyme when a neoplastic growth is regressing due to radiation therapy. The patients who were selected for this study had histologically proved sarcomas (reticulosarcoma, liposarcoma, and post-nosal sarcoma). 2. The data obtained indicated that tumor regression is heralded by progressive decline (to the normal level) of LDH, GOT and MDH activities in serum. Normalization of these systems suggested that reticulosarcoma, liposarcoma, and post-nosal sarcoma are sensitive to the therapeutic agent used. 3. In viewing the data herein reported a definitive conclusion regarding the diagnostic usefulness of these assays is apparent. It seems possible that the measurement of these enzymes in serum of patients with proved sarcomas, may prove to be useful laboratory adjunct to diagnostic radiology and in the management of patients whose diagnosis has already been established.

Activation of metalloproteinases-2 and -9 by interleukin-1alpha in S100A4-positive liposarcoma cell line: correlation with cell invasiveness.

BACKGROUND: The S100A4 gene may affect the invasive properties of tumor cells through modulation of metalloproteinases (MMPs) and their inhibitors (TIMPs). MATERIALS AND METHODS: In the human liposarcoma cell line, SW872, we analyzed the expression of S100A4 protein by immunohistochemistry and flow cytometry. The production of MMP2, MMP9, TIMP1 and TIMP2 was assessed by gelatin zymography and enzyme-linked immunoabsorbent assay before and after interleukin-1alpha (IL-1alpha) and interleukin-6 (IL-6) stimulation; cell invasiveness was measured by Matrigel invasion assay. RESULTS: S100A4-positive SW872 cells responded to IL-1alpha with induction of immunoreactive MMP2 and TIMP1 and with activation of both MMPs, the latter significantly associated with an increase of cell invasiveness. Treatment with IL-6 induced less significant variations resulting in a more stable invasive behavior. CONCLUSION: These data show that S100A4-positive SW872 respond to interleukins by influencing the behavior of factors involved in extracellular matrix degradation and emphasize the predominant role of MMP activity status on the positive regulation of cell migration mechanisms.

Antitumor chemosensitivity differs between clinical sarcoma and adenocarcinoma tissues.

The chemosensitivity of 43 human sarcoma tissues, including 18 osteosarcomas, 16 leiomyosarcomas and 9 liposarcomas, was compared with that of 28 adenocarcinomas of the stomach, using the in vitro succinate dehydrogenase inhibition (SDI) test. These tissues were exposed for 3 days to each antitumor drug, including adriamycin (ADM), 5-fluorouracil (5-FU), mitomycin C (MMC), cisplatin (CDDP), aclacinomycin A (ACR) and carboquone (CQ), them the cell viability was estimated based on the succinate dehydrogenase (SD) activity, determined using [3-(4,5-dimethyl-2-thiazolyl) -2,5-diphenyl-2H tetrazolium bromide] (MTT). SD activity was significantly lower in the osteosarcoma as compared to that in the adenocarcinoma, for ADM, MMC, CDDP, ACR and CQ (p < 0.01), and was higher for ADM (p < 0.05) in cases of leiomyosarcoma and for CDDP (p < 0.01) and ACR (p < 0.05) in cases of liposarcoma. The sensitivity rate was higher in osteosarcoma than in adenocarcinoma for ADM, MMC and CDDP. These findings suggest that patients with osteosarcoma will probably show a fairly good response to antitumor drugs, and that when liposarcoma or leiomyosarcoma tumors show resistance to antitumor drugs, then resection at the time of initial exploration and combined modalities, including radiation and hyperthermia, should be considered.

Expression of telomerase activity and telomerase RNA in human soft tissue sarcomas.

OBJECTIVE: To investigate whether telomerase is reactivated in soft tissue tumor and whether telomerase activity is regulated at the transcriptional level. DESIGN: Fresh tissue samples of 24 soft tissue sarcomas were analyzed for telomerase activity by a radioactive polymerase chain reaction-based telomeric repeat amplification protocol assay and for human telomerase RNA (hTR) by an in situ hybridization assay. SETTING: Tertiary care teaching hospital. PATIENTS: Twenty-four patients with soft tissue tumor were surgically treated. Twelve patients had malignant fibrous histiocytoma, 5 had liposarcoma, 6 had leiomyosarcoma, and 1 had rhabdomyosarcoma. RESULTS: Telomerase activity was detected in 4 sarcoma samples (17%), all of which were positive for hTR. Expression of hTR was demonstrated in 13 sarcomas (54%), 4 of which were positive for telomerase and 9 of which were negative for telomerase. One (50%) of 2 grade 1 tumors, 9 (50%) of 18 grade 2 tumors, and 3 (75%) of 4 grade 3 tumors showed hTR expression. CONCLUSIONS: The relatively low frequency of telomerase activity in soft tissue sarcomas suggests that telomerase may not play an important role in tumorigenesis in these tumors. Telomerase ladders were demonstrated only in association with tumors expressing hTR. It is noteworthy that half of the patients with grade 1 and 2 tumors expressed hTR, suggesting that telomerase RNA may be useful as a marker for identifying tumor aggressiveness earlier than the conventional histopathologic grading scale.

Cyclin-dependent kinase 11 (CDK11) is crucial in the growth of liposarcoma cells.

Liposarcoma is the second most common soft tissue sarcoma in adults, but treatment options have been quite limited thus far. In this study, we investigated the functional and therapeutic relevance of cyclin-dependent kinase 11 (CDK11) as a putative target in liposarcoma. CDK11 knockdown by synthetic siRNA or lentiviral shRNA decreased cell proliferation, and induced apoptosis in liposarcoma cells. Moreover, CDK11 knockdown enhances the cytotoxic effect of doxorubicin to inhibit cell growth in liposarcoma cells. These findings suggest that CDK11 is critical for the growth and proliferation of liposarcoma cells. CDK11 may be a promising therapeutic target for the treatment of liposarcoma patients.

Drug synergy screen and network modeling in dedifferentiated liposarcoma identifies CDK4 and IGF1R as synergistic drug targets.

Dedifferentiated liposarcoma (DDLS) is a rare but aggressive cancer with high recurrence and low response rates to targeted therapies. Increasing treatment efficacy may require combinations of targeted agents that counteract the effects of multiple abnormalities. To identify a possible multicomponent therapy, we performed a combinatorial drug screen in a DDLS-derived cell line and identified cyclin-dependent kinase 4 (CDK4) and insulin-like growth factor 1 receptor (IGF1R) as synergistic drug targets. We measured the phosphorylation of multiple proteins and cell viability in response to systematic drug combinations and derived computational models of the signaling network. These models predict that the observed synergy in reducing cell viability with CDK4 and IGF1R inhibitors depends on the activity of the AKT pathway. Experiments confirmed that combined inhibition of CDK4 and IGF1R cooperatively suppresses the activation of proteins within the AKT pathway. Consistent with these findings, synergistic reductions in cell viability were also found when combining CDK4 inhibition with inhibition of either AKT or epidermal growth factor receptor (EGFR), another receptor similar to IGF1R that activates AKT. Thus, network models derived from context-specific proteomic measurements of systematically perturbed cancer cells may reveal cancer-specific signaling mechanisms and aid in the design of effective combination therapies.

Carboxypeptidase M in apoptosis, adipogenesis and cancer.

This review covers carboxypeptidase M (CPM) research that appeared in the literature since 2009. The focus is on aspects that are new or interesting from a clinical perspective. Available research tools are discussed as well as their pitfalls and limitations. Evidence is provided to suggest the potential involvement of CPM in apoptosis, adipogenesis and cancer. This evidence derives from the expression pattern of CPM and its putative substrates in cells and tissues. In recent years CPM emerged as a potential cancer biomarker, in well differentiated liposarcoma where the CPM gene is co-amplified with the oncogene MDM2; and in lung adenocarcinoma where coexpression with EGFR correlates with poor prognosis. The available data call for extended investigation of the function of CPM in tumor cells, tumor-associated macrophages, stromal cells and tumor neovascularisation. Such experiments could be instrumental to validate CPM as a therapeutic target.