Risk Factors for Eribulin-induced Severe Neutropenia in Patients With Recurrent Breast Cancer.

BACKGROUND/AIM: Eribulin is an effective chemotherapeutic agent for advanced and metastatic breast cancer. However, severe neutropenia occurs in 30-40% of patients and interferes with the recommended treatment schedule. Neutropenia is a major cause of treatment interruptions, delays, or even relative dose reductions. This study aimed to examine the risk factors for severe neutropenia after eribulin treatment. PATIENTS AND METHODS: We retrospectively evaluated 263 patients with metastatic breast cancer who had received eribulin therapy. Risk factors for severe neutropenia in the first cycle were evaluated. RESULTS: Severe neutropenia in cycle 1 occurred in 50% of the patients. Multivariate analysis suggested six risk factors for severe neutropenia: low baseline neutrophil count and body mass index, high aspartate aminotransferase and bilirubin levels, creatinine clearance (CrCl) less than 50 ml/min, and eribulin dose of 1.4 mg/m2 Conclusion: This is one of the few studies to simultaneously examine both hepatic and renal functions in relation to severe neutropenia induced by eribulin. We have provided important information to support the close monitoring of patients with these risk factors and subsequent dosage adjustments, if necessary.

Treatment with trastuzumab deruxtecan in patients with HER2-positive breast cancer and brain metastases and/or leptomeningeal disease (ROSET-BM).

Therapeutic options for breast cancer patients with brain metastases (BM)/leptomeningeal carcinomatosis (LMC) are limited. Here, we report on the effectiveness and safety of trastuzumab deruxtecan (T-DXd) in human epidermal growth factor receptor 2-positive breast cancer patients with BM. Data were analyzed for 104 patients administered T-DXd. Overall response rate (ORR), progression-free survival (PFS), overall survival (OS), intracranial (IC)-ORR, and IC-PFS were evaluated. ORR by investigator assessment was 55.7% (total population). Median PFS was 16.1 months; 12-month OS rate was 74.9% (total population). Median time-to-treatment failure was 9.7 months. In 51 patients with BM imaging, IC-ORR and median IC-PFS by independent central review were 62.7% and 16.1 months, respectively. In 19 LMC patients, 12-month PFS and OS rates were 60.7% and 87.1%, respectively. T-DXd showed effectiveness regarding IC-ORR, IC-PFS, PFS, and OS in breast cancer patients with BM/active BM, and sustained systemic and central nervous system disease control in LMC patients.Trial Registration: UMIN000044995.

Real-World Predictors of Severe Neutropenia Associated with Palbociclib and Endocrine Therapy for Metastatic Breast Cancer in Japanese Patients.

Therapy for patients of metastatic breast cancer based on palbociclib, a cyclin-dependent kinase 4/6 inhibitor, has been approved in Japan. However, the risk factors for palbociclib-induced severe neutropenia in Japanese patients are rarely reported. Hence, the present study is aimed to identify the risk factors for adverse events requiring palbociclib dose reduction or discontinuation, and to identify the factors necessary to identify a more stable strategy for treatment continuation. This retrospective cohort analysis included patients with advanced breast cancer treated with 125 mg/d palbociclib. We demonstrated that severe neutropenia required significant dose reduction or therapy cessation. Most (77%) of the patients had severe neutropenia within the three courses. Risk factors for grade 3 or higher included low neutrophil counts (< 3250 /µL) before treatment [odds ratio (OR) = 9.10, 95% confidence interval (CI) (2.80-29.41), p < 0.001] and high age-adjusted Charlson comorbidity index (> 9) [OR = 1.64, 95% CI (1.09-2.48), p = 0.018]. Thus, low baseline neutrophil counts and high values for Age-adjusted Charlson comorbidity index are prospective predictive markers for palbociclib-induced severe neutropenia.

Clinical Management of Potential Toxicity of Abemaciclib and Approaches to Ensure Treatment Continuation.

INTRODUCTION: The association between abemaciclib dose reduction and treatment adherence is not clear. In this study, we examined real-world data of Japanese patients with advanced breast cancer (ABC) to determine how abemaciclib dose reduction is related to treatment continuation. METHODS: This retrospective observational study involved 120 consecutive patients with ABC who received abemaciclib from December 2018 to March 2021. The time to treatment failure (TTF) was estimated using the Kaplan-Meier method. Univariate and multivariate analyses were performed to identify factors associated with a TTF of >365 days (TTF365). RESULTS: According to the dose reduction during treatment, the patients were classified into 100, 200, and 300 mg/day abemaciclib groups. The 300 mg/day group had a TTF of 7.4 months, whereas the 100 and 200 mg/day groups had significantly longer TTFs (17.9 and 17.3 months, respectively; P = 0.0002). In this study, relative to the 300 mg/day arm, TTF was improved in 200mg/day arm and 100 mg/day arm (hazard ratio [HR], 0.55; 95% confidence interval [CI], 0.33-0.93) and [HR], 0.37; 95% CI, 0.19-0.74). For patients who received 300mg/day of abemaciclib dose arm, 200mg/day, and 100mg/day, the median TTF was 7.4 ,17.9 and 17.3 months. The frequently reported adverse effects (AEs) were anemia, increased blood creatinine levels, diarrhea, and neutropenia (90%, 83%, 83%, and 75% of the patients, respectively). Neutropenia, fatigue, and diarrhea were the top AEs causing dose reduction. A multivariate analysis that examined factors associated with achieving TTF 365 confirmed that dose down was an important factor (odds ratio: 3.95, 95% confidence interval: 1.68-9.36, P = 0.002). CONCLUSIONS: In this study, the 100 and 200 mg/day groups had a longer TTF than the 300 mg/day group, and dose reduction was identified as an important factor in achieving longer TTF.

Programmed death ligand 1-positive immune cells in primary tumor or metastatic axillary lymph nodes can predict prognosis of triple-negative breast cancer even when present at < 1% in the tumor region.

BACKGROUND: The efficacy of pre-operative systemic treatment (PST) combined with immune checkpoint inhibition (ICI) for triple-negative breast cancer (TNBC) has been recognized recently as being independent of the degree of programmed death ligand-1 (PD-L1) positivity of infiltrating immune cells, especially for patients with axillary lymph node metastasis (ALNM). METHODS: TNBC patients with ALNM were treated surgically between 2002 and 2016 in our facility (n = 109), of whom 38 received PST before resection. The presence of tumor-infiltrating lymphocytes (TILs) expressing CD3, CD8, CD68, PD-L1 (detected by antibody SP142) and FOXP3 at primary and metastatic LN sites was quantified. RESULTS: The size of invasive tumor and the number of metastatic axillary LN were confirmed as prognostic markers. The numbers of both CD8+ and FOXP3+ TILs at primary sites were also recognized as prognostic markers, especially for overall survival (OS) (CD8, p = 0.026; FOXP3, p < 0.001). The presence of CD8+, FOXP3+ and PD-L1+ cells was better maintained in LN after PST and may contribute to improved antitumor immunity. Provided they were present as clusters of ≥ 70 positive cells, even < 1% of immune cells expressing PD-L1 at primary sites predicted a more favorable prognosis for both disease-free survival (DFS) (p = 0.004) and OS (p = 0.020). This was the case not only for 30 matched surgical patients, but also in all 71 surgical only patients (DFS: p < 0.001 and OS: p = 0.002). CONCLUSIONS: PD-L1+ , CD8+ or FOXP3+ immune cells in the tumor microenvironment (TME) at both primary and metastatic sites are significant on prognosis, which could be a clue to expect the potential for better responses to the combination of chemotherapy and ICI, especially for patients with ALNM.

Significance of prostate/pancreatic/skin cancer family history for detecting BRCA2 pathogenic variant careers among patients with breast cancer.

BACKGROUND: When considering BRCA1/2 genetic testing for diagnosis of hereditary breast and ovarian cancer (HBOC), family history (FH) of breast and ovarian cancer is commonly considered. However, FH of other HBOC-related cancers, such as prostate, pancreatic, and skin cancer (malignant melanoma), is often overlooked. METHODS: Among 945 patients who received genetic testing of BRCA1/2 at our hospital between October 2010 and September 2021, we compared the FH of 123 patients diagnosed with HBOC and 669 other patients who had breast cancer and had a documented FH. This study focused on the FH of HBOC-related cancers such as breast, ovarian, prostate, pancreatic, and skin cancer, as well as colorectal, gastric, liver, lung, and uterine cancers, which are common among Japanese, and other cancers. RESULTS: FH of prostate, pancreatic, and skin cancer was significantly higher in the BRCA2 pathogenic variant (PV) cases than in the wild-type (WT) cases. The mean number of family members are as follows: BRCA1 PV/ BRCA2 PV/ WT; prostate cancer: 0.05/ 0.34/ 0.09 (P < 0.0001, Kruskal-Wallis multiple comparisons test), pancreatic cancer: 0.13/ 0.21/ 0.10 (P = 0.01637), and skin cancer: 0.03/ 0.07/ 0.01 (P = 0.00129), respectively. CONCLUSIONS: When considering BRCA1/2 genetic testing, FH of prostate, pancreatic, and skin cancers may also be examined as HBOC-related cancers to provide testing for patients who would benefit from it. However, further studies for the association between skin cancer and HBOC will be required because it has not been reported in Japan.

The therapeutic candidate for immune checkpoint inhibitors elucidated by the status of tumor-infiltrating lymphocytes (TILs) and programmed death ligand 1 (PD-L1) expression in triple negative breast cancer (TNBC).

BACKGROUND: The status of tumor-infiltrating lymphocytes (TILs) is a prognostic factor for triple negative breast cancer (TNBC). Recent studies have shown that programmed cell death 1 (PD-1) or programmed death ligand 1 (PD-L1) is expressed on T lymphocytes or tumor cells modulating antitumor immunity. The regulation of immune checkpoints between tumor cells and T lymphocytes may serve as a target for improvement of TNBC prognosis. We investigated TILs and PD-L1 status in TNBCs before or after preoperative systemic therapy (PST) to elucidate the clinical significance of PD-L1 expression. METHODS: Ninety patients received PST, and materials of core needle biopsies (CNB) taken before PST were available for 32 patients. TILs were scored as "% stromal", and tumors were defined as High-TILs (≥30%) or Low-TILs (<30%). The expression of PD-L1 was assessed by immunohistochemistry. RESULTS: TILs status in CNB is significant in pathological therapeutic grade: 1 vs. 2 or 3 (p = 0.0359). Disease-free survival (DFS) in patients with Low-TIL tumors were significantly worse than those with High-TIL tumors (p = 0.0383), but overall survival (OS) showed no significance (p = 0.0772). However, in patients with Low-TIL tumors, both DFS and OS in patients with High-PD-L1 expression were extremely unfavorable than in patients with Low-PD-L1 expression (p = 0.0032, p = 0.0002). CONCLUSION: The patients with TNBCs with combined Low-TILs and High-PD-L1 status in pre-PST situation showed unfavorable prognosis. The subset of TNBCs with Low-TILs and High-PD-L1 status could be the therapeutic target for immune checkpoint inhibitor.

Durable complete response in HER2-positive breast cancer: a multicenter retrospective analysis.

PURPOSE: Though advanced and metastatic epidermal growth factor receptor 2 (HER2)-positive disease is not curable, a small proportion of patients with HER2-positive metastatic breast cancer remain in prolonged complete remission with anti-HER2 treatment. We hypothesized that some cases of HER2-positive metastatic breast cancer may be curable. In this large, multicenter retrospective study, we aimed to assess the long-term outcomes for patients with a durable response to trastuzumab. METHODS: We retrospectively evaluated the data of patients diagnosed with HER2-positive metastatic breast cancer who received trastuzumab for more than 2 years as the first-line treatment. Patients diagnosed between April 1, 2001 and December 31, 2014 at 19 institutions in Japan were included in the analysis. From 124 potential subjects, 16 were excluded and 108 were evaluated. RESULTS: The median follow-up length was 7.7 years. Disease progression occurred in 44/108 (40.7%) patients and 13/108 (12%) patients died. The median progression-free survival was 11.2 years, and as more than 80% of patients were alive 10 years after metastatic breast cancer diagnosis. Of the 108 patients, 57 achieved a clinical complete response. Trastuzumab therapy was interrupted for 27 (47.4%) of these patients (based on the doctor's recommendation for 19 patients, owing to adverse events for 4 patients, owing to unknown reasons for 3 patients, and at the request of 1 patient). Disease progression occurred in 4 of the 27 patients after the interruption of trastuzumab treatment. The median duration of trastuzumab therapy for all 27 patients was 5.1 years (0.9-9.3 years). CONCLUSION: We found that some patients showed no evidence of disease after the interruption of trastuzumab therapy. Discontinuation of maintenance trastuzumab in this patient population after a limited time should be explored cautiously while awaiting a global collaborative effort for a randomized trial.

[Safety and Tolerance of Dose-Dense Epirubicin and Cyclophosphamide (EC) with Pegfilgrastim for Japanese Patients with Early Breast Cancer].

With the approval of pegfilgrastim, the use of dose-dense epirubicin and cyclophosphamide (EC) for breast cancer has become acceptable in Japan. Thus, we aimed to evaluate its safety and tolerability in Japanese patients. Nine breast cancer patients with a high risk of preoperative or postoperative recurrence received EC therapy(epirubicin 90 mg/m(2) and cyclo- phosphamide 600 mg/m(2))for 4 cycles every 2 weeks in combination with a subcutaneous injection of pegfilgrastim (3.6 mg) on day 2 of each cycle. Treatment was discontinued in 1 and extended in 1 of the 9 patients, and the mean relative dose intensity(RDI)was good at 0.93. No serious adverse events were observed, indicating good tolerability. The regimen has potential for use in cases in which the treatment dose needs to be increased. grade 4 neutropenia was observed in all the 9 patients on day 8, with 6 patients developing febrile neutropenia. In Japan, data on changes in neutrophil count associated with pegfilgrastim administration under anthracycline-based chemotherapy are currently insufficient, and further study is required.

Fulvestrant 500 mg in postmenopausal patients with metastatic breast cancer: the initial clinical experience.

BACKGROUND: Fulvestrant 500 mg is currently approved for the treatment of postmenopausal women with hormone receptor-positive metastatic breast cancer after failure of prior endocrine therapies. METHODS: A total of 117 postmenopausal women with metastatic breast cancer, who experienced progression after previous endocrine therapies, were treated with fulvestrant 500 mg between January 2012 and June 2014. Clinical response, time to progression (TTP) and adverse events were investigated. RESULTS: Ninety-nine patients had recurrent breast cancer and 18 patients had stage IV disease. Patients had received a median of two endocrine therapies and a median of two chemotherapies, prior to fulvestrant. There were 10 patients with partial response, 39 patients with long stable disease, 18 patients with stable disease, and 50 patients with progressive disease, so that the objective response rate was 8.5 %, with a clinical benefit rate of 41.9 %. The median TTP was 6.1 months. The absence of liver metastases, a small number of previous chemotherapies, and the longer duration of first-line endocrine therapy were positively correlated with TTP in univariate analysis. In multivariate analysis, a significant association was observed between TTP and duration of first-line endocrine therapy. Serious adverse events were observed in one patient with pulmonary embolism and in one patient with psychiatric symptoms. CONCLUSIONS: Fulvestrant 500 mg is an effective and well-tolerated treatment for postmenopausal women with metastatic breast cancer that had progressed after prior endocrine therapies. Patients with acquired resistance to endocrine therapies might be good candidates for fulvestrant therapy regardless of the number of prior endocrine treatments.

Prognostic significance of pathologic complete response and Ki67 expression after neoadjuvant chemotherapy in breast cancer.

BACKGROUND: Recent studies have indicated that response to chemotherapy and the prognostic impact of a pathologic complete response (pCR) after neoadjuvant chemotherapy differ among breast cancer subtypes. METHODS: Women with Stage I to III breast cancer treated with anthracycline and taxane-based neoadjuvant chemotherapy (four cycles of docetaxel every 3 weeks followed by four cycles of FEC every 3 weeks) between 2006 and 2011 were retrospectively analyzed. Trastuzumab was concurrently added to docetaxel for HER2-positive breast cancer. Expression of estrogen receptor (ER), progesterone receptor (PgR), HER2, and Ki67 was examined by immunohistochemistry in pre- and post-treatment specimens. Predictive factors for neoadjuvant chemotherapy and prognosis were analyzed by breast cancer subtype. RESULTS: Of 64 patients, 30 (47 %) were ER-positive (ER+) HER2-negative (HER2-), including eight as luminal A (Ki67 labeling index (LI) <14 %) and 22 as luminal B (Ki67 LI ≥ 14 %) subtypes, 11 (17 %) were ER+ HER2-positive (HER2+), 12 (19 %) were ER-negative (ER-) HER2+, and 11 (17 %) were ER- HER2-. The clinical response rates were significantly higher in luminal B, ER+ HER2+, and ER- HER2+ subtypes compared with luminal A subtype. Patients whose tumors contained high Ki67 expression effectively responded to neoadjuvant chemotherapy. Ki67 LI was a predictive marker for pCR, and all patients whose tumors achieved pCR are currently disease-free. Furthermore, high Ki67 expression in post-treatment tumors was strongly correlated with poor disease-free and overall survival regardless of subtype. CONCLUSIONS: It is necessary to establish additional strategies to improve survival for patients whose residual tumors show high Ki67 expression after neoadjuvant chemotherapy.

Prognostic significance of pre-treatment neutrophil: lymphocyte ratio in Japanese patients with breast cancer.

BACKGROUND: The neutrophil:lymphocyte ratio (NLR) has been reported to reflect systemic inflammation and to have independent prognostic value for patients with various cancers. In this study, we analyzed the association between NLR and clinicopathological factors and verified the significance of NLR as a prognostic factor for Japanese patients with breast cancer. PATIENTS AND METHODS: A total of 167 Japanese female patients with stage I-III breast cancer were retrospectively recruited into this study. Associations with clinicopathological factors and NLR were assessed, and disease-free survival and breast cancer-specific survival were estimated. RESULTS: In multivariate analysis, lymph node metastases and NLR were significantly associated with disease-free survival and breast cancer-specific survival. NLR was significantly higher in patients with lower body-mass index. CONCLUSION: Preoperative NLR may be an independent prognostic factor for survival in Japanese patients with breast cancer. Reduction of body mass index has been implicated in NLR elevation, particularly in postmenopausal women.

Differential expression of progesterone receptor, FOXA1, GATA3, and p53 between pre- and postmenopausal women with estrogen receptor-positive breast cancer.

Estrogen receptor (ER) is essential for estrogen-dependent growth, and its level of expression is considered a crucial determinant of response to endocrine therapy and prognosis in ER-positive breast cancer. On the other hand, the clinical role of progesterone receptor (PgR) in ER-positive breast cancer remains controversial, although testing of PgR by immunohistochemistry (IHC) has become routine. Recent studies indicated that plasma estradiol levels were related to the expression levels of estrogen-responsive genes in ER-positive breast cancer tissues in both pre- and postmenopausal women. In this study, we analyzed the expression levels of estrogen-responsive genes (PgR and TFF1), a progesterone-responsive gene (RANKL), ER-related genes (FOXA1 and GATA3), HER2, Ki67 and p53 in ER-positive, HER2-negative breast cancer tissues by IHC. Correlations between the expression levels of these molecular markers and clinicopathological factors, including prognosis, were compared between pre- and postmenopausal women. Serum levels of estrone, estradiol, progesterone, and testosterone were also measured. Expression levels of PgR, TFF1, RANKL, and GATA3 were significantly higher in premenopausal women than in postmenopausal women. Serum estradiol levels were positively correlated with Ki67 labeling index (LI) in premenopausal women, but not in postmenopausal women. High expression of FOXA1 and GATA3 was significantly associated with improved disease-free survival in premenopausal women, but not in postmenopausal women, whereas high expression of PgR and low expression of p53 were significantly correlated with the improved disease-free survival in postmenopausal women, but not in premenopausal women. Moreover, the best cutoff points of Ki67 LI for disease-free survival were 30 % for premenopausal women and 14 % for postmenopausal women. Expression levels of ER, TFF1, and RANKL were not associated with the disease-free survival in either pre- or postmenopausal women. Our results suggest that the mechanisms of development and estrogen-dependent growth of ER-positive breast cancer might differ according to menopausal status.

p53 accumulation is a strong predictor of recurrence in estrogen receptor-positive breast cancer patients treated with aromatase inhibitors.

Aromatase inhibitors have played a central role in endocrine therapy for estrogen receptor (ER)-positive breast cancer in postmenopausal women. However, factors predictive of the efficacy of aromatase inhibitors, and prognostic factors, both for early and late recurrence in women treated with adjuvant aromatase inhibitors have not been identified. Whole genome analysis identified that a TP53 gene mutation exists in ER-positive breast cancers, although the frequency of TP53 gene mutation in luminal tumors is lower compared with basal-like or human epidermal growth factor receptor type 2 (HER2)-positive breast cancers. We examined expression of p53, as well as ER, progesterone receptor, HER2 and Ki-67 using immunohistochemistry in postmenopausal ER-positive breast cancer patients who were treated with aromatase inhibitors as adjuvant endocrine therapy. There were 53 (21%) tumors that contained 10% or more p53-positive cells. High p53 expression was positively correlated with tumor grade, HER2 score and Ki-67 expression. Significant association was observed between disease-free survival and high p53 expression in multivariate analysis (P < 0.0001). Compared with women without recurrence, women with early recurrence had significantly higher p53 expression (P < 0.0001), as did women with late recurrence (P = 0.037). The present study demonstrates that p53 accumulation is a strong predictor of both early and late recurrence in ER-positive breast cancer patients treated with aromatase inhibitors as adjuvant endocrine therapy. TP53 gene alteration might be a key biological characteristic of ER-positive breast cancer.

[Safety and tolerance of docetaxel (especially 75 mg/m2) with cyclophosphamide (TC therapy) as adjuvant chemotherapy for Japanese patients with operable breast cancer].

The safety and tolerance of docetaxel (especially 75 mg/m/2) plus cyclophosphamide (600 mg/m2) (TC therapy) as adjuvant chemotherapy for Japanese patients (n=47) with operable breast cancer was evaluated. Among 47 patients who received TC therapy, 38 patients (80.8%) were treated as scheduled for 4 courses every three weeks, and 6 patients (12.8%) were dose-reduced or the interval between courses was extended due to neutropenia or wound infection. Three patients (6.4%) quit TC therapy due to stomatitis or skin toxicities of grade 3. Although febrile neutropenia of grade 3 or 4 was observed in 2 patients (4.3%), TC therapy could be prescribed for these patients. Non-hematological side effects(such as edema, myalgia and arthralgia), occurred in relatively many cases, but were not remarkable. From these results, TC therapy (75/600 mg/m2) is considered to be a safe and tolerable regimen in Japanese patients operated for breast cancer.

[Evaluation of low-dose FP therapy as adjuvant therapy for gastric cancer].

In the present study, we demonstrate the result of low-dose FP treatment as an adjuvant therapy for 30 patients of stage II or more progressive gastric cancer. 5-FU and CDDP were injected intravenously for 10 days from day 1 through day 5, and day 8 through 12 for 2 weeks at a dose of 250 mg/body and 10 mg/body, or for 14 days at a dose of 250 mg/m2/day and 5 mg/m2/day, respectively. Patients were excluded if they received less than 80% of the respective doses in a course of treatment by the protocol. This constituted a course of chemotherapy, which was repeated every 4 weeks. Grade 3 neutropenia was observed in one case. Other toxicities were anorexia, nausea, weight loss, diarrhea, general fatigue and elevation of serum creatinine, but they were not so severe. The two-year survival rate was 100% in cur A cases, 85% in cur B, and 0% in cur C. The median survival time of the cur C patients was 10 months. These results indicate that low-dose FP therapy is safe and recommendable for cur A and cur B patients. However, other treatment methods such as sequential chemotherapy are needed for cur C gastric cancer patients.

Characterization of chitinase genes from an alkaliphilic actinomycete, Nocardiopsis prasina OPC-131.

An alkaliphilic actinomycete, Nocardiopsis prasina OPC-131, secretes chitinases, ChiA, ChiB, and ChiB Delta, in the presence of chitin. The genes encoding ChiA and ChiB were cloned and sequenced. The open reading frame (ORF) of chiA encoded a protein of 336 amino acids with a calculated molecular mass of 35,257 Da. ChiA consisted of only a catalytic domain and showed a significant homology with family 18 chitinases. The chiB ORF encoded a protein of 296 amino acids with a calculated molecular mass of 31,500 Da. ChiB is a modular enzyme consisting of a chitin-binding domain type 3 (ChtBD type 3) and a catalytic domain. The catalytic domain of ChiB showed significant similarity to Streptomyces family 19 chitinases. ChiB Delta was the truncated form of ChiB lacking ChtBD type 3. Expression plasmids coding for ChiA, ChiB, and ChiB Delta were constructed to investigate the biochemical properties of these recombinant proteins. These enzymes showed pHs and temperature optima similar to those of native enzymes. ChiB showed more efficient hydrolysis of chitin and stronger antifungal activity than ChiB Delta, indicating that the ChtBD type 3 of ChiB plays an important role in the efficient hydrolysis of chitin and in antifungal activity. Furthermore, the finding of family 19 chitinase in N. prasina OPC-131 suggests that family 19 chitinases are distributed widely in actinomycetes other than the genus Streptomyces.