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Prostate cancer (PCa) is one of the most common cancer types and the fifth cancer-related cause of death among Western world men.  The sex steroid hormone, androgen and androgen receptor (AR) play important roles in PCa progression. Herewith, androgen deprivation therapy (ADT) is used as a regimen for PCa, but inevitably leads to development of castration-resistant PCa (CRPC) and distant metastasis. No effective treatment for metastatic PCa currently exists. Furthermore, it remains poorly understood whether and how the steroid hormone signaling in cooperation with multiple pathways that control proliferation, survival and invasion of cancer cells may contribute to metastatic dissemination and growth.

The aims of my PhD thesis focused on: (i) studying the clinical importance of estrogen- and androgen-related signaling pathways in promoting homing and metastatic growth of PCa cells in bone, (ii) gaining deeper understanding of the underlying mechanisms that facilitate PCa metastasis and treatment resistance, with focus on phosphatidylinositol-4-phosphate 5-kinase type-1 alpha (PIP5K1α), estrogen- and androgen receptor signaling, (iii) testing and characterizing the therapeutic potential of PIP5K1α inhibitor in combination with anti-estrogen or anti-androgen agents to improve treatment and overcome treatment resistance in CRPC.

In my thesis work we have shown that key biomarker genes exhibited unique expression profiles and signatures in PCa subtypes within large patient cohorts. Alterations in androgen- and estrogen-related biomarkers and PIP5K1α/Akt pathways were associated with poor patient outcome. We further discovered that CRPC cells and cancer stem-like cells utilized estrogen-associated factors including aromatase and estrogen receptor alpha (ERα), as well as cyclin A1, a key cell cycle regulator, to gain proliferative advantage, and to survive and metastasize to distant organs.

We found that the interaction between PIP5K1α and AR splice variant AR-V7 contributed to enzalutamide resistance. In series of in vivo treatment experiments using tumor xenograft mice, we demonstrated that ISA-2011B alone or in combination with enzalutamide had great therapeutic potential to suppress growth of tumors that had elevated levels of PI3K/Akt and AR-V7, and that were resistant to enzalutamide monotherapy.

We further showed that combination treatment using tamoxifen together with ISA-2011B selectively blocked elevated ERα/cyclin D1 and PIP5K1α/Akt, leading to tumor regression and had superior inhibitory effect over monotherapy in xenograft mice.

My studies therefore suggest that steroid hormone receptors, PIP5K1α signaling cascade and multiple cellular pathways cooperatively promote PCa progression. Taken together, the reported findings are the first to suggest a new therapeutic potential to inhibit or utilize the mechanisms related to ERα and PIP5K1α/Akt network, and provide a new therapeutic strategy to treat castration-resistant ER-positive subtype of tumors with metastatic potential.

Metastasis is the leading cause of cancer death because of a lack of early diagnosis tools and efficient treatment drugs. The lipid kinase phosphatidylinositol 4-phosphate 5 kinase (PIP5K1α) has been shown to play a vital role in the PI3K/AKT and KRAS signaling pathways. My PhD work, therefore, aims: (i) to study the role of PIP5K1α as a potential target for cancer treatment and the utility of its inhibitor ISA-2011B for the treatment of castration-resistant prostate cancer (CRPC) and pancreatic cancer, (ii) to establish genetically engineered mouse models and murine syngeneic models to recapitulate pancreatic cancer progression and test targeted anticancer drugs, (iii)  to utilize the state-of-the-art molecularly imprinting technique for cancer biomarker detection.

My thesis work has shown a clear inhibitory effect of ISA-2011B on human CRPC cell lines C4-2, DU145, and PC-3. The siRNA-mediated downregulation of PIP5K1α and ISA-2011B treatments both showed inhibition of the in vitro growth in all three cell lines. The PC-3 cell and its xenograft tumor can be inhibited by tamoxifen or ISA-2011B treatment alone, and a combination treatment from both compounds can selectively block the ERα and PIP5K1α/AKT network. The results, therefore, suggest that it is possible to treat CRPC by targeting PIP5K1α/AKT and ERα pathways.

We established the KPC [Krastm4Tyj Trp53tm1Brn Tg(Pdx1-Cre/Esr1*)] mouse model, in which spontaneous pancreatic ductal adenocarcinoma (PDAC) develops under tamoxifen induction. Three PDAC cell lines bearing KRASG12D and P53 mutations from spontaneous tumors were established and characterized. ISA-2011B in vitro treatment on those cell lines showed that KRASG12D and pErk were significantly decreased in at least one of the cell lines. It suggests that PIP5K1α is a potential target, and its inhibitor ISA-2011B is a promising drug for treating KRAS-mutated PDAC. The syngeneic PDAC model was also prepared by subcutaneous injection of the three cell lines back into the KPC mice, which will be used as an in vivo model to study the function of PIP5K1α in PDAC further.

We developed molecularly imprinted polymers (MIPs) for the potential biomarker Neu5Acα2-6GalNAcα-O-Ser/Thr (STn), as well as the non-imprinted polymers(NIPs) as a control. We identified human PDAC cell lines CFPAC-1 and BxPC-3 are STn-positive and -negative cells, respectively. Although STn-MIPs have a higher affinity than NIPs to both cancer cell lines, STn-MIPs cannot differentiate the STn-positive CFPAC-1 cells from the STn-negative BxPC-3 cells. It remains challenging to apply MIPs to detect biological molecules.

Our data provide a novel therapeutic strategy to treat advanced cancers such as CRPC and KRAS-mutated PDAC by targeting PIP5K1α-associate PI3K/AKT and/or KRAS signaling pathways.

Cancerspridning är den vanligaste orsaken till dödlighet. Det saknar förförande biomedicinska och diagnostiska metoder för tidigt upptäckten av cancer samt finns inte många effektiva och skrädd-sydda läkemedel. Lipidkinas såsom fosfatidylinositol 4-fosfat 5 kinas (PIP5K1α) har en viktig roll i styra cancer-specifika signalvägar PI3K/AKT och KRAS som ge upphov till cancerspridning. Målen för min doktorands forskningsprojekt är: (i) att studera rollen av PIP5K1α som ett potentiellt mål-protein i cancerspridning och testa PIP5K1α-hämmare ISA-2011B som läkemedel för att behandla aggressiva prostatacancer och bukspottkörtelcancer som är mycket dödliga cancertyper. (ii) att etablera genetiskt modifierade musmodeller som bära genetiska förändringar likande bukspottkörtelcancer i människor. Använda dessa musmodeller för att testa nya läkemedel för riktade behandling. (iii) att använda nya tekniken för att utveckla biomarkör för att upptäckten av cancer i tidigt fas.

Vi har visat att PIP5K1α-hämmare ISA-2011B ha goda och specifika effekter på prostatacancer celler. Behandling av cancerceller genom att hämma PIP5K1α gen- och protein-uttrycket led till cancercellens dödlighet och hämning av cancertillväxten i musmodeller och i cell-baserade modeller. Vidare har vi visade att läkemedel såsom östrogen-hämmare tamoxifen kan användas i kombination med ISA-2011B för att förhindra tumörtillväxt genom att selektivt blockera cancer signalvägar associerade med ERα, PIP5K1α/AKT-nätverket. Våra Resultat tyder på att det är möjligt att behandla prostatacancer genom att rikta in sig på PIP5K1α/AKT cancer-nätverket och/eller östrogen-vägen.

Vi etablerade genetiskt modifierade musmodeller som bära genetiska förändringar likande bukspottkörtelcancer i patienter. Vi testade effekt av ISA-2011B på tumörceller som odlade från tumör i dessa musmodeller. Vi har visat att ISA-2011B behandling led till minskade uttrycket av cancersignalvägar såsom KRASG12D och pErk. Våra resultat tyder på att PIP5K1α är ett lovande mål-protein, och dess hämmare ISA-2011B är ett potentiellt läkemedel för behandling av KRAS-muterad bukspottkörtelcancer. 

Vi utvecklade potentiella biomarkören som heter molekylärt präglade polymerer (MIPs) Neu5Acα2-6GalNAcα-O-Ser/Thr (STn). Vi visade att MIPs med STn kan känna igen cancerceller framförallt aggressiva bukspottkörtelcancer celler. Vi hoppas att STn-MIPs som nya biomarkör kan utvecklas vidare för att kunna upptäcka cancerceller i blodet, eftersom cancerceller i blodet har mycket högre halter av STn men inte normala blodceller. På så sätt patienter med risk att få eller ha bukspottkörtelcancer i tidig stadium kan få tidig diagnostik. 

Sammanfattningsvis våra studier kan bidra till en ny terapeutisk strategi för att behandla avancerad cancer och kan rikta in cancer-specifika PIP5K1α-associerade PI3K/AKT och KRAS-signalvägar.