SH3YL1 cooperates with ESCRT-I in the sorting and degradation of the EGF receptor.

Ubiquitinated membrane proteins such as epidermal growth factor receptor (EGFR) are delivered to early endosomes and then sorted to lysosomes via multivesicular bodies (MVBs) for degradation. The regulatory mechanism underlying formation of intralumenal vesicles en route to generation of MVBs is not fully understood. In this study, we found that SH3YL1, a phosphoinositide-binding protein, had a vesicular localization pattern overlapping with internalized EGF in endosomes in the degradative pathway. Deficiency of SH3YL1 prevents EGF trafficking from early to late endosomes and inhibits degradation of EGFR. Moreover, we show that SH3YL1 mediates EGFR sorting into MVBs in a manner dependent on its C-terminal SH3 domain, which is necessary for the interaction with an ESCRT-I component, Vps37B. Taken together, our observations reveal an indispensable role of SH3YL1 in MVB sorting and EGFR degradation mediated by ESCRT complexes.

Microsatellite instability and mismatch repair protein expressions in lymphocyte-predominant breast cancer.

The frequency of microsatellite instability (MSI) is reportedly extremely low in breast cancer, despite widespread clinical expectations that many patients would be responsive to immune-checkpoint inhibitors (ICI). Considering that some triple-negative breast cancers (TNBC) responded well to ICI in a clinical trial and that a high density of tumor-infiltrating lymphocytes (TILs) is frequently observed in other cancers with high levels of microsatellite instability (MSI-H), we hypothesized that some TNBC with a high density of TILs would be MSI-H. Medullary carcinoma (MedCa) of the breast, a rare histological type, is characterized by a high density of TILs. Considering that MedCa of the colon is often MSI-H, we suspected that MedCa in breast cancer might also include MSI-H tumors. Therefore, we conducted MSI tests on such breast cancers with a high density of TILs. The MSI status of 63 TIL-high TNBC and 38 MedCa tumors, all from Asian women who had undergone curative surgery, were determined retrospectively. DNA mismatch repair (MMR) proteins and PD-L1 expression were also investigated immunohistochemically. All samples were microsatellite stable, being negative for all microsatellite markers. TIL-high TNBC with low MLH1 protein had higher levels of PD-L1 in stromal immune cells (P = .041). MedCa tumors showed significantly higher PD-L1 expression in immune cells than in TIL-high TNBC (<.001). We found that MSI-H tumors were absent in TIL-high breast cancers. Examination of MMR proteins, not a purpose of Lynch syndrome screening, may merit further studies to yield predictive information for identifying patients who are likely to benefit from ICI.

Analysis of circulating tumour cell and the epithelial mesenchymal transition (EMT) status during eribulin-based treatment in 22 patients with metastatic breast cancer: a pilot study.

BACKGROUND: Liquid biopsy approaches, such as measuring circulating tumour cells (CTCs), have recently been introduced in several clinical studies. However, the development of CTCs as a predictive marker for treatment effects on breast cancer remains an enormous task. We investigated CTCs, including epithelial mesenchymal transition (EMT) status, from metastatic breast cancer patients who had received eribulin-based treatment, which reportedly suppresses EMT as a means of tumour suppression. Our aim was to test the possibility of this method serving as a tool predicting eribulin efficacy. METHODS: Twenty-two patients were enrolled and peripheral blood samples were collected before eribulin treatment. CTCs were then examined using a Microfluidic Chip device. CTCs positive for vimentin and pan-cytokeratin were defined as mesenchymal and epithelial CTCs, respectively. Progression-free survival (PFS) and clinical response were assessable in 20 and 18 patients, respectively, in relation to the number of CTCs. RESULTS: Numbers of total CTCs were significantly increased in patients with progressive disease during treatment (p = 0.006). Median PFS was 14.6 weeks and patients with more total and mesenchymal CTCs at baseline had significantly shorter PFS (p = 0.0013 and 0.013, respectively). Multivariate logistic regression analysis revealed small number of total baseline CTCs and long disease-free survival to be related to long PFS (p = 0.0004 and 0.020, respectively). CONCLUSIONS: Our data suggest that determining both mesenchymal and epithelial CTCs at baseline might be a good tool for predicting eribulin responsiveness. Evaluation of mesenchymal CTC can be considered as a parameter in larger studies, while most clinical trials are currently employing only the detection of the epithelial cellular adhesion molecule (EpCAM).

Multifunctional bioscaffolds for 3D culture of melanoma cells reveal increased MMP activity and migration with BRAF kinase inhibition.

Matrix metalloproteinases (MMPs) are important for many different types of cancer-related processes, including metastasis. Understanding the functional impact of changes in MMP activity during cancer treatment is an important facet not typically evaluated as part of preclinical research. With MMP activity being a critical component of the metastatic cascade, we designed a 3D hydrogel system to probe whether pharmacological inhibition affected human melanoma cell proteolytic activity; metastatic melanoma is a highly aggressive and drug-resistant form of skin cancer. The relationship between MMP activity and drug treatment is unknown, and therefore we used an in situ fluorogenic MMP sensor peptide to determine how drug treatment affects melanoma cell MMP activity in three dimensions. We encapsulated melanoma cells from varying stages of progression within PEG-based hydrogels to examine the relationship between drug treatment and MMP activity. From these results, a metastatic melanoma cell line (A375) and two inhibitors that inhibit RAF (PLX4032 and sorafenib) were studied further to determine whether changes in MMP activity led to a functional change in cell behavior. A375 cells exhibited increased MMP activity despite an overall decrease in metabolic activity with PLX4032 treatment. The changes in proteolytic activity correlated with increased cell elongation and increased single-cell migration. In contrast, sorafenib did not alter MMP activity or cell motility, showing that the changes induced by PLX4032 were not a universal response to small-molecule inhibition. Therefore, we argue the importance of studying MMP activity with drug treatment and its possible implications for unwanted side effects.

Regulation of CD44 expression and focal adhesion by Golgi phosphatidylinositol 4-phosphate in breast cancer.

CD44, a transmembrane receptor, is expressed in the standard or variant form and plays a critical role in tumor progression and metastasis. This protein regulates cell adhesion and migration in breast cancer cells. We previously reported that phosphatidylinositol-4-phosphate (PI(4)P) at the Golgi regulates cell migration and invasion in breast cancer cell lines. In this study, we showed that an increase in PI(4)P levels at the Golgi by knockdown of PI(4)P phosphatase SAC1 increased the expression of standard CD44, variant CD44, and ezrin/radixin phosphorylation and enhanced the formation of focal adhesions mediated by CD44 and ezrin/radixin in MCF7 and SK-BR-3 cells. In contrast, knockdown of PI 4-kinase IIIß in highly invasive MDA-MB-231 cells decreased these factors. These results suggest that SAC1 expression and PI(4)P at the Golgi are important in tumor progression and metastasis and are potential prognostic markers of breast cancers.

Activated Caspase 3 Expression in Remnant Disease After Neoadjuvant Chemotherapy May Predict Outcomes of Breast Cancer Patients.

BACKGROUND: A number of studies have indicated that patients obtaining a pathological complete response (pCR) from neoadjuvant chemotherapy (NAC) have a good prognosis; however, prognostic factors for non-pCR patients are not yet well-established. By examining remnant cancer in non-pCR patients, the expression of cleaved Caspase 3 (Casp3), an activated apoptotic marker, was immunohistochemically investigated to determine whether this protein has the potential to serve as a novel marker for predicting patient outcomes. METHODS: We investigated 218 patients with invasive breast cancer who received NAC and underwent surgery during the 2006 through 2008 period at our institution. Following surgery, standard adjuvant endocrine therapy was administered if a tumor was hormone receptor-positive. Casp3 was evaluated in remnant cancer based on the number of positive cells in five high-power fields. RESULTS: pCR was obtained in 49 patients, and 50 of the 169 non-pCR patients developed recurrences during the median 82-month observation period. We found large tumor size, lymph node involvement, lymph vessel invasion, estrogen receptor-negative, progesterone receptor-negative, high Ki67 and high Casp3 expression to be factors related to tumor recurrence. A logistic regression model revealed that lymph node involvement, as well as high Ki67 and Casp3, to be factors independently predicting recurrence, while lymph vessel invasion and high Ki67 expression were found to be related to breast cancer mortality. CONCLUSIONS: Patients with remnant cancer showing high Casp3 expression had poor outcomes. Our results showed that Casp3 is a potential prognostic marker for non-pCR patients.

Ki67 expression and the effect of neo-adjuvant chemotherapy on luminal HER2-negative breast cancer.

BACKGROUND: Patients with luminal HER2-negative tumours have a favourable prognosis. However, there is a subpopulation in which poorer outcomes are obtained with endocrine therapy alone. This subpopulation is considered to benefit from chemotherapy. However, the significance of chemotherapy for those with luminal tumours has decreased due to recent changes in treatment strategies. Thus, it is often difficult to determine whether we should recommend chemotherapy to such patients in clinical practice. We investigated Ki67 expression, as a means of predicting the responses of luminal HER2-negative breast cancer patients to neo-adjuvant chemotherapy (NAC), in order to identify a subpopulation that would benefit from these treatments. METHODS: We enrolled 114 luminal HER2-negative breast cancer patients undergoing surgery after NAC. Biomarkers were examined using biopsy specimens obtained prior to treatment, to avoid any chemotherapy-related effects. Chemotherapy effects were determined employing operative specimens and we defined pathological complete response (pCR) as invasive nest disappearance, based only on the primary breast tumour. We applied receiver operating characteristic curve analysis to data from our 114 patients, to investigate Ki67 expression as a predictor of pCR. RESULTS: The pCR rate was significantly higher for tumours with high Ki67 expression (p < 0.01) and all patients who obtained pCR remained recurrence-free during the median 58-month observation period. We identified 35% as the Ki67 cut-off value which distinguishes those with a pCR from other cases. Another dataset, comprised of 196 patients with a median 29-month observation period, was recruited for validation. Disease-free survival was found to be significantly (p < 0.01) lower in the patients with tumours in which Ki67 expression was higher than 35%. CONCLUSION: Our results raise the possibility of the luminal HER2-negative subpopulation with Ki67 expression higher than 35% benefiting from chemotherapy, as evidenced by improved survival.

Association between specific human leukocyte antigen alleles and development of thyroid immune-related adverse event.

Aim: Inherent variations in human leukocyte antigen (HLA) alleles have been revealed epidemiologically to influence the development of autoimmune diseases. HLA alleles may thus also be associated with the development of immune-related adverse events (irAEs), such as thyroid irAE. Materials & methods: In this case-control study, 71 cancer patients who received immune checkpoint inhibitors were enrolled and HLA-genotyped and the frequency of HLA alleles was compared. Results: A*26:01, DPA1*01:03 and DPB1*02:01 were significantly more frequent in patients with thyroid irAE than in patients without any irAEs (35.0 vs 3.2% [p = 0.004], 80.0 vs 45.2% [p = 0.020] and 55.0 vs 25.8% [p = 0.044], respectively). Conclusion: A*26:01, DPA1*01:03 and DPB1*02:01 appear to be associated with thyroid irAE.

Everyone has a unique combination of human leukocyte antigens (HLAs) in their body that help the immune system identify threats. HLAs were named from the fact that they were first identified on the surface of human leukocytes. Afterward, HLAs were also found on all human cells. HLAs present antigens to immune cells. These HLAs also influence how the immune system attacks cancer cells. Immune checkpoint inhibitors are drugs that can help the immune system fight cancer, but they sometimes cause severe adverse events. In this study, we investigated whether specific HLA genes are related to the development of an adverse event that affects the thyroid in cancer patients treated with immune checkpoint inhibitors. We found an association between three HLA genes (A*26:01, DPA1*01:03 and DPB1*02:01) and the development of the thyroid adverse event. However, larger studies are needed to confirm and generalize these initial exploratory findings.

The Impact of Being Underweight on the Prognosis of Older Patients With Early Breast Cancer.

Background/Aim: The number of older patients with breast cancer has been increasing and a major challenge is to develop optimal treatment strategies for these patients, who often have comorbidities. Obesity is reportedly a poor prognostic factor in breast cancer, however there is limited research on underweight patients. Clarifying the relationship between physique and prognosis may contribute to the establishment of optimal treatment strategies for older patients with breast cancer. Patients and Methods: This retrospective study examined clinicopathological data from a multicenter collaborative database on 1,076 patients aged 70 years or older who had undergone curative surgery. According to the body mass index (BMI), patient physique was defined as underweight (<18.5 kg/m2), normal (18.5-24.9 kg/m2) or obese (≥25 kg/m2). In this study, we explored the relationship between the physique of patients with breast cancer and outcomes. Results: Underweight patients had a significantly lower rate of chemotherapy administration (p=0.017) and a higher rate of presence of other cancer (p=0.022). During the observation period (median of 75.2 months), 133 patients (12%) developed recurrent disease and 131 patients (12%) died. Age, BMI, tumor size, progesterone receptor and the presence of other cancer were independent factors relating to overall survival (p<0.001, p=0.027, p=0.002, p=0.008 and p=0.005, respectively). Patients with a low BMI had a significantly shorter overall survival, but there was no association with disease-free survival in this subset of patients. Conclusion: Overall survival was shorter in underweight older patients with breast cancer. Our data indicate that being underweight should be considered both in treatment decisions and in future studies of outcomes for older patients with breast cancer.

E3 Ubiquitin Ligase NEDD4 Affects Estrogen Receptor α Expression and the Prognosis of Patients with Hormone Receptor-Positive Breast Cancer.

Neural precursor cell-expressed developmentally downregulated 4-1 (NEDD4) is an E3 ligase that leads to the degradation of proteins, including estrogen receptor α. We evaluated whether the expression level of NEDD4 affected the outcome of breast cancer patients. We performed a retrospective cohort study enrolling 143 patients with hormone receptor-positive, human epidermal growth factor receptor 2-negative early breast cancer. Of the 66 patients with high NEDD4 mRNA levels (high NEDD4 group) and 77 patients with low NEDD4 mRNA levels (low NEDD4 group), 98.4% and 96.1%, respectively, of the patients had received neoadjuvant/adjuvant hormone therapy. Disease-free survival and overall survival were significantly longer in the low NEDD4 group than in the high NEDD4 group (p = 0.048 and p = 0.022, respectively). Western blotting revealed a high expression of estrogen receptor α in the NEDD4-knockdown culture cells. The proliferation of NEDD4-knockdown cells treated with tamoxifen or estradiol deprivation was suppressed, compared with that of NEDD4-expressing cells. Knockdown of NEDD4 in breast cancer cells induced the accumulation of estrogen receptor α and increased sensitivity to hormone therapy. In summary, this mechanism may lead to a better prognosis in hormone receptor-positive breast cancer patients with a low expression of NEDD4.

The Japanese Breast Cancer Society Clinical Practice Guidelines for systemic treatment of breast cancer, 2022 edition.

The Japanese Breast Cancer Society (JBCS) Clinical Practice Guidelines for systemic treatment of breast cancer were updated to the 2022 edition through a process started in 2018. The updated guidelines consist of 12 background questions (BQs), 33 clinical questions (CQs), and 20 future research questions (FRQs). Multiple outcomes including efficacy and safety were selected in each CQ, and then quantitative and qualitative systematic reviews were conducted to determine the strength of evidence and strength of recommendation, which was finally determined through a voting process among designated committee members. Here, we describe eight selected CQs as important updates from the previous guidelines, including novel practice-changing updates, and recommendations based on evidence that has emerged specifically from Japanese clinical trials.

Quantification and visualization of phosphoinositides by quantum dot-labeled specific binding-domain probes.

Phosphoinositides (PI) play important regulatory roles in cell physiology. Localization and quantitation of PIs within the cell is necessary to understand their precise function. Currently, ectopic expression of green fluorescent protein (GFP)-fused PI-binding domains is used to visualize PIs localized to the cell membrane. However, ectopically expressed PI-binding domains may compete with endogenous binding proteins, thus altering the physiological functions of the PIs. Here, we establish a novel method for quantification and visualization of PIs in cells and tissue samples using PI-binding domains labeled with quantum dots (Qdot) as specific probes. This method allowed us to simultaneously quantify three distinct PIs, phosphatidylinositol 3,4,5-triphosphatase [PtdIns(3,4,5)P(3)), PtdIns(3,4)P(2), and PtdIns(4,5)P(2), in crude acidic lipids extracted from insulin-stimulated cells. In addition, the method allowed the PIs to be visualized within fixed cells and tissues. Sequential and spatial changes in PI production and distribution were detected in platelet-derived growth factor (PDGF)-stimulated NRK49F cells. We also observed accumulation of PtdIns(3,4)P(2) at the dorsal ruffle in PDGF-stimulated NIH3T3 cells. Finally, we found PtdIns(3,4,5)P(3) was enriched in lung cancer tissues, which also showed high levels of phosphorylated Akt. Our new method to quantify and visualize PIs is expected to provide further insight into the role of lipid signaling in a wide range of cellular events.

Estrogen receptor-α directly regulates sensitivity to paclitaxel in neoadjuvant chemotherapy for breast cancer.

Neoadjuvant chemotherapy (NAC) has become the standard treatment for advanced breast cancer. Several prognostic markers, including estrogen receptor-α (ERα), are used to predict the response to NAC. However, the molecular significance of ERα expression in the efficacy of chemotherapy is not yet fully understood. To examine this issue, we first evaluated ERα transcriptional activity in breast cancer cells derived from pre-NAC specimens using estrogen response element-green fluorescent protein (ERE-GFP) as a reporter gene, and found that, in the cases for which ERα activities determined by GFP expression were not detected or low, pCR (pathological complete response) could be achieved even though ERα protein was expressed. Next, we examined the effects of alterations in ERα expression levels on sensitivity to paclitaxel, a key drug in NAC, by stable expression of ERα in ER-negative SKBR3 cells and by siRNA-mediated down-regulation of ERα in ER-positive MCF-7 cells, and showed that ERα expression and sensitivity to paclitaxel showed an inverse correlation. We also established paclitaxel-resistant MCF-7 cell clones and found that they have higher estrogen-induced ER activity than parent cells. Paclitaxel is a microtubule-stabilizing agent, while HDAC6 (histone deacetylase 6), which we previously identified as an estrogen-regulated gene, enhances cell motility by destabilizing microtubules via deacetylation of α-tubulin. Finally, we demonstrate herein that ERα knockdown in MCF-7 cells prevents deacetylation of α-tubulin, thereby increasing sensitivity to paclitaxel. Taken together, these results suggest that ERα expression directly regulates sensitivity to paclitaxel in NAC for breast cancer via the effect on microtubule stability.

PP2A-dependent TFEB activation is blocked by PIKfyve-induced mTORC1 activity.

Transcriptional factor EB (TFEB) is a master regulator of genes required for autophagy and lysosomal function. The nuclear localization of TFEB is blocked by the mechanistic target of rapamycin complex 1 (mTORC1)-dependent phosphorylation of TFEB at multiple sites including Ser-211. Here we show that inhibition of PIKfyve, which produces phosphatidylinositol 3,5-bisphosphate on endosomes and lysosomes, causes a loss of Ser-211 phosphorylation and concomitant nuclear localization of TFEB. We found that while mTORC1 activity toward S6K1, as well as other major mTORC1 substrates, is not impaired, PIKfyve inhibition specifically impedes the interaction of TFEB with mTORC1. This suggests that mTORC1 activity on TFEB is selectively inhibited due to loss of mTORC1 access to TFEB. In addition, we found that TFEB activation during inhibition of PIKfyve relies on the ability of protein phosphatase 2A (PP2A) but not calcineurin/PPP3 to dephosphorylate TFEB Ser-211. Thus when PIKfyve is inhibited, PP2A is dominant over mTORC1 for control of TFEB phosphorylation at Ser-S211. Together these findings suggest that mTORC1 and PP2A have opposing roles on TFEB via phosphorylation and dephosphorylation of Ser-211, respectively, and further that PIKfyve inhibits TFEB activity by facilitating mTORC1-dependent phosphorylation of TFEB.

Is adjuvant chemotherapy necessary in older patients with breast cancer?

BACKGROUND: Due to the lack of clinical trials on the efficacy of chemotherapy in older patients, an optimal treatment strategy has not been developed. We investigated whether adjuvant chemotherapy could improve the survival of older patients with breast cancer in Japan. METHODS: We retrospectively analyzed data of patients with breast cancer aged ≥ 70 years who underwent breast cancer surgery in eight hospitals between 2008 and 2013. Clinical treatment and follow-up data were obtained from the patients' medical electric records. RESULTS: A total of 1095 patients were enrolled, of which 905 were included in the initial non-matched analysis. The median age and follow-up period were 75 (range 70-93) and 6.3 years, respectively. Of these patients, 127 (14%) received adjuvant chemotherapy (Chemo group) while the remaining 778 (86%) did not (Control group). The Chemo group was younger (mean age in years 73 vs 76; P < 0.0001), had a larger pathological tumor size (mean mm 25.9 vs 19.9; P < 0.0001), and more metastatic axillary lymph nodes (mean numbers 2.7 vs 0.7; P < 0.0001) than the Control group. The disease-free survival (DFS) and overall survival (OS) did not differ significantly between the two groups (P = 0.783 and P = 0.558). After matched analyses, DFS was found to be significantly prolonged with adjuvant chemotherapy (P = 0.037); however, OS difference in the matched cohort was not statistically significant (P = 0.333). CONCLUSION: The results showed that adjuvant chemotherapy was associated with a reduced risk of recurrence, but survival benefits were limited.

Successful management of pelvic recurrence of MSI-High endometrial cancer by total pelvic exenteration followed by administration of pembrolizumab:A case report.

Surgery can be curative treatment for pelvic locoregional recurrence of endometrial cancer; however, a cure is contingent on complete resection. Here, we report the case of a patient in whom recurrent endometrial tumor remained in the pelvis after resection; long-term control was achieved with postoperative administration of pembrolizumab.The patient had recurrent endometrial cancer of stage IA and was treated with chemotherapy and radiation, but tumor persisted in the pelvic cavity. We therefore attempted total pelvic exenteration, but the tumor was adherent to the pelvic wall and complete resection could not be achieved. However, postoperative administration of pembrolizumab controlled the residual tumor for more than two years without regrowth. We believe that since the resected tumor was MSI-High, the residual tumor responded well to pembrolizumab. It is not known whether cytoreductive surgery contributes to a long-term response to pembrolizumab, but at least in our patient, pembrolizumab appeared to be a very effective drug therapy for MSI-High endometrial cancer that was refractory to chemotherapy and radiotherapy.

A mass spectrometric method for in-depth profiling of phosphoinositide regioisomers and their disease-associated regulation.

Phosphoinositides are a family of membrane lipids essential for many biological and pathological processes. Due to the existence of multiple phosphoinositide regioisomers and their low intracellular concentrations, profiling these lipids and linking a specific acyl variant to a change in biological state have been difficult. To enable the comprehensive analysis of phosphoinositide phosphorylation status and acyl chain identity, we develop PRMC-MS (Phosphoinositide Regioisomer Measurement by Chiral column chromatography and Mass Spectrometry). Using this method, we reveal a severe skewing in acyl chains in phosphoinositides in Pten-deficient prostate cancer tissues, extracellular mobilization of phosphoinositides upon expression of oncogenic PIK3CA, and a unique profile for exosomal phosphoinositides. Thus, our approach allows characterizing the dynamics of phosphoinositide acyl variants in intracellular and extracellular milieus.

Significance of HER2 protein examination in ductal carcinoma in situ.

BACKGROUND: HER2 expression is routinely checked in ductal carcinoma in situ, as in invasive ductal carcinoma. However, the effect of HER2 status in ductal carcinoma in situ on the development of malignancy and the significance of overexpression of HER2 are still not clear. MATERIALS AND METHODS: We experienced 103 cases that were diagnosed as pure ductal carcinoma in situ from operative specimens in the 2-y period from 2006 to 2007. We examined their HER2 status and other markers. We added 38 cases of ductal carcinoma in situ with small invasive disease 5mm or less in diameter as subjects. We also examined how accurately HER2 status in biopsy specimens predicted the existence of an invasive component. RESULTS: In pure ductal carcinoma in situ, tumors that were comedo type, high grade, or ER negative showed a high frequency of HER2 overexpression. In cases with small invasion, HER2 expression was higher than that in pure ductal carcinoma in situ. Among cases that were diagnosed as ductal carcinoma in situ by biopsy, 28% had invasive disease in operative specimens. In tumors that were palpable, large, or expressed HER2 3+ in biopsy samples, invasive disease was frequently observed in operative specimens. CONCLUSIONS: Overexpression of HER2 in ductal carcinoma in situ might not always be necessary for progression to invasive ductal carcinoma. To clarify the significance of HER2 examination in DCIS, further investigations of the potential for invasive ductal carcinoma and the prognosis are still needed.

Decreased ER dependency after acquired resistance to CDK4/6 inhibitors.

BACKGROUND: Cyclin-dependent kinase (CDK) 4/6 inhibitors represent a significant advancement in the treatment of estrogen receptor (ER)-positive human epidermal growth factor receptor 2-negative advanced breast cancer. However, mechanisms of alterations after acquired resistance to CDK4/6 inhibitors and the optimal treatment options are still not established. METHODS: Abemaciclib-resistant cell lines were established from the models of estrogen deprivation-resistant cell lines which retained ER expression and activated ER function derived from MCF-7 breast cancer cell lines. Ribocilib-resistant cell lines were established in the same method as previously reported. RESULTS: Both abemaciclib- and ribociclib-resistant cell lines showed decreased ER expression. ER transcriptional activity was maintained in these cell lines; however, the sensitivity to 4-hydroxytamoxifen and fulvestrant was almost completely lost. These cell lines did not exhibit any ERα gene mutation. Abemaciclib-resistant cell lines demonstrated low sensitivity to other CDK4/6 inhibitors; sensitivities to PI3K inhibitor, mTOR inhibitor, and chemotherapeutic drugs were maintained. CONCLUSIONS: Dependence on ER signaling appears to decrease after the development of acquired resistance to CDK4/6 inhibitors. Further, CDK4/6 inhibitor-resistant cells acquired cross-resistance to other CDK4/6 inhibitors, PI3K/Akt/mTOR inhibitor therapy and chemotherapeutic drugs might serve as optimal treatment options for such breast cancers.

Risk of immunotherapy-related narcolepsy in genetically predisposed patients: a case report of narcolepsy after administration of pembrolizumab.

BACKGROUND: Immune-related adverse events associated with immune checkpoint therapy cause autoimmune disease-like symptoms. People who carry specific genotypes or haplotypes of human leucocyte antigen (HLA) are known to be predisposed to develop autoimmune diseases including narcolepsy. Immunotherapy could be a trigger to develop narcolepsy in predisposing HLA positive patients. CASE PRESENTATION: A 66-year-old woman with stage IVB endometrial carcinosarcoma experienced daytime sleepiness and temporary muscle weakness 14 days after the administration of an immune checkpoint inhibitor, pembrolizumab. These were consistent with the main symptoms of narcolepsy with cataplexy. This patient carried a highly predisposing HLA haplotype for narcolepsy; HLA-DQB1*06:02, DRB1*15:01, DQA1*01:02 and DRB5*01:01:01. A hypocretin-1/orexin-A concentration in the patient's cerebrospinal fluid was low at 9.6 pg/mL in ELISA, and 155.5 pg/mL in radioimmunoassay that was below the normal level of 200 pg/mL. Therefore, she was diagnosed with narcolepsy tentatively according to the International Classification of Sleep Disorders, third edition diagnostic criteria for narcolepsy. The onset of narcolepsy in the 60s is very rare, and narcoleptic symptoms in our patient were likely to be caused by pembrolizumab. CONCLUSIONS: This case suggests that treatment with immune checkpoint inhibitors potentially causes narcolepsy in genetically predisposed patients.