Context-Specific Efficacy of Apalutamide Therapy in Preclinical Models of Pten-Deficient Prostate Cancer.

Significant improvements with apalutamide, a nonsteroidal antiandrogen used to treat patients suffering from advanced prostate cancer (PCa), have prompted evaluation for additional indications and therapeutic development with other agents; however, persistent androgen receptor (AR) signaling remains problematic. We used autochthonous mouse models of Pten-deficient PCa to examine the context-specific antitumor activity of apalutamide and profile its molecular responses. Overall, apalutamide showed potent antitumor activity in both early-stage and late-stage models of castration-naïve prostate cancer (CNPC). Molecular profiling by Western blot and immunohistochemistry associated persistent surviving cancer cells with upregulated AKT signaling. While apalutamide was ineffective in an early-stage model of castration-resistant prostate cancer (CRPC), it tended to prolong survival in late-stage CRPC. Molecular features associated with surviving cancer cells in CRPC included upregulated aberrant-AR, and phosphorylated S6 and proline-rich Akt substrate of 40 kDa (PRAS40). Strong synergy was observed with the pan-AKT inhibitor GSK690693 and apalutamide in vitro against the CNPC- and CRPC-derived cell lines and tended to improve the antitumor responses in CNPC but not CRPC in vivo. Upregulation of signal transducer and activator of transcription 3 (STAT3) and proviral insertion in murine-1 (PIM-1) were associated with combined apalutamide/GSK690693. Our findings show that apalutamide can attenuate Pten-deficient PCa in a context-specific manner and provides data that can be used to further study and, possibly, develop additional combinations with apalutamide.

[Identification of the Risk Factors for Cabazitaxel-Induced Neutropenia with Preventive Administration of Pegfilgrastim].

Prophylaxis using pegfilgrastim is recommended to prevent cabazitaxel-induced neutropenia. We observed GradeB3 neutropenia in a patient after administration of cabazitaxel, despite prophylaxis using pegfilgrastim. To identify the risk factors associated with GradeB3 neutropenia, we retrospectively investigated the records of 10 patients who received prophylaxis with pegfilgrastim after administration of cabazitaxel. They were divided into GradeB3 neutropenia and non-GradeB3 neutropenia groups, and we compared the background data and laboratory values between the 2 groups. A univariate analysis revealed that hypoalbuminemia was significantly observed in patients with cabazitaxel-induced GradeB3 neutropenia. The incidence of GradeB3 neutropenia was significantly high in patients with serum albumin levels<3.6 g/dL. Cabazitaxel has a high rate of protein binding; moreover, serum albumin levels<3.6 g/dL might be associated with high concentrations of unbound cabazitaxel, and thus an increase in the incidence of GradeB3 neutropenia. Therefore, hypoalbuminemia at the time of administration of cabazitaxel may be a risk factor related to the development of GradeB3 neutropenia.

[Retrospective Investigation of the Risk Factors for Severity in Panitumumab-Induced Hypomagnesemia].

Hypomagnesemia caused by panitumumab can often lead to severe adverse effects, such as arrhythmia. However, the risk factors are still controversial. To clarify the risk factors and time to onset of panitumumab-induced hypomagnesemia, we retrospectively investigated the records of 30 patients who had received panitumumab. They were divided into Grade B2 hypomagnesemia and non-Grade B2 hypomagnesemia groups, according to their serum magnesium levels, and we compared patients' backgrounds, laboratory values, and concomitant drugs between the 2 groups. Univariate analysis revealed that hypocalcemia and non-administration of an oral magnesium preparation were significantly associated with Grade B2 hypomagnesemia induced by panitumumab. Incipient grade 1 hypocalcemia was observed after incipient Grade 1 hypomagnesemia in both groups. The occurrence of these complications was significant in the Grade B2 hypomagnesemia group. Thereafter, in all patients of the Grade B2 hypomagnesemia group that exhibited both complications, hypomagnesemia developed to Grade 2 or higher. The development of Grade 3 and Grade 4 hypomagnesemia without the development of Grade 2 hypomagnesemia was observed in 2 patients each. Thus, aggravation of hypomagnesemia can be expected upon the administration of panitumumab, and therefore, not only serum magnesium levels, but also serum calcium levels need to be monitored.

Conditional PTEN-deficient mice as a prostate cancer chemoprevention model.

BACKGROUND: We generated a mouse model of prostate cancer based on the adult-prostate-specific inactivation of phosphatase and tensin homolog (PTEN) using the Cre-loxP system. The potential of our mice as a useful animal model was examined by evaluating the chemopreventive efficacy of the anti-androgen, chlormadinone acetate (CMA). MATERIALS AND METHODS: Six-week-old mice were treated subcutaneously with 50 µg/g of CMA three times a week for 9 or 14 weeks and sacrificed at weeks 15 and 20. Macroscopic change of the entire genitourinary tract (GUT) and histologically evident prostate gland tumor development were evaluated. Proliferation and apoptosis status in the prostate were examined by immunohistochemistry. RESULTS: CMA triggered significant shrinkage of not only the GUT but also prostate glands at 15 weeks compared to the control (p=0.017 and p=0.010, respectively), and the trend became more marked after a further five-weeks of treatment. The onset of prostate adenocarcinoma was not prevented but the proliferation of cancer cells was inhibited by CMA, which suggested the androgen axis is critical for cancer growth in these mice. CONCLUSIONS: Conditional PTEN-deficient mice are useful as a preclinical model for chemoprevention studies and serve as a valuable tool for the future screening of potential chemopreventive agents.

Possible clinical cure of metastatic breast cancer: lessons from our 30-year experience with oligometastatic breast cancer patients and literature review.

BACKGROUND: Metastatic breast cancer (MBC) is generally incurable. However, 10-20-year relapse-free survival of MBC is approximately 2%, implying that at least a small subset of MBC patients achieve prolonged survival. We therefore analyzed long-term outcome in a particular subset, i.e., oligometastatic breast cancer (OMBC). METHODS: Data of OMBC subjects (N = 75) treated in our institution from April 1980 to March 2010 were retrospectively analyzed. OMBC was identified as: one or 2 organs involved with metastatic lesions (excluding the primary lesion resectable by surgery), fewer than 5 lesions per metastasized organ, and lesion diameter less than 5 cm. Patients were generally treated with systemic chemotherapy first, and those who achieved complete response (CR) or partial response (PR) were further treated, if applicable, with local therapy (surgical or radiation therapy) to maintain CR or to induce no evidence of clinical disease (NED), with additional systemic therapy. RESULTS: Median follow-up duration was 103 (6-329) months. Single or 2 organs were involved in, respectively, 44 (59%) and 31 (41%) cases with metastatic lesions, 48% of which were visceral. In cases where effects of systemic therapy, possibly in combination with other treatments, were evaluated (N = 68), CR or PR was achieved in 33 (48.5%) or 32 (47.1%), respectively, with overall response rate (ORR: CR + PR) of 95.6% (N = 65). In cases receiving multidisciplinary treatment (N = 75), CR or NED (CR/NED), or PR was induced in 48 (64.0%) or 23 (30.7%) cases, respectively, with ORR (CR/NED + PR) of 94.7% (N = 71). CR rates (60.5%) with systemic therapy and CR/NED rates (79.5%) with multidisciplinary treatment were significantly better in subjects with a single involved organ than in those with two involved organs (P = 0.047 and 0.002, systemic only or multidisciplinary treatments, respectively). Medians estimated by Kaplan-Meier method were: overall survival (OS) of 185.0 months and relapse-free interval (RFI) of 48.0 months. Estimated outcomes were: OS rates (OSR) of 59.2% at 10 years and 34.1% at 20 years, and relapse-free rates (RFR) of 27.4% at 10 years and 20 years. No disease progression was observed after 101.0 months as RFR. Cases with single organ involvement (N = 44) showed significantly better outcomes (OSR of 73% at 10 years and 52% at 20 years, RFR of 42% at 10 years and 20 years). Those who received local therapies (N = 35) also showed better prognosis: OSR of 82% at 10 years and 53% at 20 years, RFR of 38% at 10 years and 20 years. Three cases (4%) survived for their lifetime without relapse after achieving CR or NED, our definition of clinical cure. Multivariate analysis revealed factors favoring better prognosis as: none for OS, and single organ involvement with metastasis, administration of local treatment, and shorter disease-free interval (DFI) (P = 0.030, 0.039, and 0.042, respectively) for RFR. Outcomes in OMBC in literature were OSR of 35-73% at 10 years and 26-52% at 20 years, and RFR of 27-42% at 10 years and 26-42% at 20 years. CONCLUSIONS: The present analyses clearly indicate that OMBC is a distinct subgroup with long-term prognosis superior to MBC, with reasonable provability for clinical cure. Further prospective studies to better characterize OMBC are warranted to improve prognosis in MBC.