• Asian Pacific Journal of Cancer Prevention
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• v.13 no.12
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• pp.6155-6157
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• 2012

Background: Mutations in the MAPK (Mitogen Activated Protein Kinase) signaling pathway - EGFR/Ras/RAF/MEK have been associated with the development of several carcinomas. ERK2, a downstream target of the MAPK pathway and a founding member of the MAPK family is activated by cellular signals emanating at the cell membrane. Activated ERK2 translocates into the nucleus to transactivate genes that promote cell proliferation. MKP - a dual specific phosphatase - interacts with activated ERK2 via the common docking (CD) domain of the later to inactivate (dephosphorylate) and effectively terminate further cell proliferation. A constitutively active form of ERK2 carrying a single point mutation - E322K in its CD domain, was earlier reported by our laboratory. In the present study, we investigated the prevalence of this CD domain E322K mutation in 88 well differentiated OSCC tissue samples. Materials and Method: Genomic DNA specimens isolated from 88 oral squamous cell carcinoma tissue samples were amplified with primers flanking the CD domain of the ERK2 gene. Subsequently, PCR amplicons were gel purified and subjected to direct sequencing to screen for mutations. Results: Direct sequencing of eighty eight OSCC samples identified an E322K CD domain mutation in only one (1.1%) OSCC sample. Conclusions: Our result indicates that mutation in the CD domain of ERK2 is rare in OSCC patients, which suggests the role of genetic alterations in other mitogenic genes in the development of carcinoma in the rest of the patients. Nevertheless, the finding is clinically significant, as the relatively rare prevalence of the E322K mutation in OSCC suggests that ERK2, being a common end point signal in the multi-hierarchical mitogen activated signaling pathway may be explored as a viable drug target in the treatment of OSCC.

• Proceedings of the Korean Society of Applied Pharmacology
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• 1996.11a
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• pp.135-139
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• 1996

$p70^{s6k}$ lies on a $p21^{ras}$-independent signalling pathway and plays an important role in mitogenesis. Activation is associated with phosphorylation at multiple sites, four of which lie in an autoinhibitory region. The immunosuppressant rapamycin induces $p70^{s6k}$ inactivation through dephosphorylation of a second set of mitogen-induced sites. Here we identify these sites as $T_{229}$, $T_{389}$, and $S_{404}$. $T_{229}$ resides in the "T loop" of the catalytic domain, an essential phosphorylation site in other kinases. However, $p70^{s6k}$ inactivation by rapamycin most closely parallels $T_{389}$ dephosphorylation. Mutation of $T_{389}$ to alanine ablates kinase activity, whereas mutation to glutamic acid confers constitutive kinase activity and rapamycin resistance. indicating an essential role for phosphorylation at this site. $T_{389}$ resides in an unusual hydrophobic motif, not previously noted, between the catalytic and autoinhibitory domains. The importance of this site, and surrounding motif, is emphasized by its conservation in other kinases including homologues of $p70^{s6k}$ derived from such distantly related organisms as yeast and plant.

• Molecules and Cells
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• v.43 no.2
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• pp.153-159
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• 2020

Neurofibromatosis type 1 (NF1) is an autosomal dominant disorder. NF1 patients are predisposed to formation of several type solid tumors as well as to juvenile myelomonocytic leukemia. Loss of NF1 results in dysregulation of MAPK, PI3K and other signaling cascades, to promote cell proliferation and to inhibit cell apoptosis. The RUNX1 gene is associated with stem cell function in many tissues, and plays a key role in the fate of stem cells. Aberrant RUNX1 expression leads to context-dependent tumor development, in which RUNX1 may serve as a tumor suppressor or an oncogene in specific tissue contexts. The co-occurrence of mutation of NF1 and RUNX1 is detected rarely in several cancers and signaling downstream of RAS-MAPK can alter RUNX1 function. Whether aberrant RUNX1 expression contributes to NF1-related tumorigenesis is not fully understood. This review focuses on the role of RUNX1 in NF1-related tumors and blood disorders, and in sporadic cancers.

• Asian Pacific Journal of Cancer Prevention
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• v.13 no.11
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• pp.5599-5603
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• 2012

Background: The epidermal growth factor receptor (EGFR) is a potential therapeutic target for breast cancer treatment; however, its use does not lead to a marked clinical response. Studies of non-small cell lung cancer and colorectal cancer showed that mutations of genes in the PIK3CA/AKT and RAS/RAF/MEK pathways, two major signalling cascades downstream of EGFR, might predict resistance to EGFR-targeted agents. Therefore, we examined the frequencies of mutations in these key EGFR pathway genes in Chinese breast cancer patients. Methods: We used a high-throughput mass-spectrometric based cancer gene mutation profiling platform to detect 22 mutations of the PIK3CA, AKT1, BRAF, EGFR, HRAS, and KRAS genes in 120 Chinese women with breast cancer. Results: Thirteen mutations were detected in 12 (10%) of the samples, all of which were invasive ductal carcinomas (two stage I, six stage II, three stage III, and one stage IV). These included one mutation (0.83%) in the EGFR gene (rs121913445-rs121913432), three (2.50%) in the KRAS gene (rs121913530, rs112445441), and nine (7.50%) in the PIK3CA gene (rs121913273, rs104886003, and rs121913279). No mutations were found in the AKT1, BRAF, and HRAS genes. Six (27.27%) of the 22 genotyping assays called mutations in at least one sample and three (50%) of the six assays queried were found to be mutated more than once. Conclusions: Mutations in the EGFR pathway occurred in a small fraction of Chinese breast cancers. However, therapeutics targeting these potential predictive markers should be investigated in depth, especially in Oriental populations.

• Development and Reproduction
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• v.20 no.1
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• pp.1-10
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• 2016

Molecular targeting for the altered signaling pathways has been proven to be effective for the treatment of many types of human cancer, including colorectal cancer (CRC). The dual phosphatidylinositol-3-kinase (PI3K) and mammalian target of rapamycin (mTOR) inhibitor BEZ235 has shown to exhibit potent antitumor activity against solid tumors. Autophagy is a cellular lysosomal catabolic process to maintain metabolic homeostasis, which has been known to be induced in response to many therapeutic agents in cancer cells. This process is negatively regulated by mTOR and often acts as prosurvival or prodeath mechanism following cancer therapeutics. The current study was designed to investigate the antiproliferation activity of BEZ235 and to evaluate the role of autophagy induced by BEZ235 using HCT15 CRC cells bearing ras oncogene mutation. We found that BEZ235 decreases cell viability, which was mostly dependent on $G_1$ arrest of cell cycle via suppression of cyclin A expression. BEZ235 affects PI3K/Akt/mTOR signaling pathway by increasing the phosphorylation of AKT at $Ser^{473}$ and RAS/RAF/MEK/ERK pathway by decreasing the phosphorylation of ERK at $Tyr^{204}$. BEZ235 also stimulated autophagy induction as evidenced by the increased expression of LC3-II and abundant acidic vesicular organelles (AVOs) in the cytoplasm. In addition, the combination of BEZ235 with autophagy inhibitor chloroquine, a known antagonist of autophagy, counteracted the antiproliferation effect of BEZ235. Thus, our study indicates that autophagy induced in response to BEZ235 treatment appears to act as cell death mechanism in HCT15 CRC cells.

• Journal of Applied Biological Chemistry
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• v.50 no.3
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• pp.109-114
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• 2007

Sar1p is a ras-related GTP-binding protein that functions in intracellular protein transport between the endoplasmic reticulum (ER) and the Golgi complex. The effector domain of Ras family proteins is highly conserved and this domain is functionally interchangeable in plant, yeast and mammalian Sar1. Using a recombinant Brassica sar1 protein (Bsar1p) harboring point mutations in its effector domain, we here investigated the ability of Sar1p to bind and hydrolyze GTP and to interact with the two sar1-specific regulators, GTPase activating protein (GAP) and guanine exchange factor (GEF). The T51A and T55A mutations impaired Bsar1p intrinsic GTP-binding and GDP-dissociation activity. In contrast, mutations in the switch domain of Bsar1 did not affect its intrinsic GTPase activity. Moreover, the P50A, P54A, and S56A mutations affected the interaction between Bsar1p and GAP. P54A mutant protein did not interact with two regulating proteins, GEF and GAP, even though the mutation didn't affect the intrinsic GTP-binding, nucleotide exchange or GTPase activity of Bsar1p.

• Journal of Genetic Medicine
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• v.6 no.1
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• pp.87-90
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• 2009

Cardiofaciocutaneous (CFC) syndrome is characterized by dysmorphic features, cardiac anomalies, and cutaneous abnormalities. CFC syndrome belongs to the class of Noonan-related diseases. CFC syndrome can be clinically differentiated from other Noonan-related diseases by the distinct craniofacial features of sparse hair, a hypoplastic supraorbital ridge, exophthalmos and nystagmus, and skin manifestations such as ichthyosis and hyperkeratosis. However, phenotypes can overlap among Noonan-related syndromes, including CFC syndrome. Recently, several genes in the RAS-MAPK pathway have been identified as disease-causing genes for Noonan-related diseases. Here, we report on a Korean girl diagnosed with CFC syndrome caused by a V-raf murine sarcoma viral oncogene homolog B1 (BRAF) gene mutation, and we discuss the phenotype-genotype heterogeneities in Noonan syndrome and Noonan-related diseases.

• Asian Pacific Journal of Cancer Prevention
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• v.16 no.2
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• pp.699-705
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• 2015

Vemurafenib has recently been used as drug for treatment of melanomas with $BRAF^{V600E}$ mutation. Unfortunately, treatment with only vemurafenib has not been sufficiently effective, with recurrence after a short period. In this study, three vemurafenib-resistant $BRAF^{V600E}$ melanoma cell lines, $A375P^R$, $A375M^R$ and SKMEL-$28^R$, were established from the original A375P, A375M and SKMEL-28 cell lines. Examination of the molecular mechanisms showed that the phosphorylation levels of MEK and ERK, which play key roles in the RAS/RAF/MEK/ERK signaling pathway, were reduced in these three cell lines, with increased phosphorylation levels of pAKTs limited to SKMEL-$28^R$ cells. Treatment of SKMEL-$28^R$ cells with 100 nM paclitaxel resulted in increased apoptosis and decreased cellular proliferation, invasion and colony formation via reduction of expression levels of EGFR and pAKTs. Moreover, vemurafenib-induced pAKTs in SKMEL-$28^R$ were decreased by treatment with an AKT inhibitor, MK-2206. Taken together, our results revealed that resistance mechanisms of $BRAF^{V600E}$-mutation melanoma cells to vemurafenib depended on the cell type. Our results suggested that paclitaxel should be considered as a drug in combination with vemurafenib to treat melanoma cells.

• Neonatal Medicine
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• v.25 no.3
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• pp.126-130
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• 2018

Parkes Weber syndrome is a rare congenital vascular anomaly, related to the RAS p21 protein activator 1 (RASA1) gene. It is characterized by capillary cutaneous malformations, bony and soft tissue hyperplasia, and multiple arteriovenous fistulas throughout the affected upper or lower extremity. These arteriovenous fistulas can be associated with life-threatening complications such as bleeding, thrombosis, and high output heart failure. In this report, we present a neonate who had a disproportionately hypertrophied left upper limb with port-wine stain, dystrophy of the left humerus, and hypertrophy of the left clavicle on X-ray, and arteriovenous malformation and massive dilatation of the left subclavian artery on magnetic resonance angiography. Exome sequencing analysis revealed a novel heterozygous splicing mutation (c.1776+2T>A) in the RASA1 gene. To the best of our knowledge, this report is the first case of RASA1-related Parkes Weber syndrome in Korea.

• Journal of Korean Neurosurgical Society
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• v.61 no.3
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• pp.333-342
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• 2018

Intracranial germ cell tumors (iGCTs) are a heterogeneous group of tumors with peculiar characteristics clearly distinguished from other brain tumors of neuroepithelial origin. Diverse histology, similarity to gonadal GCT, predilection to one sex, and geographic difference in incidence all present enigmas and fascinating challenges. The treatment of iGCT has advanced for germinoma to date; thus, clinical attention has shifted from survival to long-term quality of life. However, for non-germinomatous GCT, current protocols provide only modest improvement and more innovative therapies are needed. Recently, next-generation sequencing studies have revealed the genomic landscape of iGCT. Novel mutations in the KIT-RAS-MAPK and AKT-MTOR pathways were identified. More importantly, methylation profiling revealed a new method to assess the pathogenesis of iGCT. Molecular research will unleash new knowledge on the origin of iGCT and solve the many mysteries that have lingered on this peculiar neoplasm for a long time.