Inclusion Criteria:

   - Patients must have unresectable or metastatic, histologically confirmed low or
   intermediate grade (Klimstra Criteria) pancreatic neuroendocrine tumor (PNET) with
   radiological evidence of disease progression since last treatment

   - Refractory disease to treatment with an mTOR inhibitor

   - Patients with uncontrolled intercurrent illness including, but not limited to, ongoing
   or active infection, symptomatic congestive heart failure, unstable angina pectoris,
   cardiac arrhythmia, or psychiatric illness/social situations that would limit
   compliance with study requirements, are ineligible

   - Disease that is currently not amenable to surgery, radiation, or combined modality
   therapy with curative intent

   - Patients must not have poorly differentiated neuroendocrine carcinoma, high-grade
   neuroendocrine carcinoma, adenocarcinoid, goblet cell carcinoid and small cell
   carcinoma

   - Patients must have measurable disease

   - Documented radiological evidence for disease progression (measurable or nonmeasurable)
   =< 12 months prior to enrollment

      - NOTE: If patient has had previous radiation to the marker lesion(s), there must
      be evidence of progression since the radiation; at least one measurable lesion as
      per Response Evaluation Criteria in Solid Tumors (RECIST)

   - Prior or concurrent therapy with somatostatin analogue (SSA) is permitted; a stable
   dose at least 2 months prior to study start and must continue on the stable dose while
   receiving study treatment; SSA is not considered as systemic treatment

   - Recovered from adverse events to grade 1 or less toxicity according to Common
   Terminology Criteria for Adverse Events version 4.0 (CTCAE 4.0) due to agents
   administered previously

      - NOTE: Chemotherapy-induced alopecia and grade 2 neuropathy are acceptable

   - Patients must have Eastern Cooperative Oncology Group (ECOG) performance status of 0-1

   - Patients must be able to swallow intact capsules

   - Leukocytes >= 3,000/mm^3 (within less than or equal to 14 days prior to registration)

   - Absolute neutrophil count (ANC) >= 1.5 x 10^9/L (within less than or equal to 14 days
   prior to registration)

   - Hemoglobin >= 10 g/dL (within less than or equal to 14 days prior to registration)

   - Platelets >= 100 x 10^9/L (within less than or equal to 14 days prior to registration)

   - Total serum bilirubin =< institutional upper limit of normal (ULN) (within less than
   or equal to 14 days prior to registration)

   - Alanine aminotransferase (ALT) and aspartate aminotransferase (AST) =< 2.5 x ULN
   (within less than or equal to 14 days prior to registration)

   - Serum creatinine =< 1.5 X institutional ULN and creatinine clearance >= 60 ml/min
   (within less than or equal to 14 days prior to registration)

      - NOTE: Creatinine clearance must be calculated using the Cockcroft-Gault equation

   - Glycosylated hemoglobin (HbA1c) < 7.0% (within less than or equal to 14 days prior to
   registration)

   - Fasting serum glucose =< 130 mg/dL (within less than or equal to 14 days prior to
   registration)

   - Fasting triglycerides =< 300 mg/dL (within less than or equal to 14 days prior to
   registration)

   - Diabetics are allowed if:

      - Fasting blood glucose (FBG) =< 130 mg/dL (mmol/L), OR

      - HbA1c =< 7%

   - Women must not be pregnant or breast-feeding due to potential harm to the fetus from
   MLN0128 (TAK-228); all females of childbearing potential must have a blood test or
   urine study within 7 days of registration to rule out pregnancy; a female of
   childbearing potential is any woman, regardless of sexual orientation or whether they
   have undergone tubal ligation, who meets the following criteria: 1) has not undergone
   a hysterectomy or bilateral oophorectomy; or 2) has not been naturally postmenopausal
   for at least 24 consecutive months (i.e., has had menses at any time in the preceding
   24 consecutive months)

   - Women of child-bearing potential and men must agree to practice 1 highly effective
   method of contraception and 1 additional effective (barrier) method of contraception,
   at the same time, from the time of signing the informed consent through 90 days (for
   female patients) and 120 day (for male patients) after the last dose of study drug, or
   agree to completely abstain from heterosexual intercourse; should a woman become
   pregnant or suspect she is pregnant while she or her partner is participating in this
   study, she should inform her treating physician immediately; men must agree not to
   donate sperm during the course of this study or within 120 days after receiving their
   last dose of study drug

   - Patients who have a history of brain metastasis are eligible for the study provided
   that all the following criteria are met:

      - Brain metastases which have been treated

      - No evidence of disease progression for >= 3 months before the first dose of study
      drug

      - No hemorrhage after treatment

      - Off-treatment with dexamethasone for 4 weeks before administration of the first
      dose of TAK-228

      - No ongoing requirement for dexamethasone or anti-epileptic drugs

   - Voluntary written consent must be given before performance of any study related
   procedure not part of standard medical care, with the understanding that consent may
   be withdrawn by the patient at any time without prejudice to future medical care

Exclusion Criteria:

   - Patient is INELIGIBLE if patient discontinued prior mTOR inhibitor due to toxicity

   - Patients must NOT have radiotherapy, or major surgery or active drug therapy for pNET
   (SSA permitted) within 4 weeks prior to study treatment start

   - Patient must NOT have had previous treatment with any PI3K or AKT inhibitor

   - NO hepatic artery embolization or cryoablation/radiofrequency ablation of hepatic
   metastasis within 2 months of study treatment start

   - Patients must NOT have previous or concurrent malignancy within 2 years; exceptions
   are made for patients who meet any of the following conditions:

      - Adequately treated basal cell or squamous cell skin cancer, superficial bladder
      cancer OR

      - Adequately treated stage I or II cancer currently in complete remission, or any
      other cancer that has been in complete remission for at least 2 years

   - No more than 3 prior systemic treatment regimens for advanced PNET

   - Patients with a history of the following within =< 6 months of study entry are NOT
   eligible:

      - Ischemic myocardial event, including angina requiring therapy and artery
      revascularization procedures

      - Ischemic cerebrovascular event, including transient ischemic attack (TIA) and
      artery revascularization procedures

      - Requirement for inotropic support (excluding digoxin) or serious (uncontrolled)
      cardiac arrhythmia (including atrial flutter/fibrillation, ventricular
      fibrillation or ventricular tachycardia)

      - New York Heart Association (NYHA) class III or IV heart failure

      - Pulmonary embolism

   - Patients with known significant active cardiovascular or pulmonary disease at the time
   of study entry are INELIGIBLE including:

      - Uncontrolled hypertension (i.e., systolic blood pressure >180 mm Hg, diastolic
      blood pressure > 95 mm Hg); use of anti-hypertensive agents to control
      hypertension before cycle1 day 1 is allowed

      - Pulmonary hypertension

      - Uncontrolled asthma or oxygen (O2) saturation < 90% by arterial blood gas
      analysis or pulse oximetry on room air

      - QT syndrome, or torsades de pointes

      - Significant valvular disease; severe regurgitation or stenosis by imaging
      independent of symptom control with medical intervention, or history of valve
      replacement

      - Medically significant (symptomatic) bradycardia

      - History of arrhythmia requiring an implantable cardiac defibrillator

      - Baseline prolongation of the rate-corrected QT interval (QTc) (e.g., repeated
      demonstration of QTc interval > 480 milliseconds, or history of congenital long

   - Patients with known manifestations of malabsorption due to prior gastrointestinal (GI)
   surgery, GI disease, or for an unknown reason that may alter the absorption of MLN0128
   (TAK-228) are INELIGIBLE

   - Human immunodeficiency virus (HIV)-positive patients on combination antiretroviral
   therapy are INELGIBLE because of the potential for pharmacokinetic interactions with
   MLN0128 (TAK-228)

   - NO treatment with strong inhibitors and/or inducers of cytochrome P450 (CYP) 3A4, or
   CYP2C19 within 1 week preceding the first dose of study drug

   - NO patients receiving systemic corticosteroids (either intravenous [IV] or oral
   steroids, excluding inhalers or low-dose hormone replacement therapy) within 1 week
   before administration of the first dose of study drug

   - Patients CANNOT have daily or chronic use of a proton pump inhibitor (PPI) and/or
   having taken a PPI within 7 days before receiving the first dose of study drug