The Role of an Oncoprotein CIP2A in Breast Cancer

Cancerous inhibitor of PP2A (CIP2A) is an oncoprotein expressed in several human cancer types. Previously, CIP2A has been shown to promote proliferation of cancer cells. Mechanistically, CIP2A is known to inhibit activity of a tumor suppressor protein phosphatase 2A (PP2A) towards an oncoprotein MYC, further stabilizing MYC in human cancer. However, the molecular mechanisms how CIP2A expression is induced during cellular transformation are not well known. Also, expression, functional role and clinical relevance of CIP2A in breast cancer had not been studied before. The results of this PhD thesis work demonstrate that CIP2A is highly expressed in human breast cancer, and that high expression of CIP2A in tumors is a poor prognostic factor in a subset of breast cancer patients. CIP2A expression correlates with inactivating mutations of tumor suppressor p53 in human cancer. Notably, we demonstrate that p53 inactivation up-regulates CIP2A expression via increased expression of an oncogenic transcription factor E2F1. Moreover, CIP2A promotes expression of E2F1, and this novel positive feedback loop between E2F1 and CIP2A is demonstrated to regulate sensitivity to both p53-dependent and -independent senescence induction in breast cancer cells. Importantly, in a CIP2A deficient breast cancer mouse model, abrogation of CIP2A attenuates mammary tumor formation and progression with features of E2F1 inhibition and induction of senescence. Furthermore, we demonstrate that CIP2A expression defines the cellular response to a senescence-inducing chemotherapy in breast cancer. Taken together, these results demonstrate that CIP2A is an essential promoter of breast cancer tumor growth by inhibiting senescence. Finally, this study implicates inhibition of CIP2A as a promising therapy target for breast cancer.

Ett rätt barna-klenodium

Motto [I]: Psal. 19: v. 11. Herrans bod äro klara, ... Motto [II]: Rom. I: v. 16. Evangelium är Guds kraft ... Motto [III]: Matth. 18: v. 3. Vthan j omwänden eder och warden såsom barn, .. Nimiön kehyslauselma: Psal. 34. v. 12. Kommer hijt, barn, hörer mig: .. Priv.: Henrik Christofer Merckell. Arkit: A-D12 E6.

De nomine, grammatico-pragmatica

Painovuosi nimekkeestä.

Identification and characterization of CIP2A as a novel oncogenic inhibitor of PP2A

Inhibition of the tumor suppressor protein phosphatase 2A (PP2A) activity has been identified as one of the five key alterations required for human cell transformation. Regardless of this crucial role in human cancer development, the detailed mechanisms by which PP2A inhibition occurs in human cancers remain largely uncharacterized. PP2A regulates a plethora of cellular signaling cascades. One of the targets of PP2A is Myc oncoprotein, which is destabilized and degraded in response to PP2A-mediated dephosphorylation of Myc serine 62. In this study we identify Cancerous Inhibitor of PP2A (CIP2A) as a previously uncharacterized endogenous inhibitor of PP2A in human cancer cells. CIP2A inhibits PP2A activity leading to subsequent stabilization of the Myc protein. CIP2A promotes malignant growth of cancer cells in vitro and xenograft tumor formation in vivo and is overexpressed in cancer. Moreover, we explored the effect of CIP2A on global transcriptional profiles and validated a CIP2A-dependent transcriptional signature. Analysis of the CIP2A signature revealed both Myc-dependent and -independent functions for CIP2A. Importantly, we demonstrate that the CIP2A signature has clinical relevance in human breast cancer subtypes. Finally, we identify the genes potentially mediating the long-term growth suppression in CIP2A depleted cancer cells. Taken together, this work identifies CIP2A as a novel human oncoprotein and describes its function in cancer cells. These results may open novel possibilities for patient stratification and therapeutic intervention of cancer.

Libyan breast cancer: Health services and biology. Diagnosis delay and prognostic value of DNA pploidy, S-phase fraction, and Ki-67 and Bcl-2 immunohistochemistry

The aim of this study was to investigate the diagnosis delay and its impact on the stage of disease. The study also evaluated a nuclear DNA content, immunohistochemical expression of Ki-67 and bcl-2, and the correlation of these biological features with the clinicopathological features and patient outcome. 200 Libyan women, diagnosed during 2008–2009 were interviewed about the period from the first symptoms to the final histological diagnosis of breast cancer. Also retrospective preclinical and clinical data were collected from medical records on a form (questionnaire) in association with the interview. Tumor material of the patients was collected and nuclear DNA content analysed using DNA image cytometry. The expression of Ki-67 and bcl-2 were assessed using immunohistochemistry (IHC). The studies described in this thesis show that the median of diagnosis time for women with breast cancer was 7.5 months and 56% of patients were diagnosed within a period longer than 6 months. Inappropriate reassurance that the lump was benign was an important reason for prolongation of the diagnosis time. Diagnosis delay was also associated with initial breast symptom(s) that did not include a lump, old age, illiteracy, and history of benign fibrocystic disease. The patients who showed diagnosis delay had bigger tumour size (p<0.0001), positive lymph nodes (p<0.0001), and high incidence of late clinical stages (p<0.0001). Biologically, 82.7% of tumors were aneuploid and 17.3% were diploid. The median SPF of tumors was 11% while the median positivity of Ki-67 was 27.5%. High Ki-67 expression was found in 76% of patients, and high SPF values in 56% of patients. Positive bcl-2 expression was found in 62.4% of tumors. 72.2% of the bcl-2 positive samples were ER-positive. Patients who had tumor with DNA aneuploidy, high proliferative activity and negative bcl-2 expression were associated with a high grade of malignancy and short survival. The SPF value is useful cell proliferation marker in assessing prognosis, and the decision cut point of 11% for SPF in the Libyan material was clearly significant (p<0.0001). Bcl-2 is a powerful prognosticator and an independent predictor of breast cancer outcome in the Libyan material (p<0.0001). Libyan breast cancer was investigated in these studies from two different aspects: health services and biology. The results show that diagnosis delay is a very serious problem in Libya and is associated with complex interactions between many factors leading to advanced stages, and potentially to high mortality. Cytometric DNA variables, proliferative markers (Ki-67 and SPF), and oncoprotein bcl-2 negativity reflect the aggressive behavior of Libyan breast cancer and could be used with traditional factors to predict the outcome of individual patients, and to select appropriate therapy.

Ihmisen papilloomavirustyypin (HPV) 16 pitkän säätelyalueen HPV16 E2-proteiinien sitoutumiskohtien (E2BS) metylaatioiden tutkimusmenetelmän pystytys

Ihmisen papilloomavirukset (HPV) on yhdistetty arviolta 28 %:iin virusten aiheuttamista syövistä, joista yksi esiintymispaikka on pään ja kaulan alue. Metylaatio on yksi syövän syntyyn liitetty muutos solujen genomissa. Tämän syventävän työn tutkimuksen aiheena oli metylaatiomuutosten vaikutus E2-proteiinien sitoutumisessa HPV-tyypin 16 genomin onkogeeneina tunnettujen E6- ja E7-geenien alueelle (E2BS). Tarkoituksena oli pystyttää tutkimuslinja, jolla kyseisten sitoutumisalueiden metylaatioasteiden muutokset ja variaatiot voitaisiin havaita HPV-infektoituneissa solulinjoissa. Lähtökohtana käytettiin Chaiwongkot ym. (2012) aiheesta julkaisemaa artikkelia, jonka tulokset pyrittiin toistamaan. Matalan (SiHa) ja korkean (CaSki) asteen HPV-infektoiduista kohdunkaulan levyepiteelisyöpäsolulinjoista eristetty DNA bisulfiittikäsiteltiin, monistettiin PCR:llä ja pyrosekvenoitiin. Saatujen sekvenssien metylaatioasteita verrattiin keskenään sekä aiempiin tutkimuksiin. Tässä syventävien opintojen työssä saatiin pääosin toistettua Chaiwongkotin ym. (2012) saadut tulokset CaSki- ja SiHa-solujen metylaatiosta. CaSki-soluilla E2BS1-alueen metylaatioaste oli keskimäärin 38–42 % (s± 4,1–4,3), E2BS2-alueen 13 % (s± 0,6) ja E2BS3-4alueella 92–99 % (s± 11–42). SiHa-soluilla vastaavat luvut olivat 4-7 %, 2 % ja 5-8 %. CaSki- ja SiHa-soluilla E2BS-alueiden metylaatio oli verrannollinen HPV:n suureen kopiolukuun. Vähäisin merkitys oli E2BS2-alueella, kun taas E2BS1- ja E2BS3-4-alueet olivat vahvemmin metyloituneet. Menetelmässä kohdattuihin ongelmiin kuului E2BS1-alueen pyrosekvenointitulosten jääminen virhemarginaalien ulkopuolelle sekä itse pyrosekvenointimenetelmä.